CINXE.COM

<?xml version="1.0" encoding="UTF-8"?> <rdf:RDF xmlns="http://purl.org/rss/1.0/" xmlns:dc="http://purl.org/dc/elements/1.1/" xmlns:dcterms="http://purl.org/dc/terms/" xmlns:cc="http://web.resource.org/cc/" xmlns:prism="http://prismstandard.org/namespaces/basic/2.0/" xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#" xmlns:admin="http://webns.net/mvcb/" xmlns:content="http://purl.org/rss/1.0/modules/content/"> <channel rdf:about="https://www.mdpi.com/rss/journal/universe"> <title>Universe</title> <description>Latest open access articles published in Universe at https://www.mdpi.com/journal/universe</description> <link>https://www.mdpi.com/journal/universe</link> <admin:generatorAgent rdf:resource="https://www.mdpi.com/journal/universe"/> <admin:errorReportsTo rdf:resource="mailto:support@mdpi.com"/> <dc:publisher>MDPI</dc:publisher> <dc:language>en</dc:language> <dc:rights>Creative Commons Attribution (CC-BY)</dc:rights> <prism:copyright>MDPI</prism:copyright> <prism:rightsAgent>support@mdpi.com</prism:rightsAgent> <image rdf:resource="https://pub.mdpi-res.com/img/design/mdpi-pub-logo.png?13cf3b5bd783e021?1732286508"/> <items> <rdf:Seq> <rdf:li rdf:resource="https://www.mdpi.com/2218-1997/10/12/436" /> <rdf:li rdf:resource="https://www.mdpi.com/2218-1997/10/12/435" /> <rdf:li rdf:resource="https://www.mdpi.com/2218-1997/10/12/434" /> <rdf:li rdf:resource="https://www.mdpi.com/2218-1997/10/11/433" /> <rdf:li rdf:resource="https://www.mdpi.com/2218-1997/10/11/432" /> <rdf:li rdf:resource="https://www.mdpi.com/2218-1997/10/11/431" /> <rdf:li rdf:resource="https://www.mdpi.com/2218-1997/10/11/430" /> <rdf:li rdf:resource="https://www.mdpi.com/2218-1997/10/11/429" /> <rdf:li rdf:resource="https://www.mdpi.com/2218-1997/10/11/428" /> <rdf:li rdf:resource="https://www.mdpi.com/2218-1997/10/11/427" /> <rdf:li rdf:resource="https://www.mdpi.com/2218-1997/10/11/426" /> <rdf:li rdf:resource="https://www.mdpi.com/2218-1997/10/11/425" /> <rdf:li rdf:resource="https://www.mdpi.com/2218-1997/10/11/424" /> <rdf:li rdf:resource="https://www.mdpi.com/2218-1997/10/11/423" /> <rdf:li rdf:resource="https://www.mdpi.com/2218-1997/10/11/422" /> <rdf:li rdf:resource="https://www.mdpi.com/2218-1997/10/11/421" /> <rdf:li rdf:resource="https://www.mdpi.com/2218-1997/10/11/419" /> <rdf:li rdf:resource="https://www.mdpi.com/2218-1997/10/11/420" /> <rdf:li rdf:resource="https://www.mdpi.com/2218-1997/10/11/418" /> <rdf:li rdf:resource="https://www.mdpi.com/2218-1997/10/11/417" /> <rdf:li rdf:resource="https://www.mdpi.com/2218-1997/10/11/416" /> <rdf:li rdf:resource="https://www.mdpi.com/2218-1997/10/11/415" /> <rdf:li rdf:resource="https://www.mdpi.com/2218-1997/10/11/414" /> <rdf:li rdf:resource="https://www.mdpi.com/2218-1997/10/11/413" /> <rdf:li rdf:resource="https://www.mdpi.com/2218-1997/10/11/412" /> <rdf:li rdf:resource="https://www.mdpi.com/2218-1997/10/11/411" /> <rdf:li rdf:resource="https://www.mdpi.com/2218-1997/10/11/410" /> <rdf:li rdf:resource="https://www.mdpi.com/2218-1997/10/11/409" /> <rdf:li rdf:resource="https://www.mdpi.com/2218-1997/10/11/408" /> <rdf:li rdf:resource="https://www.mdpi.com/2218-1997/10/11/407" /> <rdf:li rdf:resource="https://www.mdpi.com/2218-1997/10/11/406" /> <rdf:li rdf:resource="https://www.mdpi.com/2218-1997/10/11/405" /> <rdf:li rdf:resource="https://www.mdpi.com/2218-1997/10/11/404" /> <rdf:li rdf:resource="https://www.mdpi.com/2218-1997/10/10/403" /> <rdf:li rdf:resource="https://www.mdpi.com/2218-1997/10/10/402" /> <rdf:li rdf:resource="https://www.mdpi.com/2218-1997/10/10/401" /> <rdf:li rdf:resource="https://www.mdpi.com/2218-1997/10/10/400" /> <rdf:li rdf:resource="https://www.mdpi.com/2218-1997/10/10/399" /> <rdf:li rdf:resource="https://www.mdpi.com/2218-1997/10/10/398" /> <rdf:li rdf:resource="https://www.mdpi.com/2218-1997/10/10/397" /> <rdf:li rdf:resource="https://www.mdpi.com/2218-1997/10/10/396" /> <rdf:li rdf:resource="https://www.mdpi.com/2218-1997/10/10/395" /> <rdf:li rdf:resource="https://www.mdpi.com/2218-1997/10/10/394" /> <rdf:li rdf:resource="https://www.mdpi.com/2218-1997/10/10/393" /> <rdf:li rdf:resource="https://www.mdpi.com/2218-1997/10/10/392" /> <rdf:li rdf:resource="https://www.mdpi.com/2218-1997/10/10/391" /> <rdf:li rdf:resource="https://www.mdpi.com/2218-1997/10/10/390" /> <rdf:li rdf:resource="https://www.mdpi.com/2218-1997/10/10/389" /> <rdf:li rdf:resource="https://www.mdpi.com/2218-1997/10/10/388" /> <rdf:li rdf:resource="https://www.mdpi.com/2218-1997/10/10/387" /> <rdf:li rdf:resource="https://www.mdpi.com/2218-1997/10/10/386" /> <rdf:li rdf:resource="https://www.mdpi.com/2218-1997/10/10/385" /> <rdf:li rdf:resource="https://www.mdpi.com/2218-1997/10/10/384" /> <rdf:li rdf:resource="https://www.mdpi.com/2218-1997/10/10/383" /> <rdf:li rdf:resource="https://www.mdpi.com/2218-1997/10/10/382" /> <rdf:li rdf:resource="https://www.mdpi.com/2218-1997/10/10/381" /> <rdf:li rdf:resource="https://www.mdpi.com/2218-1997/10/10/380" /> <rdf:li rdf:resource="https://www.mdpi.com/2218-1997/10/9/379" /> <rdf:li rdf:resource="https://www.mdpi.com/2218-1997/10/9/378" /> <rdf:li rdf:resource="https://www.mdpi.com/2218-1997/10/9/377" /> <rdf:li rdf:resource="https://www.mdpi.com/2218-1997/10/9/376" /> <rdf:li rdf:resource="https://www.mdpi.com/2218-1997/10/9/375" /> <rdf:li rdf:resource="https://www.mdpi.com/2218-1997/10/9/374" /> <rdf:li rdf:resource="https://www.mdpi.com/2218-1997/10/9/373" /> <rdf:li rdf:resource="https://www.mdpi.com/2218-1997/10/9/372" /> <rdf:li rdf:resource="https://www.mdpi.com/2218-1997/10/9/371" /> <rdf:li rdf:resource="https://www.mdpi.com/2218-1997/10/9/370" /> <rdf:li rdf:resource="https://www.mdpi.com/2218-1997/10/9/369" /> <rdf:li rdf:resource="https://www.mdpi.com/2218-1997/10/9/368" /> <rdf:li rdf:resource="https://www.mdpi.com/2218-1997/10/9/367" /> <rdf:li rdf:resource="https://www.mdpi.com/2218-1997/10/9/366" /> <rdf:li rdf:resource="https://www.mdpi.com/2218-1997/10/9/365" /> <rdf:li rdf:resource="https://www.mdpi.com/2218-1997/10/9/364" /> <rdf:li rdf:resource="https://www.mdpi.com/2218-1997/10/9/363" /> <rdf:li rdf:resource="https://www.mdpi.com/2218-1997/10/9/362" /> <rdf:li rdf:resource="https://www.mdpi.com/2218-1997/10/9/361" /> <rdf:li rdf:resource="https://www.mdpi.com/2218-1997/10/9/360" /> <rdf:li rdf:resource="https://www.mdpi.com/2218-1997/10/9/359" /> <rdf:li rdf:resource="https://www.mdpi.com/2218-1997/10/9/358" /> <rdf:li rdf:resource="https://www.mdpi.com/2218-1997/10/9/357" /> <rdf:li rdf:resource="https://www.mdpi.com/2218-1997/10/9/356" /> <rdf:li rdf:resource="https://www.mdpi.com/2218-1997/10/9/355" /> <rdf:li rdf:resource="https://www.mdpi.com/2218-1997/10/9/354" /> <rdf:li rdf:resource="https://www.mdpi.com/2218-1997/10/9/353" /> <rdf:li rdf:resource="https://www.mdpi.com/2218-1997/10/9/352" /> <rdf:li rdf:resource="https://www.mdpi.com/2218-1997/10/9/351" /> <rdf:li rdf:resource="https://www.mdpi.com/2218-1997/10/9/350" /> <rdf:li rdf:resource="https://www.mdpi.com/2218-1997/10/9/349" /> <rdf:li rdf:resource="https://www.mdpi.com/2218-1997/10/9/348" /> <rdf:li rdf:resource="https://www.mdpi.com/2218-1997/10/9/347" /> <rdf:li rdf:resource="https://www.mdpi.com/2218-1997/10/9/346" /> <rdf:li rdf:resource="https://www.mdpi.com/2218-1997/10/9/345" /> <rdf:li rdf:resource="https://www.mdpi.com/2218-1997/10/9/344" /> <rdf:li rdf:resource="https://www.mdpi.com/2218-1997/10/9/343" /> <rdf:li rdf:resource="https://www.mdpi.com/2218-1997/10/9/342" /> <rdf:li rdf:resource="https://www.mdpi.com/2218-1997/10/9/341" /> <rdf:li rdf:resource="https://www.mdpi.com/2218-1997/10/9/340" /> <rdf:li rdf:resource="https://www.mdpi.com/2218-1997/10/9/339" /> <rdf:li rdf:resource="https://www.mdpi.com/2218-1997/10/9/338" /> <rdf:li rdf:resource="https://www.mdpi.com/2218-1997/10/9/337" /> </rdf:Seq> </items> <cc:license rdf:resource="https://creativecommons.org/licenses/by/4.0/" /> </channel> <item rdf:about="https://www.mdpi.com/2218-1997/10/12/436"> <title>Universe, Vol. 10, Pages 436: On the Hypothesis of Exact Conservation of Charged Weak Hadronic Vector Current in the Standard Model</title> <link>https://www.mdpi.com/2218-1997/10/12/436</link> <description>We investigate the reliability of the conservation of the vector current (CVC) hypothesis in the neutron beta decay (n&amp;nbsp;&amp;beta;&amp;minus; decay). We calculate the contribution of the phenomenological term, responsible for the CVC in the hadronic current of the n&amp;nbsp;&amp;beta;&amp;minus; decay (or the CVC effect), to the neutron lifetime. We show that the CVC effect increases the neutron lifetime with a relative contribution of 8.684&amp;times;10&amp;minus;2. This leads to the increase of the neutron lifetime by 76.4 s with respect to the world averaged value &amp;tau;n=880.2(1.0)s from the Particle Data Group. We show that since in the Standard Model there are no interactions that are able to cancel such a huge increase in the neutron lifetime, we have to turn to the interactions beyond the Standard Model, the contribution of which to the neutron lifetime reduces to the Fierz interference term bF only. Cancelling the CVC effect at the level of the experimental accuracy, we obtain bF=0.1219(12). If this value cannot be accepted for the Fierz interference term, the CVC effect induces irresistible problems for description and understanding of the n&amp;nbsp;&amp;beta;&amp;minus; decay.</description> <pubDate>2024-11-22</pubDate> <content:encoded><![CDATA[ Universe, Vol. 10, Pages 436: On the Hypothesis of Exact Conservation of Charged Weak Hadronic Vector Current in the Standard Model Universe <a href="https://www.mdpi.com/2218-1997/10/12/436">doi: 10.3390/universe10120436</a> Authors: Derar Altarawneh Roman H枚llwieser Markus Wellenzohn We investigate the reliability of the conservation of the vector current (CVC) hypothesis in the neutron beta decay (n&amp;nbsp;&amp;beta;&amp;minus; decay). We calculate the contribution of the phenomenological term, responsible for the CVC in the hadronic current of the n&amp;nbsp;&amp;beta;&amp;minus; decay (or the CVC effect), to the neutron lifetime. We show that the CVC effect increases the neutron lifetime with a relative contribution of 8.684&amp;times;10&amp;minus;2. This leads to the increase of the neutron lifetime by 76.4 s with respect to the world averaged value &amp;tau;n=880.2(1.0)s from the Particle Data Group. We show that since in the Standard Model there are no interactions that are able to cancel such a huge increase in the neutron lifetime, we have to turn to the interactions beyond the Standard Model, the contribution of which to the neutron lifetime reduces to the Fierz interference term bF only. Cancelling the CVC effect at the level of the experimental accuracy, we obtain bF=0.1219(12). If this value cannot be accepted for the Fierz interference term, the CVC effect induces irresistible problems for description and understanding of the n&amp;nbsp;&amp;beta;&amp;minus; decay. ]]></content:encoded> <dc:title>On the Hypothesis of Exact Conservation of Charged Weak Hadronic Vector Current in the Standard Model</dc:title> <dc:creator>Derar Altarawneh</dc:creator> <dc:creator>Roman H枚llwieser</dc:creator> <dc:creator>Markus Wellenzohn</dc:creator> <dc:identifier>doi: 10.3390/universe10120436</dc:identifier> <dc:source>Universe</dc:source> <dc:date>2024-11-22</dc:date> <prism:publicationName>Universe</prism:publicationName> <prism:publicationDate>2024-11-22</prism:publicationDate> <prism:volume>10</prism:volume> <prism:number>12</prism:number> <prism:section>Article</prism:section> <prism:startingPage>436</prism:startingPage> <prism:doi>10.3390/universe10120436</prism:doi> <prism:url>https://www.mdpi.com/2218-1997/10/12/436</prism:url> <cc:license rdf:resource="CC BY 4.0"/> </item> <item rdf:about="https://www.mdpi.com/2218-1997/10/12/435"> <title>Universe, Vol. 10, Pages 435: On the Viscous Ringed Disk Evolution in the Kerr Black Hole Spacetime</title> <link>https://www.mdpi.com/2218-1997/10/12/435</link> <description>Supermassive black holes (SMBHs) are observed in active galactic nuclei interacting with their environments, where chaotical, discontinuous accretion episodes may leave matter remnants orbiting the central attractor in the form of sequences of orbiting toroidal structures, with strongly different features as different rotation orientations with respect to the central Kerr BH. Such ringed structures can be characterized by peculiar internal dynamics, where co-rotating and counter-rotating accretion stages can be mixed and distinguished by tori interaction, drying&amp;ndash;feeding processes, screening effects, and inter-disk jet emission. A ringed accretion disk (RAD) is a full general relativistic model of a cluster of toroidal disks, an aggregate of axi-symmetric co-rotating and counter-rotating disks orbiting in the equatorial plane of a single central Kerr SMBH. In this work, we discuss the time evolution of a ringed disk. Our analysis is a detailed numerical study of the evolving RAD properties formed by relativistic thin disks, using a thin disk model and solving a diffusion-like evolution equation for an RAD in the Kerr spacetime, adopting an initial wavy (ringed) density profile. The RAD reaches a single-disk phase, building accretion to the inner edge regulated by the inner edge boundary conditions. The mass flux, the radial drift, and the disk mass of the ringed disk are evaluated and compared to each of its disk components. During early inter-disk interaction, the ring components spread, destroying the internal ringed structure and quickly forming a single disk with timescales governed by ring viscosity prescriptions. Different viscosities and boundary conditions have been tested. We propose that a system of viscously spreading accretion rings can originate as a product of tidal disruption of a multiple stellar system that comes too close to an SMBH.</description> <pubDate>2024-11-22</pubDate> <content:encoded><![CDATA[ Universe, Vol. 10, Pages 435: On the Viscous Ringed Disk Evolution in the Kerr Black Hole Spacetime Universe <a href="https://www.mdpi.com/2218-1997/10/12/435">doi: 10.3390/universe10120435</a> Authors: Daniela Pugliese Zdenek Stuchl铆k Vladimir Karas Supermassive black holes (SMBHs) are observed in active galactic nuclei interacting with their environments, where chaotical, discontinuous accretion episodes may leave matter remnants orbiting the central attractor in the form of sequences of orbiting toroidal structures, with strongly different features as different rotation orientations with respect to the central Kerr BH. Such ringed structures can be characterized by peculiar internal dynamics, where co-rotating and counter-rotating accretion stages can be mixed and distinguished by tori interaction, drying&amp;ndash;feeding processes, screening effects, and inter-disk jet emission. A ringed accretion disk (RAD) is a full general relativistic model of a cluster of toroidal disks, an aggregate of axi-symmetric co-rotating and counter-rotating disks orbiting in the equatorial plane of a single central Kerr SMBH. In this work, we discuss the time evolution of a ringed disk. Our analysis is a detailed numerical study of the evolving RAD properties formed by relativistic thin disks, using a thin disk model and solving a diffusion-like evolution equation for an RAD in the Kerr spacetime, adopting an initial wavy (ringed) density profile. The RAD reaches a single-disk phase, building accretion to the inner edge regulated by the inner edge boundary conditions. The mass flux, the radial drift, and the disk mass of the ringed disk are evaluated and compared to each of its disk components. During early inter-disk interaction, the ring components spread, destroying the internal ringed structure and quickly forming a single disk with timescales governed by ring viscosity prescriptions. Different viscosities and boundary conditions have been tested. We propose that a system of viscously spreading accretion rings can originate as a product of tidal disruption of a multiple stellar system that comes too close to an SMBH. ]]></content:encoded> <dc:title>On the Viscous Ringed Disk Evolution in the Kerr Black Hole Spacetime</dc:title> <dc:creator>Daniela Pugliese</dc:creator> <dc:creator>Zdenek Stuchl铆k</dc:creator> <dc:creator>Vladimir Karas</dc:creator> <dc:identifier>doi: 10.3390/universe10120435</dc:identifier> <dc:source>Universe</dc:source> <dc:date>2024-11-22</dc:date> <prism:publicationName>Universe</prism:publicationName> <prism:publicationDate>2024-11-22</prism:publicationDate> <prism:volume>10</prism:volume> <prism:number>12</prism:number> <prism:section>Article</prism:section> <prism:startingPage>435</prism:startingPage> <prism:doi>10.3390/universe10120435</prism:doi> <prism:url>https://www.mdpi.com/2218-1997/10/12/435</prism:url> <cc:license rdf:resource="CC BY 4.0"/> </item> <item rdf:about="https://www.mdpi.com/2218-1997/10/12/434"> <title>Universe, Vol. 10, Pages 434: Studying Intra-Night Optical Variability of AGNs Using the TESS Survey Data</title> <link>https://www.mdpi.com/2218-1997/10/12/434</link> <description>Active galactic nuclei (AGNs) exhibit significant luminosity variations across the entire electromagnetic spectrum, with timescales ranging from hours to years. Studying the optical variability of AGNs provides crucial insights into their physical properties. In this study, we explore the intra-night optical variability (INOV) of AGNs using data from the TESS satellite&amp;rsquo;s all-sky survey. We derive differential light curves for a sample of 56 AGNs from 30-min cadence TESS full-frame images. Our analysis confirms that BL Lac objects typically exhibit stronger INOV compared to quasars, which generally show weaker variability. The duty cycle for INOV with an amplitude greater than 3% is approximately 4&amp;plusmn;0.7% for quasars and 22&amp;plusmn;5% for BL Lac objects. For INOV with an amplitude exceeding 10%, the corresponding duty cycle decreases to about 0.5&amp;plusmn;0.3% and 5&amp;plusmn;2%, respectively. Furthermore, we identify a potential linear-log relationship between the duty cycle and the INOV amplitude, based on results from this study and previous findings, particularly from the ARIES program.</description> <pubDate>2024-11-21</pubDate> <content:encoded><![CDATA[ Universe, Vol. 10, Pages 434: Studying Intra-Night Optical Variability of AGNs Using the TESS Survey Data Universe <a href="https://www.mdpi.com/2218-1997/10/12/434">doi: 10.3390/universe10120434</a> Authors: Yujian Yang Bo Ma Chen Chen Active galactic nuclei (AGNs) exhibit significant luminosity variations across the entire electromagnetic spectrum, with timescales ranging from hours to years. Studying the optical variability of AGNs provides crucial insights into their physical properties. In this study, we explore the intra-night optical variability (INOV) of AGNs using data from the TESS satellite&amp;rsquo;s all-sky survey. We derive differential light curves for a sample of 56 AGNs from 30-min cadence TESS full-frame images. Our analysis confirms that BL Lac objects typically exhibit stronger INOV compared to quasars, which generally show weaker variability. The duty cycle for INOV with an amplitude greater than 3% is approximately 4&amp;plusmn;0.7% for quasars and 22&amp;plusmn;5% for BL Lac objects. For INOV with an amplitude exceeding 10%, the corresponding duty cycle decreases to about 0.5&amp;plusmn;0.3% and 5&amp;plusmn;2%, respectively. Furthermore, we identify a potential linear-log relationship between the duty cycle and the INOV amplitude, based on results from this study and previous findings, particularly from the ARIES program. ]]></content:encoded> <dc:title>Studying Intra-Night Optical Variability of AGNs Using the TESS Survey Data</dc:title> <dc:creator>Yujian Yang</dc:creator> <dc:creator>Bo Ma</dc:creator> <dc:creator>Chen Chen</dc:creator> <dc:identifier>doi: 10.3390/universe10120434</dc:identifier> <dc:source>Universe</dc:source> <dc:date>2024-11-21</dc:date> <prism:publicationName>Universe</prism:publicationName> <prism:publicationDate>2024-11-21</prism:publicationDate> <prism:volume>10</prism:volume> <prism:number>12</prism:number> <prism:section>Article</prism:section> <prism:startingPage>434</prism:startingPage> <prism:doi>10.3390/universe10120434</prism:doi> <prism:url>https://www.mdpi.com/2218-1997/10/12/434</prism:url> <cc:license rdf:resource="CC BY 4.0"/> </item> <item rdf:about="https://www.mdpi.com/2218-1997/10/11/433"> <title>Universe, Vol. 10, Pages 433: Black Hole Solutions in Non-Minimally Coupled Weyl Connection Gravity</title> <link>https://www.mdpi.com/2218-1997/10/11/433</link> <description>Schwarzschild and Reissner&amp;ndash;Nordstr&amp;oslash;m black hole solutions are found in the context of a non-minimal matter&amp;ndash;curvature coupling with Weyl connection both in vacuum and in the presence of a cosmological constant-like matter content. This model has the advantage of an extra force term which can mimic dark matter and dark energy, and simultaneously following Weyl&amp;rsquo;s idea of unifying gravity and electromagnetism. In fact, vacuum Schwarzschild solutions differ from the ones in a constant curvature scenario in f(R) theories, with the appearance of a coefficient in the term that is linear in r and a corrected &amp;ldquo;cosmological constant&amp;rdquo;. Non-vacuum Schwarzschild solutions formally have the same solutions as in the previous case, with the exception being the physical interpretation of a cosmological constant as the source of the matter Lagrangian and not a simple reparameterization of the f(R) description. Reissner&amp;ndash;Nordstr&amp;oslash;m solutions cannot be found in a vacuum, only in the presence of matter fields, with the result that the solutions also differ from the constant curvature scenario in f(R) theories by the term being linear in r, the corrected/dressed charge, and the cosmological constant. These results have bearings on future numerical simulations for black holes and gravitational waves in next-generation wavelet templates.</description> <pubDate>2024-11-20</pubDate> <content:encoded><![CDATA[ Universe, Vol. 10, Pages 433: Black Hole Solutions in Non-Minimally Coupled Weyl Connection Gravity Universe <a href="https://www.mdpi.com/2218-1997/10/11/433">doi: 10.3390/universe10110433</a> Authors: Maria Margarida Lima Cl谩udio Gomes Schwarzschild and Reissner&amp;ndash;Nordstr&amp;oslash;m black hole solutions are found in the context of a non-minimal matter&amp;ndash;curvature coupling with Weyl connection both in vacuum and in the presence of a cosmological constant-like matter content. This model has the advantage of an extra force term which can mimic dark matter and dark energy, and simultaneously following Weyl&amp;rsquo;s idea of unifying gravity and electromagnetism. In fact, vacuum Schwarzschild solutions differ from the ones in a constant curvature scenario in f(R) theories, with the appearance of a coefficient in the term that is linear in r and a corrected &amp;ldquo;cosmological constant&amp;rdquo;. Non-vacuum Schwarzschild solutions formally have the same solutions as in the previous case, with the exception being the physical interpretation of a cosmological constant as the source of the matter Lagrangian and not a simple reparameterization of the f(R) description. Reissner&amp;ndash;Nordstr&amp;oslash;m solutions cannot be found in a vacuum, only in the presence of matter fields, with the result that the solutions also differ from the constant curvature scenario in f(R) theories by the term being linear in r, the corrected/dressed charge, and the cosmological constant. These results have bearings on future numerical simulations for black holes and gravitational waves in next-generation wavelet templates. ]]></content:encoded> <dc:title>Black Hole Solutions in Non-Minimally Coupled Weyl Connection Gravity</dc:title> <dc:creator>Maria Margarida Lima</dc:creator> <dc:creator>Cl谩udio Gomes</dc:creator> <dc:identifier>doi: 10.3390/universe10110433</dc:identifier> <dc:source>Universe</dc:source> <dc:date>2024-11-20</dc:date> <prism:publicationName>Universe</prism:publicationName> <prism:publicationDate>2024-11-20</prism:publicationDate> <prism:volume>10</prism:volume> <prism:number>11</prism:number> <prism:section>Article</prism:section> <prism:startingPage>433</prism:startingPage> <prism:doi>10.3390/universe10110433</prism:doi> <prism:url>https://www.mdpi.com/2218-1997/10/11/433</prism:url> <cc:license rdf:resource="CC BY 4.0"/> </item> <item rdf:about="https://www.mdpi.com/2218-1997/10/11/432"> <title>Universe, Vol. 10, Pages 432: The Properties of an Edge-On Low Surface Brightness Galaxies Sample</title> <link>https://www.mdpi.com/2218-1997/10/11/432</link> <description>We analyzed the properties of a sample of edge-on low-surface brightness galaxies, which are referred to as Cao23 ELSBGs. Cao23 ELSBGs exhibit a wide range of luminosities (&amp;minus;22 &amp;lt; Mr &amp;lt; &amp;minus;13) with a mean scale length of 3.19 &amp;plusmn; 1.48 kpc. Compared to HI-rich dwarf ELSBGs, Cao23 ELSBGs display more extended disk structures and redder (g-r) colors. They are also, on average, more massive than HI-rich dwarf ELSBGs. Star formation rates (SFRs) were calculated using WISE 12 &amp;mu;m luminosity conversions and spectral energy distribution (SED) fitting methods, respectively. Cao23 ELSBGs fall below the main sequence with specific star formation rates (sSFRs) primarily in the range of 0.01&amp;ndash;0.1 Gyr&amp;minus;1. More massive Cao23 LSBGs tend to have lower sSFRs. Additionally, we derived the non-parametric star formation histories (SFHs) of Cao23 ELSBGs by SED fitting, dividing the SFHs into seven look back time bins with constant SFRs assumed for each bin. Our analysis indicates that high-mass (M&amp;lowast; &amp;gt; 109.0M&amp;#8857;) Cao23 ELSBGs assembled their mass earlier than their lower-mass counterparts, supporting a downsizing trend for LSBGs.</description> <pubDate>2024-11-20</pubDate> <content:encoded><![CDATA[ Universe, Vol. 10, Pages 432: The Properties of an Edge-On Low Surface Brightness Galaxies Sample Universe <a href="https://www.mdpi.com/2218-1997/10/11/432">doi: 10.3390/universe10110432</a> Authors: Tian-Wen Cao Zi-Jian Li Pei-Bin Chen Venu M. Kalari Cheng Cheng Gaspar Galaz Hong Wu Junfeng Wang We analyzed the properties of a sample of edge-on low-surface brightness galaxies, which are referred to as Cao23 ELSBGs. Cao23 ELSBGs exhibit a wide range of luminosities (&amp;minus;22 &amp;lt; Mr &amp;lt; &amp;minus;13) with a mean scale length of 3.19 &amp;plusmn; 1.48 kpc. Compared to HI-rich dwarf ELSBGs, Cao23 ELSBGs display more extended disk structures and redder (g-r) colors. They are also, on average, more massive than HI-rich dwarf ELSBGs. Star formation rates (SFRs) were calculated using WISE 12 &amp;mu;m luminosity conversions and spectral energy distribution (SED) fitting methods, respectively. Cao23 ELSBGs fall below the main sequence with specific star formation rates (sSFRs) primarily in the range of 0.01&amp;ndash;0.1 Gyr&amp;minus;1. More massive Cao23 LSBGs tend to have lower sSFRs. Additionally, we derived the non-parametric star formation histories (SFHs) of Cao23 ELSBGs by SED fitting, dividing the SFHs into seven look back time bins with constant SFRs assumed for each bin. Our analysis indicates that high-mass (M&amp;lowast; &amp;gt; 109.0M&amp;#8857;) Cao23 ELSBGs assembled their mass earlier than their lower-mass counterparts, supporting a downsizing trend for LSBGs. ]]></content:encoded> <dc:title>The Properties of an Edge-On Low Surface Brightness Galaxies Sample</dc:title> <dc:creator>Tian-Wen Cao</dc:creator> <dc:creator>Zi-Jian Li</dc:creator> <dc:creator>Pei-Bin Chen</dc:creator> <dc:creator>Venu M. Kalari</dc:creator> <dc:creator>Cheng Cheng</dc:creator> <dc:creator>Gaspar Galaz</dc:creator> <dc:creator>Hong Wu</dc:creator> <dc:creator>Junfeng Wang</dc:creator> <dc:identifier>doi: 10.3390/universe10110432</dc:identifier> <dc:source>Universe</dc:source> <dc:date>2024-11-20</dc:date> <prism:publicationName>Universe</prism:publicationName> <prism:publicationDate>2024-11-20</prism:publicationDate> <prism:volume>10</prism:volume> <prism:number>11</prism:number> <prism:section>Article</prism:section> <prism:startingPage>432</prism:startingPage> <prism:doi>10.3390/universe10110432</prism:doi> <prism:url>https://www.mdpi.com/2218-1997/10/11/432</prism:url> <cc:license rdf:resource="CC BY 4.0"/> </item> <item rdf:about="https://www.mdpi.com/2218-1997/10/11/431"> <title>Universe, Vol. 10, Pages 431: The Composite Spectral Energy Distribution of Quasars Is Surprisingly Universal Since Cosmic Noon</title> <link>https://www.mdpi.com/2218-1997/10/11/431</link> <description>Leveraging the photometric data of the Sloan Digital Sky Survey and the Galaxy Evolution Explorer (GALEX), we construct mean/median spectral energy distributions (SEDs) for unique bright quasars in redshift bins of 0.2 and up to z&amp;#8771;3, after taking the GALEX non-detection into account. Further correcting for the absorption of the intergalactic medium, these mean/median quasar SEDs constitute a surprisingly redshift-independent mean/median composite SED from the rest-frame optical down to &amp;#8771;500&amp;nbsp;A&amp;#730; for quasars with bolometric luminosity brighter than 1045.5ergs&amp;minus;1. Moreover, the mean/median composite quasar SED is plausibly also independent of black hole mass and Eddington ratio, and suggests similar properties of dust and gas in the quasar host galaxies since cosmic noon. Both the mean and median composite SEDs are nicely consistent with previous mean composite quasar spectra at wavelengths beyond &amp;#8771;1000&amp;nbsp;A&amp;#730;, but at shorter wavelengths, are redder, indicating, on average, less ionizing radiation than previously expected. Through comparing the model-predicted to the observed composite quasar SEDs, we favor a simply truncated disk model, rather than a standard thin disk model, for the quasar central engine, though we request more sophisticated disk models. Future deep ultraviolet facilities, such as the China Space Station Telescope and the Ultraviolet Explorer, would prompt revolutions in many aspects, including the quasar central engine, production of the broad emission lines in quasars, and cosmic reionization.</description> <pubDate>2024-11-19</pubDate> <content:encoded><![CDATA[ Universe, Vol. 10, Pages 431: The Composite Spectral Energy Distribution of Quasars Is Surprisingly Universal Since Cosmic Noon Universe <a href="https://www.mdpi.com/2218-1997/10/11/431">doi: 10.3390/universe10110431</a> Authors: Zhenyi Cai Leveraging the photometric data of the Sloan Digital Sky Survey and the Galaxy Evolution Explorer (GALEX), we construct mean/median spectral energy distributions (SEDs) for unique bright quasars in redshift bins of 0.2 and up to z&amp;#8771;3, after taking the GALEX non-detection into account. Further correcting for the absorption of the intergalactic medium, these mean/median quasar SEDs constitute a surprisingly redshift-independent mean/median composite SED from the rest-frame optical down to &amp;#8771;500&amp;nbsp;A&amp;#730; for quasars with bolometric luminosity brighter than 1045.5ergs&amp;minus;1. Moreover, the mean/median composite quasar SED is plausibly also independent of black hole mass and Eddington ratio, and suggests similar properties of dust and gas in the quasar host galaxies since cosmic noon. Both the mean and median composite SEDs are nicely consistent with previous mean composite quasar spectra at wavelengths beyond &amp;#8771;1000&amp;nbsp;A&amp;#730;, but at shorter wavelengths, are redder, indicating, on average, less ionizing radiation than previously expected. Through comparing the model-predicted to the observed composite quasar SEDs, we favor a simply truncated disk model, rather than a standard thin disk model, for the quasar central engine, though we request more sophisticated disk models. Future deep ultraviolet facilities, such as the China Space Station Telescope and the Ultraviolet Explorer, would prompt revolutions in many aspects, including the quasar central engine, production of the broad emission lines in quasars, and cosmic reionization. ]]></content:encoded> <dc:title>The Composite Spectral Energy Distribution of Quasars Is Surprisingly Universal Since Cosmic Noon</dc:title> <dc:creator>Zhenyi Cai</dc:creator> <dc:identifier>doi: 10.3390/universe10110431</dc:identifier> <dc:source>Universe</dc:source> <dc:date>2024-11-19</dc:date> <prism:publicationName>Universe</prism:publicationName> <prism:publicationDate>2024-11-19</prism:publicationDate> <prism:volume>10</prism:volume> <prism:number>11</prism:number> <prism:section>Article</prism:section> <prism:startingPage>431</prism:startingPage> <prism:doi>10.3390/universe10110431</prism:doi> <prism:url>https://www.mdpi.com/2218-1997/10/11/431</prism:url> <cc:license rdf:resource="CC BY 4.0"/> </item> <item rdf:about="https://www.mdpi.com/2218-1997/10/11/430"> <title>Universe, Vol. 10, Pages 430: Black Holes with a Cloud of Strings and Quintessence in a Non-Linear Electrodynamics Scenario</title> <link>https://www.mdpi.com/2218-1997/10/11/430</link> <description>We obtain exact black hole solutions to Einstein gravity coupled with a nonlinear electrodynamics field, in the presence of a cloud of strings and quintessence, as sources. The solutions have four parameters, namely m, k, a, and &amp;alpha;, corresponding to the physical mass of the black hole, the nonlinear charge of a self-gravitating magnetic field, the cloud of strings, and the intensity of the quintessential fluid. The consequences of these sources on the regularity or singularity of the solutions, on their horizons, as well as on the energy conditions, are discussed. We study some aspects concerning the thermodynamics of the black hole, by taking into account the mass, Hawking temperature, and heat capacity and show how these quantities depend on the presence of the cloud of strings and quintessence, in the scenario considered.</description> <pubDate>2024-11-19</pubDate> <content:encoded><![CDATA[ Universe, Vol. 10, Pages 430: Black Holes with a Cloud of Strings and Quintessence in a Non-Linear Electrodynamics Scenario Universe <a href="https://www.mdpi.com/2218-1997/10/11/430">doi: 10.3390/universe10110430</a> Authors: Francinaldo Florencio do Nascimento Valdir Barbosa Bezerra Jefferson de Morais Toledo We obtain exact black hole solutions to Einstein gravity coupled with a nonlinear electrodynamics field, in the presence of a cloud of strings and quintessence, as sources. The solutions have four parameters, namely m, k, a, and &amp;alpha;, corresponding to the physical mass of the black hole, the nonlinear charge of a self-gravitating magnetic field, the cloud of strings, and the intensity of the quintessential fluid. The consequences of these sources on the regularity or singularity of the solutions, on their horizons, as well as on the energy conditions, are discussed. We study some aspects concerning the thermodynamics of the black hole, by taking into account the mass, Hawking temperature, and heat capacity and show how these quantities depend on the presence of the cloud of strings and quintessence, in the scenario considered. ]]></content:encoded> <dc:title>Black Holes with a Cloud of Strings and Quintessence in a Non-Linear Electrodynamics Scenario</dc:title> <dc:creator>Francinaldo Florencio do Nascimento</dc:creator> <dc:creator>Valdir Barbosa Bezerra</dc:creator> <dc:creator>Jefferson de Morais Toledo</dc:creator> <dc:identifier>doi: 10.3390/universe10110430</dc:identifier> <dc:source>Universe</dc:source> <dc:date>2024-11-19</dc:date> <prism:publicationName>Universe</prism:publicationName> <prism:publicationDate>2024-11-19</prism:publicationDate> <prism:volume>10</prism:volume> <prism:number>11</prism:number> <prism:section>Article</prism:section> <prism:startingPage>430</prism:startingPage> <prism:doi>10.3390/universe10110430</prism:doi> <prism:url>https://www.mdpi.com/2218-1997/10/11/430</prism:url> <cc:license rdf:resource="CC BY 4.0"/> </item> <item rdf:about="https://www.mdpi.com/2218-1997/10/11/429"> <title>Universe, Vol. 10, Pages 429: Cosmological Models in Lovelock Gravity: An Overview of Recent Progress</title> <link>https://www.mdpi.com/2218-1997/10/11/429</link> <description>In the current review, we provide a summary of the recent progress made in the cosmological aspect of extra-dimensional Lovelock gravity. Our review covers a wide variety of particular model/matter source combinations: Einstein&amp;ndash;Gauss&amp;ndash;Bonnet as well as cubic Lovelock gravities with vacuum, cosmological constant, perfect fluid, spatial curvature, and some of their combinations. Our analysis suggests that it is possible to set constraints on the parameters of the above-mentioned models from the simple requirement of the existence of a smooth transition from the initial singularity to a realistic low-energy regime. Initially, anisotropic space naturally evolves into a configuration with two isotropic subspaces, and if one of these subspaces is three-dimensional and is expanding while another is contracting, we call it realistic compactification. Of course, the process is not devoid of obstacles, and in our paper, we review the results of the compactification occurrence investigation for the above-mentioned models. In particular, for vacuum and &amp;Lambda;-term EGB models, compactification is not suppressed (but is not the only possible outcome either) if the number of extra dimensions is D&amp;#10878;2; for vacuum cubic Lovelock gravities it is always present (however, cubic Lovelock gravity is defined only for D&amp;#10878;3 number of extra dimensions); for the EGB model with perfect fluid it is present for D=2 (we have not considered this model in higher dimensions yet), and in the presence of spatial curvature, the realistic stabilization of extra dimensions is always present (however, such a model is well-defined only in D&amp;#10878;4 number of extra dimensions).</description> <pubDate>2024-11-18</pubDate> <content:encoded><![CDATA[ Universe, Vol. 10, Pages 429: Cosmological Models in Lovelock Gravity: An Overview of Recent Progress Universe <a href="https://www.mdpi.com/2218-1997/10/11/429">doi: 10.3390/universe10110429</a> Authors: Sergey Pavluchenko In the current review, we provide a summary of the recent progress made in the cosmological aspect of extra-dimensional Lovelock gravity. Our review covers a wide variety of particular model/matter source combinations: Einstein&amp;ndash;Gauss&amp;ndash;Bonnet as well as cubic Lovelock gravities with vacuum, cosmological constant, perfect fluid, spatial curvature, and some of their combinations. Our analysis suggests that it is possible to set constraints on the parameters of the above-mentioned models from the simple requirement of the existence of a smooth transition from the initial singularity to a realistic low-energy regime. Initially, anisotropic space naturally evolves into a configuration with two isotropic subspaces, and if one of these subspaces is three-dimensional and is expanding while another is contracting, we call it realistic compactification. Of course, the process is not devoid of obstacles, and in our paper, we review the results of the compactification occurrence investigation for the above-mentioned models. In particular, for vacuum and &amp;Lambda;-term EGB models, compactification is not suppressed (but is not the only possible outcome either) if the number of extra dimensions is D&amp;#10878;2; for vacuum cubic Lovelock gravities it is always present (however, cubic Lovelock gravity is defined only for D&amp;#10878;3 number of extra dimensions); for the EGB model with perfect fluid it is present for D=2 (we have not considered this model in higher dimensions yet), and in the presence of spatial curvature, the realistic stabilization of extra dimensions is always present (however, such a model is well-defined only in D&amp;#10878;4 number of extra dimensions). ]]></content:encoded> <dc:title>Cosmological Models in Lovelock Gravity: An Overview of Recent Progress</dc:title> <dc:creator>Sergey Pavluchenko</dc:creator> <dc:identifier>doi: 10.3390/universe10110429</dc:identifier> <dc:source>Universe</dc:source> <dc:date>2024-11-18</dc:date> <prism:publicationName>Universe</prism:publicationName> <prism:publicationDate>2024-11-18</prism:publicationDate> <prism:volume>10</prism:volume> <prism:number>11</prism:number> <prism:section>Review</prism:section> <prism:startingPage>429</prism:startingPage> <prism:doi>10.3390/universe10110429</prism:doi> <prism:url>https://www.mdpi.com/2218-1997/10/11/429</prism:url> <cc:license rdf:resource="CC BY 4.0"/> </item> <item rdf:about="https://www.mdpi.com/2218-1997/10/11/428"> <title>Universe, Vol. 10, Pages 428: Current Density Induced by a Cosmic String in de Sitter Spacetime in the Presence of Two Flat Boundaries</title> <link>https://www.mdpi.com/2218-1997/10/11/428</link> <description>In this paper, we investigate the vacuum bosonic current density induced by a carrying-magnetic-flux cosmic string in a (D+1)-de Sitter spacetime considering the presence of two flat boundaries perpendicular to it. In this setup, the Robin boundary conditions are imposed on the scalar charged quantum field on the boundaries. The particular cases of Dirichlet and Neumann boundary conditions are studied separately. Due to the coupling of the quantum scalar field with the classical gauge field, corresponding to a magnetic flux running along the string&amp;rsquo;s core, a nonzero vacuum expectation value for the current density operator along the azimuthal direction is induced. The two boundaries divide the space in three regions with different properties of the vacuum states. In this way, our main objective is to calculate the induced currents in these three regions. In order to develop this analysis we calculate, for both regions, the positive frequency Wightman functions. Because the vacuum bosonic current in dS space has been investigated before, in this paper we consider only the contributions induced by the boundaries. We show that for each region the azimuthal current densities are odd functions of the magnetic flux along the string. To probe the correctness of our results, we take the particular cases and analyze some asymptotic limits of the parameters of the model. Also some graphs are presented exhibiting the behavior of the current with relevant physical parameter of the system.</description> <pubDate>2024-11-17</pubDate> <content:encoded><![CDATA[ Universe, Vol. 10, Pages 428: Current Density Induced by a Cosmic String in de Sitter Spacetime in the Presence of Two Flat Boundaries Universe <a href="https://www.mdpi.com/2218-1997/10/11/428">doi: 10.3390/universe10110428</a> Authors: Wagner Oliveira dos Santos Herondy F. Santana Mota Eug锚nio R. Bezerra de Mello In this paper, we investigate the vacuum bosonic current density induced by a carrying-magnetic-flux cosmic string in a (D+1)-de Sitter spacetime considering the presence of two flat boundaries perpendicular to it. In this setup, the Robin boundary conditions are imposed on the scalar charged quantum field on the boundaries. The particular cases of Dirichlet and Neumann boundary conditions are studied separately. Due to the coupling of the quantum scalar field with the classical gauge field, corresponding to a magnetic flux running along the string&amp;rsquo;s core, a nonzero vacuum expectation value for the current density operator along the azimuthal direction is induced. The two boundaries divide the space in three regions with different properties of the vacuum states. In this way, our main objective is to calculate the induced currents in these three regions. In order to develop this analysis we calculate, for both regions, the positive frequency Wightman functions. Because the vacuum bosonic current in dS space has been investigated before, in this paper we consider only the contributions induced by the boundaries. We show that for each region the azimuthal current densities are odd functions of the magnetic flux along the string. To probe the correctness of our results, we take the particular cases and analyze some asymptotic limits of the parameters of the model. Also some graphs are presented exhibiting the behavior of the current with relevant physical parameter of the system. ]]></content:encoded> <dc:title>Current Density Induced by a Cosmic String in de Sitter Spacetime in the Presence of Two Flat Boundaries</dc:title> <dc:creator>Wagner Oliveira dos Santos</dc:creator> <dc:creator>Herondy F. Santana Mota</dc:creator> <dc:creator>Eug锚nio R. Bezerra de Mello</dc:creator> <dc:identifier>doi: 10.3390/universe10110428</dc:identifier> <dc:source>Universe</dc:source> <dc:date>2024-11-17</dc:date> <prism:publicationName>Universe</prism:publicationName> <prism:publicationDate>2024-11-17</prism:publicationDate> <prism:volume>10</prism:volume> <prism:number>11</prism:number> <prism:section>Article</prism:section> <prism:startingPage>428</prism:startingPage> <prism:doi>10.3390/universe10110428</prism:doi> <prism:url>https://www.mdpi.com/2218-1997/10/11/428</prism:url> <cc:license rdf:resource="CC BY 4.0"/> </item> <item rdf:about="https://www.mdpi.com/2218-1997/10/11/427"> <title>Universe, Vol. 10, Pages 427: Post-Newtonian Effects in Compact Binaries with a Dark Matter Spike: A Lagrangian Approach</title> <link>https://www.mdpi.com/2218-1997/10/11/427</link> <description>We apply the Lagrangian method to study the post-Newtonian evolution of a compact binary system with environmental effects, including a dark matter spike, and obtain the resulting gravitational wave emission. This formalism allows one to incorporate post-Newtonian effects up to any desired known order, as well as any other environmental effect around the binary, as long as their dissipation power or force formulae are known. In particular, in this work, we employ this method to study a black hole&amp;ndash;black hole binary system of mass ratio 105 by including post-Newtonian effects of order 1PN and 2.5PN, as well as the effect of relativistic dynamical friction. We obtain the modified orbits and the corresponding modified gravitational waveform. Finally, we contrast these modifications against the LISA sensitivity curve in frequency space and show that this observatory can detect the associated signals.</description> <pubDate>2024-11-17</pubDate> <content:encoded><![CDATA[ Universe, Vol. 10, Pages 427: Post-Newtonian Effects in Compact Binaries with a Dark Matter Spike: A Lagrangian Approach Universe <a href="https://www.mdpi.com/2218-1997/10/11/427">doi: 10.3390/universe10110427</a> Authors: Diego Montalvo Adam Smith-Orlik Saeed Rastgoo Laura Sagunski Niklas Becker Hazkeel Khan We apply the Lagrangian method to study the post-Newtonian evolution of a compact binary system with environmental effects, including a dark matter spike, and obtain the resulting gravitational wave emission. This formalism allows one to incorporate post-Newtonian effects up to any desired known order, as well as any other environmental effect around the binary, as long as their dissipation power or force formulae are known. In particular, in this work, we employ this method to study a black hole&amp;ndash;black hole binary system of mass ratio 105 by including post-Newtonian effects of order 1PN and 2.5PN, as well as the effect of relativistic dynamical friction. We obtain the modified orbits and the corresponding modified gravitational waveform. Finally, we contrast these modifications against the LISA sensitivity curve in frequency space and show that this observatory can detect the associated signals. ]]></content:encoded> <dc:title>Post-Newtonian Effects in Compact Binaries with a Dark Matter Spike: A Lagrangian Approach</dc:title> <dc:creator>Diego Montalvo</dc:creator> <dc:creator>Adam Smith-Orlik</dc:creator> <dc:creator>Saeed Rastgoo</dc:creator> <dc:creator>Laura Sagunski</dc:creator> <dc:creator>Niklas Becker</dc:creator> <dc:creator>Hazkeel Khan</dc:creator> <dc:identifier>doi: 10.3390/universe10110427</dc:identifier> <dc:source>Universe</dc:source> <dc:date>2024-11-17</dc:date> <prism:publicationName>Universe</prism:publicationName> <prism:publicationDate>2024-11-17</prism:publicationDate> <prism:volume>10</prism:volume> <prism:number>11</prism:number> <prism:section>Article</prism:section> <prism:startingPage>427</prism:startingPage> <prism:doi>10.3390/universe10110427</prism:doi> <prism:url>https://www.mdpi.com/2218-1997/10/11/427</prism:url> <cc:license rdf:resource="CC BY 4.0"/> </item> <item rdf:about="https://www.mdpi.com/2218-1997/10/11/426"> <title>Universe, Vol. 10, Pages 426: Probing the Dark Universe with Gravitational Waves</title> <link>https://www.mdpi.com/2218-1997/10/11/426</link> <description>Gravitational waves (GWs) are expected to interact with dark energy and dark matter, affecting their propagation on cosmological scales. To model this interaction, we derive a gauge-invariant effective equation and action valid for all GW polarizations. This is achieved by encoding the effects of GW interactions at different orders of perturbation into a polarization-, frequency-, and time-dependent effective speed. The invariance of perturbations under time-dependent conformal transformations and the gauge invariance of GWs allow us to derive the unitary gauge effective action in any conformally related frame, thereby clarifying the relationship between the Einstein and Jordan frames. Tests of the polarization and frequency dependencies in the propagation time and luminosity distance of different GW polarizations allow us to probe the dark Universe, which acts as an effective medium, modeled by the GW effective speed.</description> <pubDate>2024-11-15</pubDate> <content:encoded><![CDATA[ Universe, Vol. 10, Pages 426: Probing the Dark Universe with Gravitational Waves Universe <a href="https://www.mdpi.com/2218-1997/10/11/426">doi: 10.3390/universe10110426</a> Authors: Antonio Enea Romano Gravitational waves (GWs) are expected to interact with dark energy and dark matter, affecting their propagation on cosmological scales. To model this interaction, we derive a gauge-invariant effective equation and action valid for all GW polarizations. This is achieved by encoding the effects of GW interactions at different orders of perturbation into a polarization-, frequency-, and time-dependent effective speed. The invariance of perturbations under time-dependent conformal transformations and the gauge invariance of GWs allow us to derive the unitary gauge effective action in any conformally related frame, thereby clarifying the relationship between the Einstein and Jordan frames. Tests of the polarization and frequency dependencies in the propagation time and luminosity distance of different GW polarizations allow us to probe the dark Universe, which acts as an effective medium, modeled by the GW effective speed. ]]></content:encoded> <dc:title>Probing the Dark Universe with Gravitational Waves</dc:title> <dc:creator>Antonio Enea Romano</dc:creator> <dc:identifier>doi: 10.3390/universe10110426</dc:identifier> <dc:source>Universe</dc:source> <dc:date>2024-11-15</dc:date> <prism:publicationName>Universe</prism:publicationName> <prism:publicationDate>2024-11-15</prism:publicationDate> <prism:volume>10</prism:volume> <prism:number>11</prism:number> <prism:section>Article</prism:section> <prism:startingPage>426</prism:startingPage> <prism:doi>10.3390/universe10110426</prism:doi> <prism:url>https://www.mdpi.com/2218-1997/10/11/426</prism:url> <cc:license rdf:resource="CC BY 4.0"/> </item> <item rdf:about="https://www.mdpi.com/2218-1997/10/11/425"> <title>Universe, Vol. 10, Pages 425: Editorial to the Special Issue &ldquo;Space Missions to Small Bodies: Results and Future Activities&rdquo;</title> <link>https://www.mdpi.com/2218-1997/10/11/425</link> <description>Small bodies (asteroids, comets, and satellites) are the most primitive bodies of our solar system and, for this reason, represent the key to understanding its origin and early evolution [...]</description> <pubDate>2024-11-14</pubDate> <content:encoded><![CDATA[ Universe, Vol. 10, Pages 425: Editorial to the Special Issue &ldquo;Space Missions to Small Bodies: Results and Future Activities&rdquo; Universe <a href="https://www.mdpi.com/2218-1997/10/11/425">doi: 10.3390/universe10110425</a> Authors: Andrea Longobardo Small bodies (asteroids, comets, and satellites) are the most primitive bodies of our solar system and, for this reason, represent the key to understanding its origin and early evolution [...] ]]></content:encoded> <dc:title>Editorial to the Special Issue &amp;ldquo;Space Missions to Small Bodies: Results and Future Activities&amp;rdquo;</dc:title> <dc:creator>Andrea Longobardo</dc:creator> <dc:identifier>doi: 10.3390/universe10110425</dc:identifier> <dc:source>Universe</dc:source> <dc:date>2024-11-14</dc:date> <prism:publicationName>Universe</prism:publicationName> <prism:publicationDate>2024-11-14</prism:publicationDate> <prism:volume>10</prism:volume> <prism:number>11</prism:number> <prism:section>Editorial</prism:section> <prism:startingPage>425</prism:startingPage> <prism:doi>10.3390/universe10110425</prism:doi> <prism:url>https://www.mdpi.com/2218-1997/10/11/425</prism:url> <cc:license rdf:resource="CC BY 4.0"/> </item> <item rdf:about="https://www.mdpi.com/2218-1997/10/11/424"> <title>Universe, Vol. 10, Pages 424: Sources and Radiations of the Fermi Bubbles</title> <link>https://www.mdpi.com/2218-1997/10/11/424</link> <description>Two enigmatic gamma-ray features in the galactic central region, known as Fermi Bubbles (FBs), were found from Fermi-LAT data. An energy release, (e.g., by tidal disruption events in the Galactic Center, GC), generates a cavity with a shock that expands into the local ambient medium of the galactic halo. A decade or so ago, a phenomenological model of the FBs was suggested as a result of routine star disruptions by the supermassive black hole in the GC which might provide enough energy for large-scale structures, like the FBs. In 2020, analytical and numerical models of the FBs as a process of routine tidal disruption of stars near the GC were developed; these disruption events can provide enough cumulative energy to form and maintain large-scale structures like the FBs. The disruption events are expected to be 10&amp;minus;4&amp;sim;10&amp;minus;5yr&amp;minus;1, providing an average power of energy release from the GC into the halo of E&amp;#729;&amp;sim;3&amp;times;1041 erg s&amp;minus;1, which is needed to support the FBs. Analysis of the evolution of superbubbles in exponentially stratified disks concluded that the FB envelope would be destroyed by the Rayleigh&amp;ndash;Taylor (RT) instabilities at late stages. The shell is composed of swept-up gas of the bubble, whose thickness is much thinner in comparison to the size of the envelope. We assume that hydrodynamic turbulence is excited in the FB envelope by the RT instability. In this case, the universal energy spectrum of turbulence may be developed in the inertial range of wavenumbers of fluctuations (the Kolmogorov&amp;ndash;Obukhov spectrum). From our model we suppose the power of the FBs is transformed partly into the energy of hydrodynamic turbulence in the envelope. If so, hydrodynamic turbulence may generate MHD fluctuations, which accelerate cosmic rays there and generate gamma-ray and radio emission from the FBs. We hope that this model may interpret the observed nonthermal emission from the bubbles.</description> <pubDate>2024-11-12</pubDate> <content:encoded><![CDATA[ Universe, Vol. 10, Pages 424: Sources and Radiations of the Fermi Bubbles Universe <a href="https://www.mdpi.com/2218-1997/10/11/424">doi: 10.3390/universe10110424</a> Authors: Vladimir A. Dogiel Chung-Ming Ko Two enigmatic gamma-ray features in the galactic central region, known as Fermi Bubbles (FBs), were found from Fermi-LAT data. An energy release, (e.g., by tidal disruption events in the Galactic Center, GC), generates a cavity with a shock that expands into the local ambient medium of the galactic halo. A decade or so ago, a phenomenological model of the FBs was suggested as a result of routine star disruptions by the supermassive black hole in the GC which might provide enough energy for large-scale structures, like the FBs. In 2020, analytical and numerical models of the FBs as a process of routine tidal disruption of stars near the GC were developed; these disruption events can provide enough cumulative energy to form and maintain large-scale structures like the FBs. The disruption events are expected to be 10&amp;minus;4&amp;sim;10&amp;minus;5yr&amp;minus;1, providing an average power of energy release from the GC into the halo of E&amp;#729;&amp;sim;3&amp;times;1041 erg s&amp;minus;1, which is needed to support the FBs. Analysis of the evolution of superbubbles in exponentially stratified disks concluded that the FB envelope would be destroyed by the Rayleigh&amp;ndash;Taylor (RT) instabilities at late stages. The shell is composed of swept-up gas of the bubble, whose thickness is much thinner in comparison to the size of the envelope. We assume that hydrodynamic turbulence is excited in the FB envelope by the RT instability. In this case, the universal energy spectrum of turbulence may be developed in the inertial range of wavenumbers of fluctuations (the Kolmogorov&amp;ndash;Obukhov spectrum). From our model we suppose the power of the FBs is transformed partly into the energy of hydrodynamic turbulence in the envelope. If so, hydrodynamic turbulence may generate MHD fluctuations, which accelerate cosmic rays there and generate gamma-ray and radio emission from the FBs. We hope that this model may interpret the observed nonthermal emission from the bubbles. ]]></content:encoded> <dc:title>Sources and Radiations of the Fermi Bubbles</dc:title> <dc:creator>Vladimir A. Dogiel</dc:creator> <dc:creator>Chung-Ming Ko</dc:creator> <dc:identifier>doi: 10.3390/universe10110424</dc:identifier> <dc:source>Universe</dc:source> <dc:date>2024-11-12</dc:date> <prism:publicationName>Universe</prism:publicationName> <prism:publicationDate>2024-11-12</prism:publicationDate> <prism:volume>10</prism:volume> <prism:number>11</prism:number> <prism:section>Article</prism:section> <prism:startingPage>424</prism:startingPage> <prism:doi>10.3390/universe10110424</prism:doi> <prism:url>https://www.mdpi.com/2218-1997/10/11/424</prism:url> <cc:license rdf:resource="CC BY 4.0"/> </item> <item rdf:about="https://www.mdpi.com/2218-1997/10/11/423"> <title>Universe, Vol. 10, Pages 423: Exploring &gamma;-Ray Flares from High-Redshift Blazar B3 1343+451 at GeV Energies</title> <link>https://www.mdpi.com/2218-1997/10/11/423</link> <description>We study the temporal and spectral variability properties of the high-redshift blazar B3 1343+451 utilizing Fermi-LAT data from 2008 to 2022 in the energy range of 0.1&amp;ndash;300 GeV. We identify six major flares with many substructures and analyze their temporal and spectral properties in detail. The fastest rise and decay timescales are found to be 4.8 &amp;plusmn; 0.48 h and 5.28 &amp;plusmn; 0.72 h, respectively. The size of the emission region is constrained to be R &amp;sim; 5.18 &amp;times; 1015&amp;ndash;1.56 &amp;times; 1016 cm with the typical Doppler factors of &amp;delta; &amp;sim; 10&amp;ndash;30. Most of the peaks from the flares exhibit a symmetric temporal profile within the error bars, implying that the rise and decay timescales are dominated by the disturbances caused by dense plasma blobs passing through the standing shock front in the jet region. We also find that four flares are better fitted with a log-parabolic distribution, while two flares are better fitted with a power-law distribution. Our results indicate that the emission regions vary from one flare to another, which is consistent with earlier results.</description> <pubDate>2024-11-11</pubDate> <content:encoded><![CDATA[ Universe, Vol. 10, Pages 423: Exploring &gamma;-Ray Flares from High-Redshift Blazar B3 1343+451 at GeV Energies Universe <a href="https://www.mdpi.com/2218-1997/10/11/423">doi: 10.3390/universe10110423</a> Authors: Xiongfei Geng Yang Liu Gang Cao Jing Fan Xiongbang Yang Nan Ding Minghu Gao Yehui Yang Zhijie Zhang We study the temporal and spectral variability properties of the high-redshift blazar B3 1343+451 utilizing Fermi-LAT data from 2008 to 2022 in the energy range of 0.1&amp;ndash;300 GeV. We identify six major flares with many substructures and analyze their temporal and spectral properties in detail. The fastest rise and decay timescales are found to be 4.8 &amp;plusmn; 0.48 h and 5.28 &amp;plusmn; 0.72 h, respectively. The size of the emission region is constrained to be R &amp;sim; 5.18 &amp;times; 1015&amp;ndash;1.56 &amp;times; 1016 cm with the typical Doppler factors of &amp;delta; &amp;sim; 10&amp;ndash;30. Most of the peaks from the flares exhibit a symmetric temporal profile within the error bars, implying that the rise and decay timescales are dominated by the disturbances caused by dense plasma blobs passing through the standing shock front in the jet region. We also find that four flares are better fitted with a log-parabolic distribution, while two flares are better fitted with a power-law distribution. Our results indicate that the emission regions vary from one flare to another, which is consistent with earlier results. ]]></content:encoded> <dc:title>Exploring &amp;gamma;-Ray Flares from High-Redshift Blazar B3 1343+451 at GeV Energies</dc:title> <dc:creator>Xiongfei Geng</dc:creator> <dc:creator>Yang Liu</dc:creator> <dc:creator>Gang Cao</dc:creator> <dc:creator>Jing Fan</dc:creator> <dc:creator>Xiongbang Yang</dc:creator> <dc:creator>Nan Ding</dc:creator> <dc:creator>Minghu Gao</dc:creator> <dc:creator>Yehui Yang</dc:creator> <dc:creator>Zhijie Zhang</dc:creator> <dc:identifier>doi: 10.3390/universe10110423</dc:identifier> <dc:source>Universe</dc:source> <dc:date>2024-11-11</dc:date> <prism:publicationName>Universe</prism:publicationName> <prism:publicationDate>2024-11-11</prism:publicationDate> <prism:volume>10</prism:volume> <prism:number>11</prism:number> <prism:section>Article</prism:section> <prism:startingPage>423</prism:startingPage> <prism:doi>10.3390/universe10110423</prism:doi> <prism:url>https://www.mdpi.com/2218-1997/10/11/423</prism:url> <cc:license rdf:resource="CC BY 4.0"/> </item> <item rdf:about="https://www.mdpi.com/2218-1997/10/11/422"> <title>Universe, Vol. 10, Pages 422: Solar Radio Emissions</title> <link>https://www.mdpi.com/2218-1997/10/11/422</link> <description>The radio emission from the Sun covers a very wide frequency band ranging from several hundreds of GHz (sub-millimeter wavelength) down to sub-MHz (kilometer wavelength) [...]</description> <pubDate>2024-11-09</pubDate> <content:encoded><![CDATA[ Universe, Vol. 10, Pages 422: Solar Radio Emissions Universe <a href="https://www.mdpi.com/2218-1997/10/11/422">doi: 10.3390/universe10110422</a> Authors: Baolin Tan Jing Huang The radio emission from the Sun covers a very wide frequency band ranging from several hundreds of GHz (sub-millimeter wavelength) down to sub-MHz (kilometer wavelength) [...] ]]></content:encoded> <dc:title>Solar Radio Emissions</dc:title> <dc:creator>Baolin Tan</dc:creator> <dc:creator>Jing Huang</dc:creator> <dc:identifier>doi: 10.3390/universe10110422</dc:identifier> <dc:source>Universe</dc:source> <dc:date>2024-11-09</dc:date> <prism:publicationName>Universe</prism:publicationName> <prism:publicationDate>2024-11-09</prism:publicationDate> <prism:volume>10</prism:volume> <prism:number>11</prism:number> <prism:section>Editorial</prism:section> <prism:startingPage>422</prism:startingPage> <prism:doi>10.3390/universe10110422</prism:doi> <prism:url>https://www.mdpi.com/2218-1997/10/11/422</prism:url> <cc:license rdf:resource="CC BY 4.0"/> </item> <item rdf:about="https://www.mdpi.com/2218-1997/10/11/421"> <title>Universe, Vol. 10, Pages 421: Gravitational Lensing Effects from Models of Loop Quantum Gravity with Rigorous Quantum Parameters</title> <link>https://www.mdpi.com/2218-1997/10/11/421</link> <description>Many previous works have studied gravitational lensing effects from Loop Quantum Gravity. So far, gravitational lensing effects from Loop Quantum Gravity have only been studied by choosing large quantum parameters much larger than the Planck scale. However, by construction, the quantum parameters of the effective models of Loop Quantum Gravity are usually related to the Planck length and, thus, are extremely small. In this work, by strictly imposing the quantum parameters as initially constructed, we study the true quantum corrections of gravitational lensing effects by five effective black hole models of Loop Quantum Gravity. Our study reveals several interesting results, including the different scales of quantum corrections displayed by each model and the connection between the quantum correction of deflection angles and the quantum correction of the metric. Observables related to the gravitational lensing effect are also obtained for all models in the case of SgrA* and M87*.</description> <pubDate>2024-11-08</pubDate> <content:encoded><![CDATA[ Universe, Vol. 10, Pages 421: Gravitational Lensing Effects from Models of Loop Quantum Gravity with Rigorous Quantum Parameters Universe <a href="https://www.mdpi.com/2218-1997/10/11/421">doi: 10.3390/universe10110421</a> Authors: Haida Li Xiangdong Zhang Many previous works have studied gravitational lensing effects from Loop Quantum Gravity. So far, gravitational lensing effects from Loop Quantum Gravity have only been studied by choosing large quantum parameters much larger than the Planck scale. However, by construction, the quantum parameters of the effective models of Loop Quantum Gravity are usually related to the Planck length and, thus, are extremely small. In this work, by strictly imposing the quantum parameters as initially constructed, we study the true quantum corrections of gravitational lensing effects by five effective black hole models of Loop Quantum Gravity. Our study reveals several interesting results, including the different scales of quantum corrections displayed by each model and the connection between the quantum correction of deflection angles and the quantum correction of the metric. Observables related to the gravitational lensing effect are also obtained for all models in the case of SgrA* and M87*. ]]></content:encoded> <dc:title>Gravitational Lensing Effects from Models of Loop Quantum Gravity with Rigorous Quantum Parameters</dc:title> <dc:creator>Haida Li</dc:creator> <dc:creator>Xiangdong Zhang</dc:creator> <dc:identifier>doi: 10.3390/universe10110421</dc:identifier> <dc:source>Universe</dc:source> <dc:date>2024-11-08</dc:date> <prism:publicationName>Universe</prism:publicationName> <prism:publicationDate>2024-11-08</prism:publicationDate> <prism:volume>10</prism:volume> <prism:number>11</prism:number> <prism:section>Article</prism:section> <prism:startingPage>421</prism:startingPage> <prism:doi>10.3390/universe10110421</prism:doi> <prism:url>https://www.mdpi.com/2218-1997/10/11/421</prism:url> <cc:license rdf:resource="CC BY 4.0"/> </item> <item rdf:about="https://www.mdpi.com/2218-1997/10/11/419"> <title>Universe, Vol. 10, Pages 419: Semi-Symmetric Metric Gravity: A Brief Overview</title> <link>https://www.mdpi.com/2218-1997/10/11/419</link> <description>We present a review of the Semi-Symmetric Metric Gravity (SSMG) theory, representing a geometric extension of standard general relativity, based on a connection introduced by Friedmann and Schouten in 1924. The semi-symmetric connection is a connection that generalizes the Levi-Civita one by allowing for the presence of a simple form of the torsion, described in terms of a torsion vector. The Einstein field equations are postulated to have the same form as in standard general relativity, thus relating the Einstein tensor constructed with the help of the semi-symmetric connection, with the energy&amp;ndash;momentum tensor tensor. The inclusion of the torsion contributions in the field equations has intriguing cosmological implications, particularly during the late-time evolution of the Universe. Presumably, these effects also dominate under high-energy conditions, and thus SSMG could potentially address unresolved issues in general relativity and cosmology, such as the initial singularity, inflation, or the 7Li problem of the Big-Bang Nucleosynthesis. The explicit presence of torsion in the field equations leads to the non-conservation of the energy&amp;ndash;momentum tensor tensor, which can be interpreted within the irreversible thermodynamics of open systems as describing particle creation processes. We also review in detail the cosmological applications of the theory, and investigate the statistical tests for several models, by constraining the model parameters via comparison with several observational datasets.</description> <pubDate>2024-11-07</pubDate> <content:encoded><![CDATA[ Universe, Vol. 10, Pages 419: Semi-Symmetric Metric Gravity: A Brief Overview Universe <a href="https://www.mdpi.com/2218-1997/10/11/419">doi: 10.3390/universe10110419</a> Authors: Himanshu Chaudhary Lehel Csillag Tiberiu Harko We present a review of the Semi-Symmetric Metric Gravity (SSMG) theory, representing a geometric extension of standard general relativity, based on a connection introduced by Friedmann and Schouten in 1924. The semi-symmetric connection is a connection that generalizes the Levi-Civita one by allowing for the presence of a simple form of the torsion, described in terms of a torsion vector. The Einstein field equations are postulated to have the same form as in standard general relativity, thus relating the Einstein tensor constructed with the help of the semi-symmetric connection, with the energy&amp;ndash;momentum tensor tensor. The inclusion of the torsion contributions in the field equations has intriguing cosmological implications, particularly during the late-time evolution of the Universe. Presumably, these effects also dominate under high-energy conditions, and thus SSMG could potentially address unresolved issues in general relativity and cosmology, such as the initial singularity, inflation, or the 7Li problem of the Big-Bang Nucleosynthesis. The explicit presence of torsion in the field equations leads to the non-conservation of the energy&amp;ndash;momentum tensor tensor, which can be interpreted within the irreversible thermodynamics of open systems as describing particle creation processes. We also review in detail the cosmological applications of the theory, and investigate the statistical tests for several models, by constraining the model parameters via comparison with several observational datasets. ]]></content:encoded> <dc:title>Semi-Symmetric Metric Gravity: A Brief Overview</dc:title> <dc:creator>Himanshu Chaudhary</dc:creator> <dc:creator>Lehel Csillag</dc:creator> <dc:creator>Tiberiu Harko</dc:creator> <dc:identifier>doi: 10.3390/universe10110419</dc:identifier> <dc:source>Universe</dc:source> <dc:date>2024-11-07</dc:date> <prism:publicationName>Universe</prism:publicationName> <prism:publicationDate>2024-11-07</prism:publicationDate> <prism:volume>10</prism:volume> <prism:number>11</prism:number> <prism:section>Review</prism:section> <prism:startingPage>419</prism:startingPage> <prism:doi>10.3390/universe10110419</prism:doi> <prism:url>https://www.mdpi.com/2218-1997/10/11/419</prism:url> <cc:license rdf:resource="CC BY 4.0"/> </item> <item rdf:about="https://www.mdpi.com/2218-1997/10/11/420"> <title>Universe, Vol. 10, Pages 420: Comparing a Gauge-Invariant Formulation and a &ldquo;Conventional Complete Gauge-Fixing Approach&rdquo; for l=0,1-Mode Perturbations on the Schwarzschild Background Spacetime</title> <link>https://www.mdpi.com/2218-1997/10/11/420</link> <description>This article provides a comparison of the gauge-invariant formulation for l=0,1-mode perturbations on the Schwarzschild background spacetime, proposed by the same author in 2021, and a &amp;ldquo;conventional complete gauge-fixing approach&amp;rdquo; where the spherical harmonic functions Ylm as the scalar harmonics are used from the starting point. Although it is often stated that &amp;ldquo;gauge-invariant formulations in general-relativistic perturbations are equivalent to complete gauge-fixing approaches&amp;rdquo;, we conclude that, as a result of this comparison, the derived solutions through the proposed gauge-invariant formulation and those through a &amp;ldquo;conventional complete gauge-fixing approach&amp;rdquo; are different. It is pointed out that there is a case where the boundary conditions and initial conditions are restricted in a conventional complete gauge-fixing approach.</description> <pubDate>2024-11-07</pubDate> <content:encoded><![CDATA[ Universe, Vol. 10, Pages 420: Comparing a Gauge-Invariant Formulation and a &ldquo;Conventional Complete Gauge-Fixing Approach&rdquo; for l=0,1-Mode Perturbations on the Schwarzschild Background Spacetime Universe <a href="https://www.mdpi.com/2218-1997/10/11/420">doi: 10.3390/universe10110420</a> Authors: Kouji Nakamura This article provides a comparison of the gauge-invariant formulation for l=0,1-mode perturbations on the Schwarzschild background spacetime, proposed by the same author in 2021, and a &amp;ldquo;conventional complete gauge-fixing approach&amp;rdquo; where the spherical harmonic functions Ylm as the scalar harmonics are used from the starting point. Although it is often stated that &amp;ldquo;gauge-invariant formulations in general-relativistic perturbations are equivalent to complete gauge-fixing approaches&amp;rdquo;, we conclude that, as a result of this comparison, the derived solutions through the proposed gauge-invariant formulation and those through a &amp;ldquo;conventional complete gauge-fixing approach&amp;rdquo; are different. It is pointed out that there is a case where the boundary conditions and initial conditions are restricted in a conventional complete gauge-fixing approach. ]]></content:encoded> <dc:title>Comparing a Gauge-Invariant Formulation and a &amp;ldquo;Conventional Complete Gauge-Fixing Approach&amp;rdquo; for l=0,1-Mode Perturbations on the Schwarzschild Background Spacetime</dc:title> <dc:creator>Kouji Nakamura</dc:creator> <dc:identifier>doi: 10.3390/universe10110420</dc:identifier> <dc:source>Universe</dc:source> <dc:date>2024-11-07</dc:date> <prism:publicationName>Universe</prism:publicationName> <prism:publicationDate>2024-11-07</prism:publicationDate> <prism:volume>10</prism:volume> <prism:number>11</prism:number> <prism:section>Article</prism:section> <prism:startingPage>420</prism:startingPage> <prism:doi>10.3390/universe10110420</prism:doi> <prism:url>https://www.mdpi.com/2218-1997/10/11/420</prism:url> <cc:license rdf:resource="CC BY 4.0"/> </item> <item rdf:about="https://www.mdpi.com/2218-1997/10/11/418"> <title>Universe, Vol. 10, Pages 418: Foundational Issues in Dynamical Casimir Effect and Analogue Features in Cosmological Particle Creation</title> <link>https://www.mdpi.com/2218-1997/10/11/418</link> <description>Moving mirrors as analogue sources of Hawking radiation from black holes have been explored extensively but less so with cosmological particle creation (CPC), even though the analogy between the dynamical Casimir effect (DCE) and CPC based on the mechanism of the parametric amplification of quantum field fluctuations has also been known for a long time. This &amp;lsquo;perspective&amp;rsquo; essay intends to convey some of the rigor and thoroughness of quantum field theory in curved spacetime, which serves as the theoretical foundation of CPC, to DCE, which enjoys a variety of active experimental explorations. We have selected seven issues of relevance to address, starting from the naively simple ones, e.g., why one should be bothered with &amp;lsquo;curved&amp;rsquo; spacetime when performing a laboratory experiment in ostensibly flat space, to foundational theoretical ones, such as the frequent appearance of nonlocal dissipation in the system dynamics induced by colored noises in its field environment, the existence of quantum Lenz law and fluctuation&amp;ndash;dissipation relations in the backreaction effects of DCE emission on the moving atom/mirror or the source, and the construction of a microphysics model to account for the dynamical responses of a mirror or medium. The strengthening of the theoretical ground for DCE is not only useful for improving conceptual clarity but needed for the development of the proof-of-concept type of future experimental designs for DCE. The results from the DCE experiments in turn will enrich our understanding of quantum field effects in the early universe because they are, in the spirit of analogue gravity, our best hopes for the verification of these fundamental processes.</description> <pubDate>2024-11-07</pubDate> <content:encoded><![CDATA[ Universe, Vol. 10, Pages 418: Foundational Issues in Dynamical Casimir Effect and Analogue Features in Cosmological Particle Creation Universe <a href="https://www.mdpi.com/2218-1997/10/11/418">doi: 10.3390/universe10110418</a> Authors: Jen-Tsung Hsiang Bei-Lok Hu Moving mirrors as analogue sources of Hawking radiation from black holes have been explored extensively but less so with cosmological particle creation (CPC), even though the analogy between the dynamical Casimir effect (DCE) and CPC based on the mechanism of the parametric amplification of quantum field fluctuations has also been known for a long time. This &amp;lsquo;perspective&amp;rsquo; essay intends to convey some of the rigor and thoroughness of quantum field theory in curved spacetime, which serves as the theoretical foundation of CPC, to DCE, which enjoys a variety of active experimental explorations. We have selected seven issues of relevance to address, starting from the naively simple ones, e.g., why one should be bothered with &amp;lsquo;curved&amp;rsquo; spacetime when performing a laboratory experiment in ostensibly flat space, to foundational theoretical ones, such as the frequent appearance of nonlocal dissipation in the system dynamics induced by colored noises in its field environment, the existence of quantum Lenz law and fluctuation&amp;ndash;dissipation relations in the backreaction effects of DCE emission on the moving atom/mirror or the source, and the construction of a microphysics model to account for the dynamical responses of a mirror or medium. The strengthening of the theoretical ground for DCE is not only useful for improving conceptual clarity but needed for the development of the proof-of-concept type of future experimental designs for DCE. The results from the DCE experiments in turn will enrich our understanding of quantum field effects in the early universe because they are, in the spirit of analogue gravity, our best hopes for the verification of these fundamental processes. ]]></content:encoded> <dc:title>Foundational Issues in Dynamical Casimir Effect and Analogue Features in Cosmological Particle Creation</dc:title> <dc:creator>Jen-Tsung Hsiang</dc:creator> <dc:creator>Bei-Lok Hu</dc:creator> <dc:identifier>doi: 10.3390/universe10110418</dc:identifier> <dc:source>Universe</dc:source> <dc:date>2024-11-07</dc:date> <prism:publicationName>Universe</prism:publicationName> <prism:publicationDate>2024-11-07</prism:publicationDate> <prism:volume>10</prism:volume> <prism:number>11</prism:number> <prism:section>Perspective</prism:section> <prism:startingPage>418</prism:startingPage> <prism:doi>10.3390/universe10110418</prism:doi> <prism:url>https://www.mdpi.com/2218-1997/10/11/418</prism:url> <cc:license rdf:resource="CC BY 4.0"/> </item> <item rdf:about="https://www.mdpi.com/2218-1997/10/11/417"> <title>Universe, Vol. 10, Pages 417: Linking Turbulent Interplanetary Magnetic Field Fluctuations and Current Sheets</title> <link>https://www.mdpi.com/2218-1997/10/11/417</link> <description>The study aims to understand the role of solar wind current sheets (CSs) in shaping the spectrum of turbulent fluctuations and driving dissipation processes in space plasma. Local non-adiabatic heating and acceleration of charged particles in the solar wind is one of the most intriguing challenges in space physics. Leading theories attribute these effects to turbulent heating, often associated with magnetic reconnection at small-scale coherent structures in the solar wind, such as CSs and flux ropes. We identify CSs observed at 1 AU in different types of the solar wind around and within an interplanetary coronal mass ejection (ICME) and analyze the corresponding characteristics of the turbulent cascade. It is found that the spectra of fluctuations of the interplanetary magnetic field may be reshaped due to the CS impact potentially leading to local disruptions in energy transfer along the cascade of turbulent fluctuations. Case studies of the spectra behavior at the peak of the CS number show their steepening at MHD scales, flattening at kinetic scales, and merging of the spectra into a single form, with the break almost disappearing. In the broader vicinity of the CS number peak, the behavior of spectral parameters changes sharply, but not always following the same pattern. The statistical analysis shows a clear correlation between the break frequency and the CS number. These results are consistent with the picture of turbulent reconnection at CSs. The CS occurrence is found to be statistically linked with the increased temperature. In the ICME sheath, there are two CS populations observed in the hottest and coldest plasma.</description> <pubDate>2024-11-07</pubDate> <content:encoded><![CDATA[ Universe, Vol. 10, Pages 417: Linking Turbulent Interplanetary Magnetic Field Fluctuations and Current Sheets Universe <a href="https://www.mdpi.com/2218-1997/10/11/417">doi: 10.3390/universe10110417</a> Authors: Maria O. Riazantseva Timofey V. Treves Olga Khabarova Liudmila S. Rakhmanova Yuri I. Yermolaev Alexander A. Khokhlachev The study aims to understand the role of solar wind current sheets (CSs) in shaping the spectrum of turbulent fluctuations and driving dissipation processes in space plasma. Local non-adiabatic heating and acceleration of charged particles in the solar wind is one of the most intriguing challenges in space physics. Leading theories attribute these effects to turbulent heating, often associated with magnetic reconnection at small-scale coherent structures in the solar wind, such as CSs and flux ropes. We identify CSs observed at 1 AU in different types of the solar wind around and within an interplanetary coronal mass ejection (ICME) and analyze the corresponding characteristics of the turbulent cascade. It is found that the spectra of fluctuations of the interplanetary magnetic field may be reshaped due to the CS impact potentially leading to local disruptions in energy transfer along the cascade of turbulent fluctuations. Case studies of the spectra behavior at the peak of the CS number show their steepening at MHD scales, flattening at kinetic scales, and merging of the spectra into a single form, with the break almost disappearing. In the broader vicinity of the CS number peak, the behavior of spectral parameters changes sharply, but not always following the same pattern. The statistical analysis shows a clear correlation between the break frequency and the CS number. These results are consistent with the picture of turbulent reconnection at CSs. The CS occurrence is found to be statistically linked with the increased temperature. In the ICME sheath, there are two CS populations observed in the hottest and coldest plasma. ]]></content:encoded> <dc:title>Linking Turbulent Interplanetary Magnetic Field Fluctuations and Current Sheets</dc:title> <dc:creator>Maria O. Riazantseva</dc:creator> <dc:creator>Timofey V. Treves</dc:creator> <dc:creator>Olga Khabarova</dc:creator> <dc:creator>Liudmila S. Rakhmanova</dc:creator> <dc:creator>Yuri I. Yermolaev</dc:creator> <dc:creator>Alexander A. Khokhlachev</dc:creator> <dc:identifier>doi: 10.3390/universe10110417</dc:identifier> <dc:source>Universe</dc:source> <dc:date>2024-11-07</dc:date> <prism:publicationName>Universe</prism:publicationName> <prism:publicationDate>2024-11-07</prism:publicationDate> <prism:volume>10</prism:volume> <prism:number>11</prism:number> <prism:section>Article</prism:section> <prism:startingPage>417</prism:startingPage> <prism:doi>10.3390/universe10110417</prism:doi> <prism:url>https://www.mdpi.com/2218-1997/10/11/417</prism:url> <cc:license rdf:resource="CC BY 4.0"/> </item> <item rdf:about="https://www.mdpi.com/2218-1997/10/11/416"> <title>Universe, Vol. 10, Pages 416: Profile Variation in PSR B0355+54 over a Narrow Frequency Range</title> <link>https://www.mdpi.com/2218-1997/10/11/416</link> <description>We investigate changes in the shape of the averaged pulse profile in PSR B0355+54 (PSR J0358+5413) based on data obtained at the center frequency of 1250 MHz using the Five-hundred-meter Aperture Spherical radio Telescope (FAST). Our dataset consists of 12 non-consecutive observations, each lasting between 1 and 2 h. Considerable variation is observed in the averaged profiles across the observations even though each is folded from thousands of single pulses. Changes in the profile are measured through the ratio (R) between the peak intensities of the leading and trailing components. We find that the averaged pulse profile exhibits significant variation across observations, but distinctive from typical profile mode-changing. By dividing the frequency bandwidth into eight sub-bands, we demonstrate that the shape of the averaged profile undergoes significant evolution with frequency. In general, the changes in R across the sub-bands are different in different observations, but its value is uniform at low frequencies implying a more consistent emission. We demonstrate that the profile stabilization timescale for this pulsar is much longer than commonly suggested for ordinary pulsars, which is likely due to non-uniform and varying arrangement of the emission sources in the emission region.</description> <pubDate>2024-11-06</pubDate> <content:encoded><![CDATA[ Universe, Vol. 10, Pages 416: Profile Variation in PSR B0355+54 over a Narrow Frequency Range Universe <a href="https://www.mdpi.com/2218-1997/10/11/416">doi: 10.3390/universe10110416</a> Authors: Shibo Jiang Lin Li Rai Yuen Jianping Yuan Jumei Yao Xun Shi Yonghua Xu Jianling Chen Zhigang Wen We investigate changes in the shape of the averaged pulse profile in PSR B0355+54 (PSR J0358+5413) based on data obtained at the center frequency of 1250 MHz using the Five-hundred-meter Aperture Spherical radio Telescope (FAST). Our dataset consists of 12 non-consecutive observations, each lasting between 1 and 2 h. Considerable variation is observed in the averaged profiles across the observations even though each is folded from thousands of single pulses. Changes in the profile are measured through the ratio (R) between the peak intensities of the leading and trailing components. We find that the averaged pulse profile exhibits significant variation across observations, but distinctive from typical profile mode-changing. By dividing the frequency bandwidth into eight sub-bands, we demonstrate that the shape of the averaged profile undergoes significant evolution with frequency. In general, the changes in R across the sub-bands are different in different observations, but its value is uniform at low frequencies implying a more consistent emission. We demonstrate that the profile stabilization timescale for this pulsar is much longer than commonly suggested for ordinary pulsars, which is likely due to non-uniform and varying arrangement of the emission sources in the emission region. ]]></content:encoded> <dc:title>Profile Variation in PSR B0355+54 over a Narrow Frequency Range</dc:title> <dc:creator>Shibo Jiang</dc:creator> <dc:creator>Lin Li</dc:creator> <dc:creator>Rai Yuen</dc:creator> <dc:creator>Jianping Yuan</dc:creator> <dc:creator>Jumei Yao</dc:creator> <dc:creator>Xun Shi</dc:creator> <dc:creator>Yonghua Xu</dc:creator> <dc:creator>Jianling Chen</dc:creator> <dc:creator>Zhigang Wen</dc:creator> <dc:identifier>doi: 10.3390/universe10110416</dc:identifier> <dc:source>Universe</dc:source> <dc:date>2024-11-06</dc:date> <prism:publicationName>Universe</prism:publicationName> <prism:publicationDate>2024-11-06</prism:publicationDate> <prism:volume>10</prism:volume> <prism:number>11</prism:number> <prism:section>Article</prism:section> <prism:startingPage>416</prism:startingPage> <prism:doi>10.3390/universe10110416</prism:doi> <prism:url>https://www.mdpi.com/2218-1997/10/11/416</prism:url> <cc:license rdf:resource="CC BY 4.0"/> </item> <item rdf:about="https://www.mdpi.com/2218-1997/10/11/415"> <title>Universe, Vol. 10, Pages 415: Neutron Beta Decay and Exact Conservation of Charged Weak Hadronic Vector Current in the Standard Model</title> <link>https://www.mdpi.com/2218-1997/10/11/415</link> <description>We investigate the reliability of the hypothesis of exact conservation of the charged weak hadronic vector current in neutron &amp;beta;&amp;minus;-decay with a polarized neutron and an unpolarized proton and electron. We calculate the contributions of the phenomenological term responsible for Exact Conservation of the charged weak hadronic Vector Current (or the ECVC effect) in neutron &amp;beta;&amp;minus;-decay, even for different masses of the neutron and proton, to the correlation coefficients, together with a complete set of contributions of scalar and tensor interactions beyond the Standard Model (SM). We argue that if the total contributions of scalar and tensor interactions beyond the SM fail to reconcile the experimental data on the correlation coefficients with the contributions of the ECVC effect, one may conclude that the charged weak hadronic vector current is not conserved in the hadronic transitions of weak processes with different masses of incoming and outgoing hadrons.</description> <pubDate>2024-11-06</pubDate> <content:encoded><![CDATA[ Universe, Vol. 10, Pages 415: Neutron Beta Decay and Exact Conservation of Charged Weak Hadronic Vector Current in the Standard Model Universe <a href="https://www.mdpi.com/2218-1997/10/11/415">doi: 10.3390/universe10110415</a> Authors: Derar Altarawneh Roman H枚llwieser Markus Wellenzohn We investigate the reliability of the hypothesis of exact conservation of the charged weak hadronic vector current in neutron &amp;beta;&amp;minus;-decay with a polarized neutron and an unpolarized proton and electron. We calculate the contributions of the phenomenological term responsible for Exact Conservation of the charged weak hadronic Vector Current (or the ECVC effect) in neutron &amp;beta;&amp;minus;-decay, even for different masses of the neutron and proton, to the correlation coefficients, together with a complete set of contributions of scalar and tensor interactions beyond the Standard Model (SM). We argue that if the total contributions of scalar and tensor interactions beyond the SM fail to reconcile the experimental data on the correlation coefficients with the contributions of the ECVC effect, one may conclude that the charged weak hadronic vector current is not conserved in the hadronic transitions of weak processes with different masses of incoming and outgoing hadrons. ]]></content:encoded> <dc:title>Neutron Beta Decay and Exact Conservation of Charged Weak Hadronic Vector Current in the Standard Model</dc:title> <dc:creator>Derar Altarawneh</dc:creator> <dc:creator>Roman H枚llwieser</dc:creator> <dc:creator>Markus Wellenzohn</dc:creator> <dc:identifier>doi: 10.3390/universe10110415</dc:identifier> <dc:source>Universe</dc:source> <dc:date>2024-11-06</dc:date> <prism:publicationName>Universe</prism:publicationName> <prism:publicationDate>2024-11-06</prism:publicationDate> <prism:volume>10</prism:volume> <prism:number>11</prism:number> <prism:section>Article</prism:section> <prism:startingPage>415</prism:startingPage> <prism:doi>10.3390/universe10110415</prism:doi> <prism:url>https://www.mdpi.com/2218-1997/10/11/415</prism:url> <cc:license rdf:resource="CC BY 4.0"/> </item> <item rdf:about="https://www.mdpi.com/2218-1997/10/11/414"> <title>Universe, Vol. 10, Pages 414: Estimation of the Chances to Find New Phenomena at the LHC in a Model-Agnostic Combinatorial Analysis</title> <link>https://www.mdpi.com/2218-1997/10/11/414</link> <description>In this paper, we estimate the number of event topologies that have the potential to be produced in pp collisions at the Large Hadron Collider (LHC) without violating kinematic and other constraints. We use numerical calculations and combinatorics, guided by large-scale Monte Carlo simulations of Standard Model (SM) processes. Then, we set the upper limit on the probability that new physics may escape detection, assuming a model-agnostic approach. The calculated probability is unexpectedly large, and the fact that LHC has not found new physics until now is not entirely surprising. Theoretical limitations and experimental challenges in observing new physics within the studied exclusive event classes are examined.</description> <pubDate>2024-11-05</pubDate> <content:encoded><![CDATA[ Universe, Vol. 10, Pages 414: Estimation of the Chances to Find New Phenomena at the LHC in a Model-Agnostic Combinatorial Analysis Universe <a href="https://www.mdpi.com/2218-1997/10/11/414">doi: 10.3390/universe10110414</a> Authors: Sergei V. Chekanov In this paper, we estimate the number of event topologies that have the potential to be produced in pp collisions at the Large Hadron Collider (LHC) without violating kinematic and other constraints. We use numerical calculations and combinatorics, guided by large-scale Monte Carlo simulations of Standard Model (SM) processes. Then, we set the upper limit on the probability that new physics may escape detection, assuming a model-agnostic approach. The calculated probability is unexpectedly large, and the fact that LHC has not found new physics until now is not entirely surprising. Theoretical limitations and experimental challenges in observing new physics within the studied exclusive event classes are examined. ]]></content:encoded> <dc:title>Estimation of the Chances to Find New Phenomena at the LHC in a Model-Agnostic Combinatorial Analysis</dc:title> <dc:creator>Sergei V. Chekanov</dc:creator> <dc:identifier>doi: 10.3390/universe10110414</dc:identifier> <dc:source>Universe</dc:source> <dc:date>2024-11-05</dc:date> <prism:publicationName>Universe</prism:publicationName> <prism:publicationDate>2024-11-05</prism:publicationDate> <prism:volume>10</prism:volume> <prism:number>11</prism:number> <prism:section>Article</prism:section> <prism:startingPage>414</prism:startingPage> <prism:doi>10.3390/universe10110414</prism:doi> <prism:url>https://www.mdpi.com/2218-1997/10/11/414</prism:url> <cc:license rdf:resource="CC BY 4.0"/> </item> <item rdf:about="https://www.mdpi.com/2218-1997/10/11/413"> <title>Universe, Vol. 10, Pages 413: Studying the Properties of Spacetime with an Improved Dynamical Model of the Inner Solar System</title> <link>https://www.mdpi.com/2218-1997/10/11/413</link> <description>Physical properties of the Sun (orientation of rotation axis, oblateness coefficient J2&amp;#8857;, and change rate of the gravitational parameter &amp;mu;&amp;#729;&amp;#8857;) are determined using a dynamical model describing the motion of the Sun, planets, the Moon, asteroids, and Trans-Neptunian objects (TNOs). Among the many kinds of observations used to determine the orbits and physical properties of the bodies, the most important for our study are precise interplanetary ranging data: Earth&amp;ndash;Mercury ranges from MESSENGER spacecraft and Earth&amp;ndash;Mars ranges from Odyssey and MRO. The findings allow us to improve the model of the Sun in modern planetary ephemerides. First, the dynamically determined direction of the Sun&amp;rsquo;s pole is &amp;asymp;2&amp;deg; off the visible axis of rotation of the Sun&amp;rsquo;s surface, which is corroborated by present knowledge of the Sun&amp;rsquo;s interior. Second, the change rate of the Sun&amp;rsquo;s gravitational parameter is found to be smaller (in absolute value) than the nominal value derived from the estimate of mass loss through radiation and solar wind. Possible interpretations are discussed.</description> <pubDate>2024-11-03</pubDate> <content:encoded><![CDATA[ Universe, Vol. 10, Pages 413: Studying the Properties of Spacetime with an Improved Dynamical Model of the Inner Solar System Universe <a href="https://www.mdpi.com/2218-1997/10/11/413">doi: 10.3390/universe10110413</a> Authors: Dmitry Pavlov Ivan Dolgakov Physical properties of the Sun (orientation of rotation axis, oblateness coefficient J2&amp;#8857;, and change rate of the gravitational parameter &amp;mu;&amp;#729;&amp;#8857;) are determined using a dynamical model describing the motion of the Sun, planets, the Moon, asteroids, and Trans-Neptunian objects (TNOs). Among the many kinds of observations used to determine the orbits and physical properties of the bodies, the most important for our study are precise interplanetary ranging data: Earth&amp;ndash;Mercury ranges from MESSENGER spacecraft and Earth&amp;ndash;Mars ranges from Odyssey and MRO. The findings allow us to improve the model of the Sun in modern planetary ephemerides. First, the dynamically determined direction of the Sun&amp;rsquo;s pole is &amp;asymp;2&amp;deg; off the visible axis of rotation of the Sun&amp;rsquo;s surface, which is corroborated by present knowledge of the Sun&amp;rsquo;s interior. Second, the change rate of the Sun&amp;rsquo;s gravitational parameter is found to be smaller (in absolute value) than the nominal value derived from the estimate of mass loss through radiation and solar wind. Possible interpretations are discussed. ]]></content:encoded> <dc:title>Studying the Properties of Spacetime with an Improved Dynamical Model of the Inner Solar System</dc:title> <dc:creator>Dmitry Pavlov</dc:creator> <dc:creator>Ivan Dolgakov</dc:creator> <dc:identifier>doi: 10.3390/universe10110413</dc:identifier> <dc:source>Universe</dc:source> <dc:date>2024-11-03</dc:date> <prism:publicationName>Universe</prism:publicationName> <prism:publicationDate>2024-11-03</prism:publicationDate> <prism:volume>10</prism:volume> <prism:number>11</prism:number> <prism:section>Article</prism:section> <prism:startingPage>413</prism:startingPage> <prism:doi>10.3390/universe10110413</prism:doi> <prism:url>https://www.mdpi.com/2218-1997/10/11/413</prism:url> <cc:license rdf:resource="CC BY 4.0"/> </item> <item rdf:about="https://www.mdpi.com/2218-1997/10/11/412"> <title>Universe, Vol. 10, Pages 412: Analogous Hawking Radiation in Dispersive Media</title> <link>https://www.mdpi.com/2218-1997/10/11/412</link> <description>In the framework of the analogous Hawking effect, we significantly improve our previous analysis of the master equation that encompasses very relevant physical systems, like Bose&amp;ndash;Einstein condensates (BECs), dielectric media, and water. In particular, we are able to provide two significant improvements to the analysis. As our main result, we provide a complete set of connection formulas for both the subluminal and superluminal cases without resorting to suitable boundary conditions, first introduced by Corley, but simply on the grounds of a rigorous mathematical setting. Moreover, we provide an extension to the four-dimensional case, showing explicitly that, apart from obvious changes, adding transverse dimensions does not substantially modify the Hawking temperature in the dispersive case. Furthermore, an important class of exact solutions of the so-called reduced equation that governs the behavior of non-dispersive modes is also provided.</description> <pubDate>2024-11-02</pubDate> <content:encoded><![CDATA[ Universe, Vol. 10, Pages 412: Analogous Hawking Radiation in Dispersive Media Universe <a href="https://www.mdpi.com/2218-1997/10/11/412">doi: 10.3390/universe10110412</a> Authors: Francesco Belgiorno Sergio L. Cacciatori Simone Trevisan In the framework of the analogous Hawking effect, we significantly improve our previous analysis of the master equation that encompasses very relevant physical systems, like Bose&amp;ndash;Einstein condensates (BECs), dielectric media, and water. In particular, we are able to provide two significant improvements to the analysis. As our main result, we provide a complete set of connection formulas for both the subluminal and superluminal cases without resorting to suitable boundary conditions, first introduced by Corley, but simply on the grounds of a rigorous mathematical setting. Moreover, we provide an extension to the four-dimensional case, showing explicitly that, apart from obvious changes, adding transverse dimensions does not substantially modify the Hawking temperature in the dispersive case. Furthermore, an important class of exact solutions of the so-called reduced equation that governs the behavior of non-dispersive modes is also provided. ]]></content:encoded> <dc:title>Analogous Hawking Radiation in Dispersive Media</dc:title> <dc:creator>Francesco Belgiorno</dc:creator> <dc:creator>Sergio L. Cacciatori</dc:creator> <dc:creator>Simone Trevisan</dc:creator> <dc:identifier>doi: 10.3390/universe10110412</dc:identifier> <dc:source>Universe</dc:source> <dc:date>2024-11-02</dc:date> <prism:publicationName>Universe</prism:publicationName> <prism:publicationDate>2024-11-02</prism:publicationDate> <prism:volume>10</prism:volume> <prism:number>11</prism:number> <prism:section>Article</prism:section> <prism:startingPage>412</prism:startingPage> <prism:doi>10.3390/universe10110412</prism:doi> <prism:url>https://www.mdpi.com/2218-1997/10/11/412</prism:url> <cc:license rdf:resource="CC BY 4.0"/> </item> <item rdf:about="https://www.mdpi.com/2218-1997/10/11/411"> <title>Universe, Vol. 10, Pages 411: Structure Formation Through Magnetohydrodynamical Instabilities in Primordial Disks</title> <link>https://www.mdpi.com/2218-1997/10/11/411</link> <description>The shear flow instabilities under the presence of magnetic fields in the primordial disk can greatly facilitate the formation of density structures that serve as seeds prior to the onset of the gravitational Jeans instability. We evaluate the effects of the Parker, magnetorotational and kinematic dynamo instabilities by comparing the properties of these instabilities. We calculate the mass spectra of coagulated density structures by the above mechanism in the radial direction for an axisymmetric magnetohydrodynamic (MHD) torus equilibrium and power density profile models. Our local three-dimensional MHD simulation indicates that the coupling of the Parker and magnetorotational instability creates spiral arms and gas blobs in an accretion disk, reinforcing the theory and model. Such a mechanism for the early structure formation may be tested in a laboratory. The recent progress in experiments involving shear flows in rotating tokamak, field reversed configuration (FRC) and laser plasmas may become a key element to advance in nonlinear studies.</description> <pubDate>2024-10-31</pubDate> <content:encoded><![CDATA[ Universe, Vol. 10, Pages 411: Structure Formation Through Magnetohydrodynamical Instabilities in Primordial Disks Universe <a href="https://www.mdpi.com/2218-1997/10/11/411">doi: 10.3390/universe10110411</a> Authors: Koichi Noguchi Toshiki Tajima Wendell Horton The shear flow instabilities under the presence of magnetic fields in the primordial disk can greatly facilitate the formation of density structures that serve as seeds prior to the onset of the gravitational Jeans instability. We evaluate the effects of the Parker, magnetorotational and kinematic dynamo instabilities by comparing the properties of these instabilities. We calculate the mass spectra of coagulated density structures by the above mechanism in the radial direction for an axisymmetric magnetohydrodynamic (MHD) torus equilibrium and power density profile models. Our local three-dimensional MHD simulation indicates that the coupling of the Parker and magnetorotational instability creates spiral arms and gas blobs in an accretion disk, reinforcing the theory and model. Such a mechanism for the early structure formation may be tested in a laboratory. The recent progress in experiments involving shear flows in rotating tokamak, field reversed configuration (FRC) and laser plasmas may become a key element to advance in nonlinear studies. ]]></content:encoded> <dc:title>Structure Formation Through Magnetohydrodynamical Instabilities in Primordial Disks</dc:title> <dc:creator>Koichi Noguchi</dc:creator> <dc:creator>Toshiki Tajima</dc:creator> <dc:creator>Wendell Horton</dc:creator> <dc:identifier>doi: 10.3390/universe10110411</dc:identifier> <dc:source>Universe</dc:source> <dc:date>2024-10-31</dc:date> <prism:publicationName>Universe</prism:publicationName> <prism:publicationDate>2024-10-31</prism:publicationDate> <prism:volume>10</prism:volume> <prism:number>11</prism:number> <prism:section>Article</prism:section> <prism:startingPage>411</prism:startingPage> <prism:doi>10.3390/universe10110411</prism:doi> <prism:url>https://www.mdpi.com/2218-1997/10/11/411</prism:url> <cc:license rdf:resource="CC BY 4.0"/> </item> <item rdf:about="https://www.mdpi.com/2218-1997/10/11/410"> <title>Universe, Vol. 10, Pages 410: Relational Lorentzian Asymptotically Safe Quantum Gravity: Showcase Model</title> <link>https://www.mdpi.com/2218-1997/10/11/410</link> <description>In a recent contribution, we identified possible points of contact between the asymptotically safe and canonical approaches to quantum gravity. The idea is to start from the reduced phase space (often called relational) formulation of canonical quantum gravity, which provides a reduced (or physical) Hamiltonian for the true (observable) degrees of freedom. The resulting reduced phase space is then canonically quantized, and one can construct the generating functional of time-ordered Wightman (i.e., Feynman) or Schwinger distributions, respectively, from the corresponding time-translation unitary group or contraction semigroup, respectively, as a path integral. For the unitary choice, that path integral can be rewritten in terms of the Lorentzian Einstein&amp;ndash;Hilbert action plus observable matter action and a ghost action. The ghost action depends on the Hilbert space representation chosen for the canonical quantization and a reduction term that encodes the reduction of the full phase space to the phase space of observables. This path integral can then be treated with the methods of asymptotically safe quantum gravity in its Lorentzian version. We also exemplified the procedure using a concrete, minimalistic example, namely Einstein&amp;ndash;Klein&amp;ndash;Gordon theory, with as many neutral and massless scalar fields as there are spacetime dimensions. However, no explicit calculations were performed. In this paper, we fill in the missing steps. Particular care is needed due to the necessary switch to Lorentzian signature, which has a strong impact on the convergence of &amp;ldquo;heat&amp;rdquo; kernel time integrals in the heat kernel expansion of the trace involved in the Wetterich equation and which requires different cut-off functions than in the Euclidian version. As usual we truncate at relatively low order and derive and solve the resulting flow equations in that approximation.</description> <pubDate>2024-10-31</pubDate> <content:encoded><![CDATA[ Universe, Vol. 10, Pages 410: Relational Lorentzian Asymptotically Safe Quantum Gravity: Showcase Model Universe <a href="https://www.mdpi.com/2218-1997/10/11/410">doi: 10.3390/universe10110410</a> Authors: Renata Ferrero Thomas Thiemann In a recent contribution, we identified possible points of contact between the asymptotically safe and canonical approaches to quantum gravity. The idea is to start from the reduced phase space (often called relational) formulation of canonical quantum gravity, which provides a reduced (or physical) Hamiltonian for the true (observable) degrees of freedom. The resulting reduced phase space is then canonically quantized, and one can construct the generating functional of time-ordered Wightman (i.e., Feynman) or Schwinger distributions, respectively, from the corresponding time-translation unitary group or contraction semigroup, respectively, as a path integral. For the unitary choice, that path integral can be rewritten in terms of the Lorentzian Einstein&amp;ndash;Hilbert action plus observable matter action and a ghost action. The ghost action depends on the Hilbert space representation chosen for the canonical quantization and a reduction term that encodes the reduction of the full phase space to the phase space of observables. This path integral can then be treated with the methods of asymptotically safe quantum gravity in its Lorentzian version. We also exemplified the procedure using a concrete, minimalistic example, namely Einstein&amp;ndash;Klein&amp;ndash;Gordon theory, with as many neutral and massless scalar fields as there are spacetime dimensions. However, no explicit calculations were performed. In this paper, we fill in the missing steps. Particular care is needed due to the necessary switch to Lorentzian signature, which has a strong impact on the convergence of &amp;ldquo;heat&amp;rdquo; kernel time integrals in the heat kernel expansion of the trace involved in the Wetterich equation and which requires different cut-off functions than in the Euclidian version. As usual we truncate at relatively low order and derive and solve the resulting flow equations in that approximation. ]]></content:encoded> <dc:title>Relational Lorentzian Asymptotically Safe Quantum Gravity: Showcase Model</dc:title> <dc:creator>Renata Ferrero</dc:creator> <dc:creator>Thomas Thiemann</dc:creator> <dc:identifier>doi: 10.3390/universe10110410</dc:identifier> <dc:source>Universe</dc:source> <dc:date>2024-10-31</dc:date> <prism:publicationName>Universe</prism:publicationName> <prism:publicationDate>2024-10-31</prism:publicationDate> <prism:volume>10</prism:volume> <prism:number>11</prism:number> <prism:section>Article</prism:section> <prism:startingPage>410</prism:startingPage> <prism:doi>10.3390/universe10110410</prism:doi> <prism:url>https://www.mdpi.com/2218-1997/10/11/410</prism:url> <cc:license rdf:resource="CC BY 4.0"/> </item> <item rdf:about="https://www.mdpi.com/2218-1997/10/11/409"> <title>Universe, Vol. 10, Pages 409: An Update of the Hypothetical X17 Particle</title> <link>https://www.mdpi.com/2218-1997/10/11/409</link> <description>Recently, when examining the differential internal pair creation coefficients of 8Be, 4He and 12C nuclei, we observed peak-like anomalies in the angular correlation of the e+e&amp;minus; pairs. This was interpreted as the creation and immediate decay of an intermediate bosonic particle with a mass of mXc2&amp;asymp; 17 MeV, receiving the name X17 in subsequent publications. In this paper, our latest results obtained for the X17 particle are presented by investigating the e+e&amp;minus; pair correlations in the decay of the Giant Dipole Resonance (GDR) of 8Be. Our results initiated a significant number of new experiments all over the world to detect the X17 particle and determine its properties. In this paper, we will also conduct a mini-review of the experiments whose results are already published, as well as the ones closest to being published.</description> <pubDate>2024-10-31</pubDate> <content:encoded><![CDATA[ Universe, Vol. 10, Pages 409: An Update of the Hypothetical X17 Particle Universe <a href="https://www.mdpi.com/2218-1997/10/11/409">doi: 10.3390/universe10110409</a> Authors: Attila J. Krasznahorkay Attila Krasznahorkay Margit Csatl贸s J谩nos Tim谩r Marcell Begala Attila Krak贸 Istv谩n Rajta Istv谩n Vajda N谩ndor J. Sas Recently, when examining the differential internal pair creation coefficients of 8Be, 4He and 12C nuclei, we observed peak-like anomalies in the angular correlation of the e+e&amp;minus; pairs. This was interpreted as the creation and immediate decay of an intermediate bosonic particle with a mass of mXc2&amp;asymp; 17 MeV, receiving the name X17 in subsequent publications. In this paper, our latest results obtained for the X17 particle are presented by investigating the e+e&amp;minus; pair correlations in the decay of the Giant Dipole Resonance (GDR) of 8Be. Our results initiated a significant number of new experiments all over the world to detect the X17 particle and determine its properties. In this paper, we will also conduct a mini-review of the experiments whose results are already published, as well as the ones closest to being published. ]]></content:encoded> <dc:title>An Update of the Hypothetical X17 Particle</dc:title> <dc:creator>Attila J. Krasznahorkay</dc:creator> <dc:creator>Attila Krasznahorkay</dc:creator> <dc:creator>Margit Csatl贸s</dc:creator> <dc:creator>J谩nos Tim谩r</dc:creator> <dc:creator>Marcell Begala</dc:creator> <dc:creator>Attila Krak贸</dc:creator> <dc:creator>Istv谩n Rajta</dc:creator> <dc:creator>Istv谩n Vajda</dc:creator> <dc:creator>N谩ndor J. Sas</dc:creator> <dc:identifier>doi: 10.3390/universe10110409</dc:identifier> <dc:source>Universe</dc:source> <dc:date>2024-10-31</dc:date> <prism:publicationName>Universe</prism:publicationName> <prism:publicationDate>2024-10-31</prism:publicationDate> <prism:volume>10</prism:volume> <prism:number>11</prism:number> <prism:section>Article</prism:section> <prism:startingPage>409</prism:startingPage> <prism:doi>10.3390/universe10110409</prism:doi> <prism:url>https://www.mdpi.com/2218-1997/10/11/409</prism:url> <cc:license rdf:resource="CC BY 4.0"/> </item> <item rdf:about="https://www.mdpi.com/2218-1997/10/11/408"> <title>Universe, Vol. 10, Pages 408: Generalized Schwarzschild Spacetimes with a Linear Term and a Cosmological Constant</title> <link>https://www.mdpi.com/2218-1997/10/11/408</link> <description>Particular Kottler spacetimes are analytically investigated. The investigated spacetimes are spherically symmetric nonrotating spacetimes endowed with a Schwarzschild solid-angle element. SchwarzschildNairiai spacetimes, Schwarzschild spacetimes with a linear term, and Schwarzschild spacetimes with a linear term and a cosmological constant are studied. The infinite-redshift surfaces are analytically written. To this aim, the parameter spaces of the models are analytically investigated, and the conditions for which the analytical radii are reconducted to the physical horizons are used to set and to constrain the parameter spaces. The coordinate-singularity-avoiding coordinate extensions are newly written. Schwarzschild spacetimes with a linear term and a cosmological constant termare analytically studied, and the new singularity-avoiding coordinate extensions are detailed. The new roles of the linear term and of the cosmological constant term in characterizing the Schwarzschild radius are traced. The generalized Schwarzschild&amp;ndash;deSitter case and generalized Schwarzschild&amp;ndash;anti-deSitter case are characterized in a different manner. The weak field limit is newly recalled. The embeddings are newly provided. The quantum implementation is newly envisaged. The geometrical objects are newly calculated. As a result, for the Einstein field equations, the presence of quintessence is newly excluded. The Birkhoff theorem is newly proven to be obeyed.</description> <pubDate>2024-10-30</pubDate> <content:encoded><![CDATA[ Universe, Vol. 10, Pages 408: Generalized Schwarzschild Spacetimes with a Linear Term and a Cosmological Constant Universe <a href="https://www.mdpi.com/2218-1997/10/11/408">doi: 10.3390/universe10110408</a> Authors: Orchidea Maria Lecian Particular Kottler spacetimes are analytically investigated. The investigated spacetimes are spherically symmetric nonrotating spacetimes endowed with a Schwarzschild solid-angle element. SchwarzschildNairiai spacetimes, Schwarzschild spacetimes with a linear term, and Schwarzschild spacetimes with a linear term and a cosmological constant are studied. The infinite-redshift surfaces are analytically written. To this aim, the parameter spaces of the models are analytically investigated, and the conditions for which the analytical radii are reconducted to the physical horizons are used to set and to constrain the parameter spaces. The coordinate-singularity-avoiding coordinate extensions are newly written. Schwarzschild spacetimes with a linear term and a cosmological constant termare analytically studied, and the new singularity-avoiding coordinate extensions are detailed. The new roles of the linear term and of the cosmological constant term in characterizing the Schwarzschild radius are traced. The generalized Schwarzschild&amp;ndash;deSitter case and generalized Schwarzschild&amp;ndash;anti-deSitter case are characterized in a different manner. The weak field limit is newly recalled. The embeddings are newly provided. The quantum implementation is newly envisaged. The geometrical objects are newly calculated. As a result, for the Einstein field equations, the presence of quintessence is newly excluded. The Birkhoff theorem is newly proven to be obeyed. ]]></content:encoded> <dc:title>Generalized Schwarzschild Spacetimes with a Linear Term and a Cosmological Constant</dc:title> <dc:creator>Orchidea Maria Lecian</dc:creator> <dc:identifier>doi: 10.3390/universe10110408</dc:identifier> <dc:source>Universe</dc:source> <dc:date>2024-10-30</dc:date> <prism:publicationName>Universe</prism:publicationName> <prism:publicationDate>2024-10-30</prism:publicationDate> <prism:volume>10</prism:volume> <prism:number>11</prism:number> <prism:section>Article</prism:section> <prism:startingPage>408</prism:startingPage> <prism:doi>10.3390/universe10110408</prism:doi> <prism:url>https://www.mdpi.com/2218-1997/10/11/408</prism:url> <cc:license rdf:resource="CC BY 4.0"/> </item> <item rdf:about="https://www.mdpi.com/2218-1997/10/11/407"> <title>Universe, Vol. 10, Pages 407: Ultra-Low Frequency Waves of Foreshock Origin Upstream and Inside of the Magnetospheres of Earth, Mercury, and Saturn Related to Solar Wind&ndash;Magnetosphere Coupling</title> <link>https://www.mdpi.com/2218-1997/10/11/407</link> <description>This review examines ultra-low frequency (ULF) waves across different planetary environments, focusing on Earth, Mercury, and Saturn. Data from spacecraft missions (CHAMP, Swarm, and Oersted for Earth; MESSENGER for Mercury; and Cassini for Saturn) provide insights into ULF wave dynamics. At Earth, compressional ULF waves, particularly Pc3 waves, show significant power near the equator and peak around Magnetic Local Time (MLT) = 11. These waves interact complexly with Alfv&amp;eacute;n waves, impacting ionospheric responses and geomagnetic field line resonances. At Mercury, ULF waves transition from circular to linear polarization, indicating resonant interactions influenced by compressional components. MESSENGER data reveal a lower occurrence rate of ULF waves in Mercury&amp;rsquo;s foreshock compared to Earth&amp;rsquo;s, attributed to reduced backstreaming protons and lower solar wind Alfv&amp;eacute;nic Mach numbers, as ULF wave activity increases with heliocentric distance. Short Large-Amplitude Magnetic Structures (SLAMS) observed at Mercury and Saturn show distinct characteristics compared to those of Earth, including the presence of whistler precursos waves. However, due to the large differences in heliospheric distances, SLAMS (their temporal scale size correlate with the ULF wave frequency) at Mercury are significantly shorter in duration than at Earth or Saturn, since the ULF wave frequency primarily depends on the strength of the interplanetary magnetic field. This review highlights the variability of ULF waves and SLAMS across planetary environments, emphasizing Earth&amp;rsquo;s well-understood ionospheric interactions and the unique behaviours observed for Mercury and Saturn. These findings enhance our understanding of space plasma dynamics and underline the need for further research regarding planetary magnetospheres.</description> <pubDate>2024-10-30</pubDate> <content:encoded><![CDATA[ Universe, Vol. 10, Pages 407: Ultra-Low Frequency Waves of Foreshock Origin Upstream and Inside of the Magnetospheres of Earth, Mercury, and Saturn Related to Solar Wind&ndash;Magnetosphere Coupling Universe <a href="https://www.mdpi.com/2218-1997/10/11/407">doi: 10.3390/universe10110407</a> Authors: Zsofia Bebesi Navin Kumar Dwivedi Arpad Kis Antal Juh谩sz Balazs Heilig This review examines ultra-low frequency (ULF) waves across different planetary environments, focusing on Earth, Mercury, and Saturn. Data from spacecraft missions (CHAMP, Swarm, and Oersted for Earth; MESSENGER for Mercury; and Cassini for Saturn) provide insights into ULF wave dynamics. At Earth, compressional ULF waves, particularly Pc3 waves, show significant power near the equator and peak around Magnetic Local Time (MLT) = 11. These waves interact complexly with Alfv&amp;eacute;n waves, impacting ionospheric responses and geomagnetic field line resonances. At Mercury, ULF waves transition from circular to linear polarization, indicating resonant interactions influenced by compressional components. MESSENGER data reveal a lower occurrence rate of ULF waves in Mercury&amp;rsquo;s foreshock compared to Earth&amp;rsquo;s, attributed to reduced backstreaming protons and lower solar wind Alfv&amp;eacute;nic Mach numbers, as ULF wave activity increases with heliocentric distance. Short Large-Amplitude Magnetic Structures (SLAMS) observed at Mercury and Saturn show distinct characteristics compared to those of Earth, including the presence of whistler precursos waves. However, due to the large differences in heliospheric distances, SLAMS (their temporal scale size correlate with the ULF wave frequency) at Mercury are significantly shorter in duration than at Earth or Saturn, since the ULF wave frequency primarily depends on the strength of the interplanetary magnetic field. This review highlights the variability of ULF waves and SLAMS across planetary environments, emphasizing Earth&amp;rsquo;s well-understood ionospheric interactions and the unique behaviours observed for Mercury and Saturn. These findings enhance our understanding of space plasma dynamics and underline the need for further research regarding planetary magnetospheres. ]]></content:encoded> <dc:title>Ultra-Low Frequency Waves of Foreshock Origin Upstream and Inside of the Magnetospheres of Earth, Mercury, and Saturn Related to Solar Wind&amp;ndash;Magnetosphere Coupling</dc:title> <dc:creator>Zsofia Bebesi</dc:creator> <dc:creator>Navin Kumar Dwivedi</dc:creator> <dc:creator>Arpad Kis</dc:creator> <dc:creator>Antal Juh谩sz</dc:creator> <dc:creator>Balazs Heilig</dc:creator> <dc:identifier>doi: 10.3390/universe10110407</dc:identifier> <dc:source>Universe</dc:source> <dc:date>2024-10-30</dc:date> <prism:publicationName>Universe</prism:publicationName> <prism:publicationDate>2024-10-30</prism:publicationDate> <prism:volume>10</prism:volume> <prism:number>11</prism:number> <prism:section>Review</prism:section> <prism:startingPage>407</prism:startingPage> <prism:doi>10.3390/universe10110407</prism:doi> <prism:url>https://www.mdpi.com/2218-1997/10/11/407</prism:url> <cc:license rdf:resource="CC BY 4.0"/> </item> <item rdf:about="https://www.mdpi.com/2218-1997/10/11/406"> <title>Universe, Vol. 10, Pages 406: 2D BAO vs. 3D BAO: Solving the Hubble Tension with Bimetric Cosmology</title> <link>https://www.mdpi.com/2218-1997/10/11/406</link> <description>Ordinary 3D Baryon Acoustic Oscillations (BAO) data are model-dependent, requiring the assumption of a cosmological model to calculate comoving distances during data reduction. Throughout the present-day literature, the assumed model is &amp;Lambda;CDM. However, it has been pointed out in several recent works that this assumption can be inadequate when analyzing alternative cosmologies, potentially biasing the Hubble constant (H0) low, thus contributing to the Hubble tension. To address this issue, 3D BAO data can be replaced with 2D BAO data, which are only weakly model-dependent. The impact of using 2D BAO data, in combination with alternative cosmological models beyond &amp;Lambda;CDM, has been explored for several phenomenological models, showing a promising reduction in the Hubble tension. In this work, we accommodate these models in the theoretically robust framework of bimetric gravity. This is a modified theory of gravity that exhibits a transition from a (possibly) negative cosmological constant in the early universe to a positive one in the late universe. By combining 2D BAO data with cosmic microwave background and type Ia supernovae data, we find that the inverse distance ladder in this theory yields a Hubble constant of H0=(71.0&amp;plusmn;0.9)km/s/Mpc, consistent with the SH0ES local distance ladder measurement of H0=(73.0&amp;plusmn;1.0)km/s/Mpc. Replacing 2D BAO with 3D BAO results in H0=(68.6&amp;plusmn;0.5)km/s/Mpc from the inverse distance ladder. We conclude that the choice of BAO data significantly impacts the Hubble tension, with ordinary 3D BAO data exacerbating the tension, while 2D BAO data provide results consistent with the local distance ladder.</description> <pubDate>2024-10-28</pubDate> <content:encoded><![CDATA[ Universe, Vol. 10, Pages 406: 2D BAO vs. 3D BAO: Solving the Hubble Tension with Bimetric Cosmology Universe <a href="https://www.mdpi.com/2218-1997/10/11/406">doi: 10.3390/universe10110406</a> Authors: Sowmaydeep Dwivedi Marcus H枚g氓s Ordinary 3D Baryon Acoustic Oscillations (BAO) data are model-dependent, requiring the assumption of a cosmological model to calculate comoving distances during data reduction. Throughout the present-day literature, the assumed model is &amp;Lambda;CDM. However, it has been pointed out in several recent works that this assumption can be inadequate when analyzing alternative cosmologies, potentially biasing the Hubble constant (H0) low, thus contributing to the Hubble tension. To address this issue, 3D BAO data can be replaced with 2D BAO data, which are only weakly model-dependent. The impact of using 2D BAO data, in combination with alternative cosmological models beyond &amp;Lambda;CDM, has been explored for several phenomenological models, showing a promising reduction in the Hubble tension. In this work, we accommodate these models in the theoretically robust framework of bimetric gravity. This is a modified theory of gravity that exhibits a transition from a (possibly) negative cosmological constant in the early universe to a positive one in the late universe. By combining 2D BAO data with cosmic microwave background and type Ia supernovae data, we find that the inverse distance ladder in this theory yields a Hubble constant of H0=(71.0&amp;plusmn;0.9)km/s/Mpc, consistent with the SH0ES local distance ladder measurement of H0=(73.0&amp;plusmn;1.0)km/s/Mpc. Replacing 2D BAO with 3D BAO results in H0=(68.6&amp;plusmn;0.5)km/s/Mpc from the inverse distance ladder. We conclude that the choice of BAO data significantly impacts the Hubble tension, with ordinary 3D BAO data exacerbating the tension, while 2D BAO data provide results consistent with the local distance ladder. ]]></content:encoded> <dc:title>2D BAO vs. 3D BAO: Solving the Hubble Tension with Bimetric Cosmology</dc:title> <dc:creator>Sowmaydeep Dwivedi</dc:creator> <dc:creator>Marcus H枚g氓s</dc:creator> <dc:identifier>doi: 10.3390/universe10110406</dc:identifier> <dc:source>Universe</dc:source> <dc:date>2024-10-28</dc:date> <prism:publicationName>Universe</prism:publicationName> <prism:publicationDate>2024-10-28</prism:publicationDate> <prism:volume>10</prism:volume> <prism:number>11</prism:number> <prism:section>Article</prism:section> <prism:startingPage>406</prism:startingPage> <prism:doi>10.3390/universe10110406</prism:doi> <prism:url>https://www.mdpi.com/2218-1997/10/11/406</prism:url> <cc:license rdf:resource="CC BY 4.0"/> </item> <item rdf:about="https://www.mdpi.com/2218-1997/10/11/405"> <title>Universe, Vol. 10, Pages 405: Leveraging the Interplanetary Superhighway for Propellant&ndash;Optimal Orbit Insertion into Saturn&ndash;Titan System</title> <link>https://www.mdpi.com/2218-1997/10/11/405</link> <description>This paper presents an innovative approach using Dynamical Systems Theory (DST) for interplanetary orbit insertion into Saturn&amp;minus;Titan three&amp;minus;body orbits. By leveraging DST, this study identifies invariant manifolds guiding a spacecraft into Titan&amp;minus;centered Distant Retrograde Orbits (DROs), strategically selected for their scientific significance. Subsequently, Particle Swarm Optimization (PSO) is employed to fine&amp;minus;tune the insertion parameters, thereby minimizing &amp;Delta;V. The results demonstrate that the proposed method allows for a reduction in &amp;Delta;V of over 70% compared to conventional approaches like patched conics&amp;minus;based flybys (2.68 km/s vs. 9.23 km/s), albeit with an extended time of flight, which remains notably faster than weak stability boundary transfers. This paper serves as an interplanetary mission planning methodology to optimize spacecraft trajectories for the exploration of the Saturn&amp;minus;Titan system.</description> <pubDate>2024-10-28</pubDate> <content:encoded><![CDATA[ Universe, Vol. 10, Pages 405: Leveraging the Interplanetary Superhighway for Propellant&ndash;Optimal Orbit Insertion into Saturn&ndash;Titan System Universe <a href="https://www.mdpi.com/2218-1997/10/11/405">doi: 10.3390/universe10110405</a> Authors: Giuseppe Papalia Davide Conte This paper presents an innovative approach using Dynamical Systems Theory (DST) for interplanetary orbit insertion into Saturn&amp;minus;Titan three&amp;minus;body orbits. By leveraging DST, this study identifies invariant manifolds guiding a spacecraft into Titan&amp;minus;centered Distant Retrograde Orbits (DROs), strategically selected for their scientific significance. Subsequently, Particle Swarm Optimization (PSO) is employed to fine&amp;minus;tune the insertion parameters, thereby minimizing &amp;Delta;V. The results demonstrate that the proposed method allows for a reduction in &amp;Delta;V of over 70% compared to conventional approaches like patched conics&amp;minus;based flybys (2.68 km/s vs. 9.23 km/s), albeit with an extended time of flight, which remains notably faster than weak stability boundary transfers. This paper serves as an interplanetary mission planning methodology to optimize spacecraft trajectories for the exploration of the Saturn&amp;minus;Titan system. ]]></content:encoded> <dc:title>Leveraging the Interplanetary Superhighway for Propellant&amp;ndash;Optimal Orbit Insertion into Saturn&amp;ndash;Titan System</dc:title> <dc:creator>Giuseppe Papalia</dc:creator> <dc:creator>Davide Conte</dc:creator> <dc:identifier>doi: 10.3390/universe10110405</dc:identifier> <dc:source>Universe</dc:source> <dc:date>2024-10-28</dc:date> <prism:publicationName>Universe</prism:publicationName> <prism:publicationDate>2024-10-28</prism:publicationDate> <prism:volume>10</prism:volume> <prism:number>11</prism:number> <prism:section>Article</prism:section> <prism:startingPage>405</prism:startingPage> <prism:doi>10.3390/universe10110405</prism:doi> <prism:url>https://www.mdpi.com/2218-1997/10/11/405</prism:url> <cc:license rdf:resource="CC BY 4.0"/> </item> <item rdf:about="https://www.mdpi.com/2218-1997/10/11/404"> <title>Universe, Vol. 10, Pages 404: The Variation of G and &Lambda; in Cosmology</title> <link>https://www.mdpi.com/2218-1997/10/11/404</link> <description>The idea of varying constants of nature is very old, and has commanded a lot of attention since first mooted. The variation in the gravitational parameter G and cosmological parameter &amp;Lambda; is still an active area of research. Since the idea of a varying G was introduced by Dirac almost a century ago, there are even theories that have variable G such as the Brans&amp;ndash;Dicke theory and the scale covariant theory. Both these theories also have a varying &amp;Lambda; in their full generalisations. A varying &amp;Lambda; was also introduced around the same time as that of varying G. It is interesting to note that a possible solution to the cosmological constant problem can be realised from a dynamic &amp;Lambda;. In this work, we focus on a varying &amp;Lambda; and G framework. In almost all studies in the simplest framework of variables &amp;Lambda; and G, it is found that one of them has to increase with time. However, observations and theoretical considerations indicate that both &amp;Lambda; and G should decrease with time. In this paper, we propose a solution to this problem, finding theories in which both &amp;Lambda; and G decrease with time.</description> <pubDate>2024-10-23</pubDate> <content:encoded><![CDATA[ Universe, Vol. 10, Pages 404: The Variation of G and &Lambda; in Cosmology Universe <a href="https://www.mdpi.com/2218-1997/10/11/404">doi: 10.3390/universe10110404</a> Authors: Aroonkumar Beesham The idea of varying constants of nature is very old, and has commanded a lot of attention since first mooted. The variation in the gravitational parameter G and cosmological parameter &amp;Lambda; is still an active area of research. Since the idea of a varying G was introduced by Dirac almost a century ago, there are even theories that have variable G such as the Brans&amp;ndash;Dicke theory and the scale covariant theory. Both these theories also have a varying &amp;Lambda; in their full generalisations. A varying &amp;Lambda; was also introduced around the same time as that of varying G. It is interesting to note that a possible solution to the cosmological constant problem can be realised from a dynamic &amp;Lambda;. In this work, we focus on a varying &amp;Lambda; and G framework. In almost all studies in the simplest framework of variables &amp;Lambda; and G, it is found that one of them has to increase with time. However, observations and theoretical considerations indicate that both &amp;Lambda; and G should decrease with time. In this paper, we propose a solution to this problem, finding theories in which both &amp;Lambda; and G decrease with time. ]]></content:encoded> <dc:title>The Variation of G and &amp;Lambda; in Cosmology</dc:title> <dc:creator>Aroonkumar Beesham</dc:creator> <dc:identifier>doi: 10.3390/universe10110404</dc:identifier> <dc:source>Universe</dc:source> <dc:date>2024-10-23</dc:date> <prism:publicationName>Universe</prism:publicationName> <prism:publicationDate>2024-10-23</prism:publicationDate> <prism:volume>10</prism:volume> <prism:number>11</prism:number> <prism:section>Article</prism:section> <prism:startingPage>404</prism:startingPage> <prism:doi>10.3390/universe10110404</prism:doi> <prism:url>https://www.mdpi.com/2218-1997/10/11/404</prism:url> <cc:license rdf:resource="CC BY 4.0"/> </item> <item rdf:about="https://www.mdpi.com/2218-1997/10/10/403"> <title>Universe, Vol. 10, Pages 403: Off-Axis Color Characteristics of Binary Neutron Star Merger Events: Applications for Space Multi-Band Variable Object Monitor and James Webb Space Telescope</title> <link>https://www.mdpi.com/2218-1997/10/10/403</link> <description>With advancements in gravitational wave detection technology, an increasing number of binary neutron star (BNS) merger events are expected to be detected. Due to the narrow opening angle of jet cores, many BNS merger events occur off-axis, resulting in numerous gamma-ray bursts (GRBs) going undetected. Models suggest that kilonovae, which can be observed off-axis, offer more opportunities to be detected in the optical/near-infrared band as electromagnetic counterparts of BNS merger events. In this study, we calculate kilonova emission using a three-dimensional semi-analytical code and model the GRB afterglow emission with the open-source Python package afterglowpy at various inclination angles. Our results show that it is possible to identify the kilonova signal from the observed color evolution of BNS merger events. We also deduce the optimal observing window for SVOM/VT and JWST/NIRCam, which depends on the viewing angle, jet opening angle, and circumburst density. These parameters can be cross-checked with the multi-band afterglow fitting. We suggest that kilonovae are more likely to be identified at larger inclination angles, which can also help determine whether the observed signals without accompanying GRBs originate from BNS mergers.</description> <pubDate>2024-10-19</pubDate> <content:encoded><![CDATA[ Universe, Vol. 10, Pages 403: Off-Axis Color Characteristics of Binary Neutron Star Merger Events: Applications for Space Multi-Band Variable Object Monitor and James Webb Space Telescope Universe <a href="https://www.mdpi.com/2218-1997/10/10/403">doi: 10.3390/universe10100403</a> Authors: Hongyu Gong Daming Wei Zhiping Jin With advancements in gravitational wave detection technology, an increasing number of binary neutron star (BNS) merger events are expected to be detected. Due to the narrow opening angle of jet cores, many BNS merger events occur off-axis, resulting in numerous gamma-ray bursts (GRBs) going undetected. Models suggest that kilonovae, which can be observed off-axis, offer more opportunities to be detected in the optical/near-infrared band as electromagnetic counterparts of BNS merger events. In this study, we calculate kilonova emission using a three-dimensional semi-analytical code and model the GRB afterglow emission with the open-source Python package afterglowpy at various inclination angles. Our results show that it is possible to identify the kilonova signal from the observed color evolution of BNS merger events. We also deduce the optimal observing window for SVOM/VT and JWST/NIRCam, which depends on the viewing angle, jet opening angle, and circumburst density. These parameters can be cross-checked with the multi-band afterglow fitting. We suggest that kilonovae are more likely to be identified at larger inclination angles, which can also help determine whether the observed signals without accompanying GRBs originate from BNS mergers. ]]></content:encoded> <dc:title>Off-Axis Color Characteristics of Binary Neutron Star Merger Events: Applications for Space Multi-Band Variable Object Monitor and James Webb Space Telescope</dc:title> <dc:creator>Hongyu Gong</dc:creator> <dc:creator>Daming Wei</dc:creator> <dc:creator>Zhiping Jin</dc:creator> <dc:identifier>doi: 10.3390/universe10100403</dc:identifier> <dc:source>Universe</dc:source> <dc:date>2024-10-19</dc:date> <prism:publicationName>Universe</prism:publicationName> <prism:publicationDate>2024-10-19</prism:publicationDate> <prism:volume>10</prism:volume> <prism:number>10</prism:number> <prism:section>Article</prism:section> <prism:startingPage>403</prism:startingPage> <prism:doi>10.3390/universe10100403</prism:doi> <prism:url>https://www.mdpi.com/2218-1997/10/10/403</prism:url> <cc:license rdf:resource="CC BY 4.0"/> </item> <item rdf:about="https://www.mdpi.com/2218-1997/10/10/402"> <title>Universe, Vol. 10, Pages 402: Spinor&ndash;Vector Duality and Mirror Symmetry</title> <link>https://www.mdpi.com/2218-1997/10/10/402</link> <description>Mirror symmetry was first observed in worldsheet string constructions, and was shown to have profound implications in the Effective Field Theory (EFT) limit of string compactifications, and for the properties of Calabi&amp;ndash;Yau manifolds. It opened up a new field in pure mathematics, and was utilised in the area of enumerative geometry. Spinor&amp;ndash;Vector Duality (SVD) is an extension of mirror symmetry. This can be readily understood in terms of the moduli of toroidal compactification of the Heterotic String, which includes the metric the antisymmetric tensor field and the Wilson line moduli. In terms of the toroidal moduli, mirror symmetry corresponds to mappings of the internal space moduli, whereas Spinor&amp;ndash;Vector Duality corresponds to maps of the Wilson line moduli. In the past few of years, we demonstrated the existence of Spinor&amp;ndash;Vector Duality in the effective field theory compactifications of string theories. This was achieved by starting with a worldsheet orbifold construction that exhibited Spinor&amp;ndash;Vector Duality and resolving the orbifold singularities, hence generating a smooth, effective field theory limit with an imprint of the Spinor&amp;ndash;Vector Duality. Just like mirror symmetry, the Spinor&amp;ndash;Vector Duality can be used to study the properties of complex manifolds with vector bundles. Spinor&amp;ndash;Vector Duality offers a top-down approach to the &amp;ldquo;Swampland&amp;rdquo; program, by exploring the imprint of the symmetries of the ultra-violet complete worldsheet string constructions in the effective field theory limit. The SVD suggests a demarcation line between (2,0) EFTs that possess an ultra-violet complete embedding versus those that do not.</description> <pubDate>2024-10-19</pubDate> <content:encoded><![CDATA[ Universe, Vol. 10, Pages 402: Spinor&ndash;Vector Duality and Mirror Symmetry Universe <a href="https://www.mdpi.com/2218-1997/10/10/402">doi: 10.3390/universe10100402</a> Authors: Alon E. Faraggi Mirror symmetry was first observed in worldsheet string constructions, and was shown to have profound implications in the Effective Field Theory (EFT) limit of string compactifications, and for the properties of Calabi&amp;ndash;Yau manifolds. It opened up a new field in pure mathematics, and was utilised in the area of enumerative geometry. Spinor&amp;ndash;Vector Duality (SVD) is an extension of mirror symmetry. This can be readily understood in terms of the moduli of toroidal compactification of the Heterotic String, which includes the metric the antisymmetric tensor field and the Wilson line moduli. In terms of the toroidal moduli, mirror symmetry corresponds to mappings of the internal space moduli, whereas Spinor&amp;ndash;Vector Duality corresponds to maps of the Wilson line moduli. In the past few of years, we demonstrated the existence of Spinor&amp;ndash;Vector Duality in the effective field theory compactifications of string theories. This was achieved by starting with a worldsheet orbifold construction that exhibited Spinor&amp;ndash;Vector Duality and resolving the orbifold singularities, hence generating a smooth, effective field theory limit with an imprint of the Spinor&amp;ndash;Vector Duality. Just like mirror symmetry, the Spinor&amp;ndash;Vector Duality can be used to study the properties of complex manifolds with vector bundles. Spinor&amp;ndash;Vector Duality offers a top-down approach to the &amp;ldquo;Swampland&amp;rdquo; program, by exploring the imprint of the symmetries of the ultra-violet complete worldsheet string constructions in the effective field theory limit. The SVD suggests a demarcation line between (2,0) EFTs that possess an ultra-violet complete embedding versus those that do not. ]]></content:encoded> <dc:title>Spinor&amp;ndash;Vector Duality and Mirror Symmetry</dc:title> <dc:creator>Alon E. Faraggi</dc:creator> <dc:identifier>doi: 10.3390/universe10100402</dc:identifier> <dc:source>Universe</dc:source> <dc:date>2024-10-19</dc:date> <prism:publicationName>Universe</prism:publicationName> <prism:publicationDate>2024-10-19</prism:publicationDate> <prism:volume>10</prism:volume> <prism:number>10</prism:number> <prism:section>Article</prism:section> <prism:startingPage>402</prism:startingPage> <prism:doi>10.3390/universe10100402</prism:doi> <prism:url>https://www.mdpi.com/2218-1997/10/10/402</prism:url> <cc:license rdf:resource="CC BY 4.0"/> </item> <item rdf:about="https://www.mdpi.com/2218-1997/10/10/401"> <title>Universe, Vol. 10, Pages 401: Corrections on the Distribution of Nuclei Due to Neutron Degeneracy and Its Effect on R-Process in Neutron Star Black Hole Mergers</title> <link>https://www.mdpi.com/2218-1997/10/10/401</link> <description>The r-process is one of the processes that produces heavy elements in the Universe. One of its possible astrophysical sites is the neutron star&amp;ndash;black hole (NS-BH) merger. We first show that the neutrons can degenerate before and during the r-process in these mergers. Previous studies assumed neutrons were non-degenerate and the related rates were calculated under Maxwell&amp;ndash;Boltzmann approximations. Hence, we corrected the related rates with neutron degeneracy put in the network code and calculated with the trajectories of NS-BH mergers. We show that there are differences in the nuclei distributions. The heating rates and the temperature at most can be two times larger. The change in heating rates and temperature can affect the light curves of the kilonovae. However, this has little effect on the final abundances.</description> <pubDate>2024-10-18</pubDate> <content:encoded><![CDATA[ Universe, Vol. 10, Pages 401: Corrections on the Distribution of Nuclei Due to Neutron Degeneracy and Its Effect on R-Process in Neutron Star Black Hole Mergers Universe <a href="https://www.mdpi.com/2218-1997/10/10/401">doi: 10.3390/universe10100401</a> Authors: Rita K. Y. Lau The r-process is one of the processes that produces heavy elements in the Universe. One of its possible astrophysical sites is the neutron star&amp;ndash;black hole (NS-BH) merger. We first show that the neutrons can degenerate before and during the r-process in these mergers. Previous studies assumed neutrons were non-degenerate and the related rates were calculated under Maxwell&amp;ndash;Boltzmann approximations. Hence, we corrected the related rates with neutron degeneracy put in the network code and calculated with the trajectories of NS-BH mergers. We show that there are differences in the nuclei distributions. The heating rates and the temperature at most can be two times larger. The change in heating rates and temperature can affect the light curves of the kilonovae. However, this has little effect on the final abundances. ]]></content:encoded> <dc:title>Corrections on the Distribution of Nuclei Due to Neutron Degeneracy and Its Effect on R-Process in Neutron Star Black Hole Mergers</dc:title> <dc:creator>Rita K. Y. Lau</dc:creator> <dc:identifier>doi: 10.3390/universe10100401</dc:identifier> <dc:source>Universe</dc:source> <dc:date>2024-10-18</dc:date> <prism:publicationName>Universe</prism:publicationName> <prism:publicationDate>2024-10-18</prism:publicationDate> <prism:volume>10</prism:volume> <prism:number>10</prism:number> <prism:section>Article</prism:section> <prism:startingPage>401</prism:startingPage> <prism:doi>10.3390/universe10100401</prism:doi> <prism:url>https://www.mdpi.com/2218-1997/10/10/401</prism:url> <cc:license rdf:resource="CC BY 4.0"/> </item> <item rdf:about="https://www.mdpi.com/2218-1997/10/10/400"> <title>Universe, Vol. 10, Pages 400: An Infinitely Old Universe with Planck Fields Before and After the Big Bang</title> <link>https://www.mdpi.com/2218-1997/10/10/400</link> <description>The Robertson&amp;ndash;Walker minimum length (RWML) theory considers stochastically perturbed spacetime to describe an expanding universe governed by geometry and diffusion. We explore the possibility of static, torsionless universe eras with conserved energy density. We find that the RWML theory provides asymptotically static equations of state under positive curvature both far in the past and far into the future, with a Big Bang singularity in between.</description> <pubDate>2024-10-17</pubDate> <content:encoded><![CDATA[ Universe, Vol. 10, Pages 400: An Infinitely Old Universe with Planck Fields Before and After the Big Bang Universe <a href="https://www.mdpi.com/2218-1997/10/10/400">doi: 10.3390/universe10100400</a> Authors: Dragana Pilipovi膰 The Robertson&amp;ndash;Walker minimum length (RWML) theory considers stochastically perturbed spacetime to describe an expanding universe governed by geometry and diffusion. We explore the possibility of static, torsionless universe eras with conserved energy density. We find that the RWML theory provides asymptotically static equations of state under positive curvature both far in the past and far into the future, with a Big Bang singularity in between. ]]></content:encoded> <dc:title>An Infinitely Old Universe with Planck Fields Before and After the Big Bang</dc:title> <dc:creator>Dragana Pilipovi膰</dc:creator> <dc:identifier>doi: 10.3390/universe10100400</dc:identifier> <dc:source>Universe</dc:source> <dc:date>2024-10-17</dc:date> <prism:publicationName>Universe</prism:publicationName> <prism:publicationDate>2024-10-17</prism:publicationDate> <prism:volume>10</prism:volume> <prism:number>10</prism:number> <prism:section>Article</prism:section> <prism:startingPage>400</prism:startingPage> <prism:doi>10.3390/universe10100400</prism:doi> <prism:url>https://www.mdpi.com/2218-1997/10/10/400</prism:url> <cc:license rdf:resource="CC BY 4.0"/> </item> <item rdf:about="https://www.mdpi.com/2218-1997/10/10/399"> <title>Universe, Vol. 10, Pages 399: Neutral-Current Single &pi;0 Production on Argon</title> <link>https://www.mdpi.com/2218-1997/10/10/399</link> <description>We interpret the recent MicroBooNE data on neutral-current single &amp;pi;0 production on argon with the hypothesis that this process occurs via Delta excitation. We calculate the flux-integrated total cross section with our RPA-based model which allows for a simultaneous description of Delta-mediated resonant and coherent pion production. We also discuss the ratio between the two exclusive measurements with one proton and zero protons in the final state.</description> <pubDate>2024-10-16</pubDate> <content:encoded><![CDATA[ Universe, Vol. 10, Pages 399: Neutral-Current Single &pi;0 Production on Argon Universe <a href="https://www.mdpi.com/2218-1997/10/10/399">doi: 10.3390/universe10100399</a> Authors: Marco Martini Magda Ericson Guy Chanfray We interpret the recent MicroBooNE data on neutral-current single &amp;pi;0 production on argon with the hypothesis that this process occurs via Delta excitation. We calculate the flux-integrated total cross section with our RPA-based model which allows for a simultaneous description of Delta-mediated resonant and coherent pion production. We also discuss the ratio between the two exclusive measurements with one proton and zero protons in the final state. ]]></content:encoded> <dc:title>Neutral-Current Single &amp;pi;0 Production on Argon</dc:title> <dc:creator>Marco Martini</dc:creator> <dc:creator>Magda Ericson</dc:creator> <dc:creator>Guy Chanfray</dc:creator> <dc:identifier>doi: 10.3390/universe10100399</dc:identifier> <dc:source>Universe</dc:source> <dc:date>2024-10-16</dc:date> <prism:publicationName>Universe</prism:publicationName> <prism:publicationDate>2024-10-16</prism:publicationDate> <prism:volume>10</prism:volume> <prism:number>10</prism:number> <prism:section>Article</prism:section> <prism:startingPage>399</prism:startingPage> <prism:doi>10.3390/universe10100399</prism:doi> <prism:url>https://www.mdpi.com/2218-1997/10/10/399</prism:url> <cc:license rdf:resource="CC BY 4.0"/> </item> <item rdf:about="https://www.mdpi.com/2218-1997/10/10/398"> <title>Universe, Vol. 10, Pages 398: Time-Delay Interferometry: The Key Technique in Data Pre-Processing Analysis of Space-Based Gravitational Waves</title> <link>https://www.mdpi.com/2218-1997/10/10/398</link> <description>Space gravitational wave detection primarily focuses on the rich wave sources corresponding to the millihertz frequency band, which provide key information for studying the fundamental physics of cosmology and astrophysics. However, gravitational wave signals are extremely weak, and any noise during the detection process could potentially overwhelm the gravitational wave signals. Therefore, data pre-processing is necessary to suppress the main noise sources. Among the various noise sources, laser phase noise is dominant, approximately seven orders of magnitude larger in strength than typical gravitational wave signals, and requires suppression using time-delay interferometry (TDI) techniques, which involve combining raw data with time delays. This paper will be based on the basic principles of TDI to present methods for obtaining multi-type TDI combinations, including algebraic methods for solving indeterminate equations and geometric methods for symbolic search. Furthermore, the applicability of TDI under actual operating conditions will be considered, such as the arm locking in conjunction with the TDI algorithm. Finally, the sensitivity functions for different types of TDI combinations will be provided, which can be used to evaluate the signal-to-noise ratio (SNRs) of different TDI combinations.</description> <pubDate>2024-10-16</pubDate> <content:encoded><![CDATA[ Universe, Vol. 10, Pages 398: Time-Delay Interferometry: The Key Technique in Data Pre-Processing Analysis of Space-Based Gravitational Waves Universe <a href="https://www.mdpi.com/2218-1997/10/10/398">doi: 10.3390/universe10100398</a> Authors: Pan-Pan Wang Cheng-Gang Shao Space gravitational wave detection primarily focuses on the rich wave sources corresponding to the millihertz frequency band, which provide key information for studying the fundamental physics of cosmology and astrophysics. However, gravitational wave signals are extremely weak, and any noise during the detection process could potentially overwhelm the gravitational wave signals. Therefore, data pre-processing is necessary to suppress the main noise sources. Among the various noise sources, laser phase noise is dominant, approximately seven orders of magnitude larger in strength than typical gravitational wave signals, and requires suppression using time-delay interferometry (TDI) techniques, which involve combining raw data with time delays. This paper will be based on the basic principles of TDI to present methods for obtaining multi-type TDI combinations, including algebraic methods for solving indeterminate equations and geometric methods for symbolic search. Furthermore, the applicability of TDI under actual operating conditions will be considered, such as the arm locking in conjunction with the TDI algorithm. Finally, the sensitivity functions for different types of TDI combinations will be provided, which can be used to evaluate the signal-to-noise ratio (SNRs) of different TDI combinations. ]]></content:encoded> <dc:title>Time-Delay Interferometry: The Key Technique in Data Pre-Processing Analysis of Space-Based Gravitational Waves</dc:title> <dc:creator>Pan-Pan Wang</dc:creator> <dc:creator>Cheng-Gang Shao</dc:creator> <dc:identifier>doi: 10.3390/universe10100398</dc:identifier> <dc:source>Universe</dc:source> <dc:date>2024-10-16</dc:date> <prism:publicationName>Universe</prism:publicationName> <prism:publicationDate>2024-10-16</prism:publicationDate> <prism:volume>10</prism:volume> <prism:number>10</prism:number> <prism:section>Review</prism:section> <prism:startingPage>398</prism:startingPage> <prism:doi>10.3390/universe10100398</prism:doi> <prism:url>https://www.mdpi.com/2218-1997/10/10/398</prism:url> <cc:license rdf:resource="CC BY 4.0"/> </item> <item rdf:about="https://www.mdpi.com/2218-1997/10/10/397"> <title>Universe, Vol. 10, Pages 397: Universal Properties of the Evolution of the Universe in Modified Loop Quantum Cosmology</title> <link>https://www.mdpi.com/2218-1997/10/10/397</link> <description>In this paper, we systematically study the evolution of the Universe within the framework of a modified loop quantum cosmological model (mLQC-I) using various inflationary potentials, including chaotic, Starobinsky, generalized Starobinsky, polynomials of the first and second kinds, generalized T-models and natural inflation. In all these models, the big bang singularity is replaced by a quantum bounce, and the evolution of the Universe, both before and after the bounce, is universal and weakly dependent on the inflationary potentials, as long as the evolution is dominated by the kinetic energy of the inflaton at the bounce. In particular, the pre-bounce evolution can be universally divided into three different phases: pre-bouncing, pre-transition, and pre-de Sitter. The pre-bouncing phase occurs immediately before the quantum bounce, during which the evolution of the Universe is dominated by the kinetic energy of the inflaton. Thus, the equation of state of the inflaton is about one, w(&amp;#981;)&amp;#8771;1. Soon, the inflation potential takes over, so w(&amp;#981;) rapidly falls from one to negative one. This pre-transition phase is very short and quickly turns into the pre-de Sitter phase, whereby the effective cosmological constant of Planck size takes over and dominates the rest of the contracting phase. Throughout the entire pre-bounce regime, the evolution of both the expansion factor and the inflaton can be approximated by universal analytical solutions, independent of the specific inflation potentials.</description> <pubDate>2024-10-15</pubDate> <content:encoded><![CDATA[ Universe, Vol. 10, Pages 397: Universal Properties of the Evolution of the Universe in Modified Loop Quantum Cosmology Universe <a href="https://www.mdpi.com/2218-1997/10/10/397">doi: 10.3390/universe10100397</a> Authors: Jamal Saeed Rui Pan Christian Brown Gerald Cleaver Anzhong Wang In this paper, we systematically study the evolution of the Universe within the framework of a modified loop quantum cosmological model (mLQC-I) using various inflationary potentials, including chaotic, Starobinsky, generalized Starobinsky, polynomials of the first and second kinds, generalized T-models and natural inflation. In all these models, the big bang singularity is replaced by a quantum bounce, and the evolution of the Universe, both before and after the bounce, is universal and weakly dependent on the inflationary potentials, as long as the evolution is dominated by the kinetic energy of the inflaton at the bounce. In particular, the pre-bounce evolution can be universally divided into three different phases: pre-bouncing, pre-transition, and pre-de Sitter. The pre-bouncing phase occurs immediately before the quantum bounce, during which the evolution of the Universe is dominated by the kinetic energy of the inflaton. Thus, the equation of state of the inflaton is about one, w(&amp;#981;)&amp;#8771;1. Soon, the inflation potential takes over, so w(&amp;#981;) rapidly falls from one to negative one. This pre-transition phase is very short and quickly turns into the pre-de Sitter phase, whereby the effective cosmological constant of Planck size takes over and dominates the rest of the contracting phase. Throughout the entire pre-bounce regime, the evolution of both the expansion factor and the inflaton can be approximated by universal analytical solutions, independent of the specific inflation potentials. ]]></content:encoded> <dc:title>Universal Properties of the Evolution of the Universe in Modified Loop Quantum Cosmology</dc:title> <dc:creator>Jamal Saeed</dc:creator> <dc:creator>Rui Pan</dc:creator> <dc:creator>Christian Brown</dc:creator> <dc:creator>Gerald Cleaver</dc:creator> <dc:creator>Anzhong Wang</dc:creator> <dc:identifier>doi: 10.3390/universe10100397</dc:identifier> <dc:source>Universe</dc:source> <dc:date>2024-10-15</dc:date> <prism:publicationName>Universe</prism:publicationName> <prism:publicationDate>2024-10-15</prism:publicationDate> <prism:volume>10</prism:volume> <prism:number>10</prism:number> <prism:section>Article</prism:section> <prism:startingPage>397</prism:startingPage> <prism:doi>10.3390/universe10100397</prism:doi> <prism:url>https://www.mdpi.com/2218-1997/10/10/397</prism:url> <cc:license rdf:resource="CC BY 4.0"/> </item> <item rdf:about="https://www.mdpi.com/2218-1997/10/10/396"> <title>Universe, Vol. 10, Pages 396: Introduction to Bell&rsquo;s Inequality in Quantum Mechanics</title> <link>https://www.mdpi.com/2218-1997/10/10/396</link> <description>A pedagogical introduction to Bell&amp;rsquo;s inequality in Quantum Mechanics is presented. Several examples, ranging from spin 1/2 to coherent and squeezed states are worked out. The generalization to Mermin&amp;rsquo;s inequalities and to GHZ states is also outlined.</description> <pubDate>2024-10-15</pubDate> <content:encoded><![CDATA[ Universe, Vol. 10, Pages 396: Introduction to Bell&rsquo;s Inequality in Quantum Mechanics Universe <a href="https://www.mdpi.com/2218-1997/10/10/396">doi: 10.3390/universe10100396</a> Authors: Marcelo Santos Guimaraes Itzhak Roditi Silvio Paolo Sorella A pedagogical introduction to Bell&amp;rsquo;s inequality in Quantum Mechanics is presented. Several examples, ranging from spin 1/2 to coherent and squeezed states are worked out. The generalization to Mermin&amp;rsquo;s inequalities and to GHZ states is also outlined. ]]></content:encoded> <dc:title>Introduction to Bell&amp;rsquo;s Inequality in Quantum Mechanics</dc:title> <dc:creator>Marcelo Santos Guimaraes</dc:creator> <dc:creator>Itzhak Roditi</dc:creator> <dc:creator>Silvio Paolo Sorella</dc:creator> <dc:identifier>doi: 10.3390/universe10100396</dc:identifier> <dc:source>Universe</dc:source> <dc:date>2024-10-15</dc:date> <prism:publicationName>Universe</prism:publicationName> <prism:publicationDate>2024-10-15</prism:publicationDate> <prism:volume>10</prism:volume> <prism:number>10</prism:number> <prism:section>Tutorial</prism:section> <prism:startingPage>396</prism:startingPage> <prism:doi>10.3390/universe10100396</prism:doi> <prism:url>https://www.mdpi.com/2218-1997/10/10/396</prism:url> <cc:license rdf:resource="CC BY 4.0"/> </item> <item rdf:about="https://www.mdpi.com/2218-1997/10/10/395"> <title>Universe, Vol. 10, Pages 395: Photometry and Models of Seven Main-Belt Asteroids</title> <link>https://www.mdpi.com/2218-1997/10/10/395</link> <description>The China Near-Earth Object Survey Telescope (CNEOST) conducted four photometric surveys from 2015 to 2018 using image processing and aperture photometry techniques to obtain extensive light curve data on asteroids. The second-order Fourier series method was selected for its efficiency in determining the rotation periods of the observed asteroids. Our study successfully derived rotation periods for 892 asteroids, with 648 of those matching values recorded in the LCDB (for asteroids with U &amp;gt; 2). To enhance the reliability of the derived spin parameters and shape models, we also amassed a comprehensive collection of published light curve data supplemented by additional photometric observations on a targeted subset of asteroids conducted using multiple telescopes between 2021 and 2022. Through the application of convex inversion techniques, we successfully derived spin parameters and shape models for seven main-belt asteroids (MBAs): (2233) Kuznetsov, (2294) Andronikov, (2253) Espinette, (4796) Lewis, (1563) Noel, (2912) Lapalma, and (5150) Fellini. Our thorough analysis identified two credible orientations for the rotational poles of these MBAs, shedding light on the prevalent issue of &amp;ldquo;ambiguity in pole direction&amp;rdquo; that often accompanies photometric inversion processes. CNEOST continues its observational endeavors, and future collected data combined with other independent photometric measurements will facilitate further inversion to better constrain the spin parameters and yield more refined shape models.</description> <pubDate>2024-10-14</pubDate> <content:encoded><![CDATA[ Universe, Vol. 10, Pages 395: Photometry and Models of Seven Main-Belt Asteroids Universe <a href="https://www.mdpi.com/2218-1997/10/10/395">doi: 10.3390/universe10100395</a> Authors: Jun Tian Haibin Zhao Bin Li Yongxiong Zhang Jian Chen Leonid Elenin Xiaoping Lu The China Near-Earth Object Survey Telescope (CNEOST) conducted four photometric surveys from 2015 to 2018 using image processing and aperture photometry techniques to obtain extensive light curve data on asteroids. The second-order Fourier series method was selected for its efficiency in determining the rotation periods of the observed asteroids. Our study successfully derived rotation periods for 892 asteroids, with 648 of those matching values recorded in the LCDB (for asteroids with U &amp;gt; 2). To enhance the reliability of the derived spin parameters and shape models, we also amassed a comprehensive collection of published light curve data supplemented by additional photometric observations on a targeted subset of asteroids conducted using multiple telescopes between 2021 and 2022. Through the application of convex inversion techniques, we successfully derived spin parameters and shape models for seven main-belt asteroids (MBAs): (2233) Kuznetsov, (2294) Andronikov, (2253) Espinette, (4796) Lewis, (1563) Noel, (2912) Lapalma, and (5150) Fellini. Our thorough analysis identified two credible orientations for the rotational poles of these MBAs, shedding light on the prevalent issue of &amp;ldquo;ambiguity in pole direction&amp;rdquo; that often accompanies photometric inversion processes. CNEOST continues its observational endeavors, and future collected data combined with other independent photometric measurements will facilitate further inversion to better constrain the spin parameters and yield more refined shape models. ]]></content:encoded> <dc:title>Photometry and Models of Seven Main-Belt Asteroids</dc:title> <dc:creator>Jun Tian</dc:creator> <dc:creator>Haibin Zhao</dc:creator> <dc:creator>Bin Li</dc:creator> <dc:creator>Yongxiong Zhang</dc:creator> <dc:creator>Jian Chen</dc:creator> <dc:creator>Leonid Elenin</dc:creator> <dc:creator>Xiaoping Lu</dc:creator> <dc:identifier>doi: 10.3390/universe10100395</dc:identifier> <dc:source>Universe</dc:source> <dc:date>2024-10-14</dc:date> <prism:publicationName>Universe</prism:publicationName> <prism:publicationDate>2024-10-14</prism:publicationDate> <prism:volume>10</prism:volume> <prism:number>10</prism:number> <prism:section>Article</prism:section> <prism:startingPage>395</prism:startingPage> <prism:doi>10.3390/universe10100395</prism:doi> <prism:url>https://www.mdpi.com/2218-1997/10/10/395</prism:url> <cc:license rdf:resource="CC BY 4.0"/> </item> <item rdf:about="https://www.mdpi.com/2218-1997/10/10/394"> <title>Universe, Vol. 10, Pages 394: Galaxy Classification Using EWGC</title> <link>https://www.mdpi.com/2218-1997/10/10/394</link> <description>The Enhanced Wide-field Galaxy Classification Network (EWGC) is a novel architecture designed to classify spiral and elliptical galaxies using Wide-field Infrared Survey Explorer (WISE) images. The EWGC achieves an impressive classification accuracy of 90.02%, significantly outperforming the previously developed WGC network and underscoring its superior performance in galaxy morphology classification. Remarkably, the network demonstrates a consistent accuracy of 90.02% when processing both multi-target and single-target images. Such robustness indicates the EWGC&amp;rsquo;s versatility and potential for various applications in galaxy classification tasks.</description> <pubDate>2024-10-12</pubDate> <content:encoded><![CDATA[ Universe, Vol. 10, Pages 394: Galaxy Classification Using EWGC Universe <a href="https://www.mdpi.com/2218-1997/10/10/394">doi: 10.3390/universe10100394</a> Authors: Yunyan Nie Zhiren Pan Jianwei Zhou Bo Qiu A-Li Luo Chong Luo Xiaodong Luan The Enhanced Wide-field Galaxy Classification Network (EWGC) is a novel architecture designed to classify spiral and elliptical galaxies using Wide-field Infrared Survey Explorer (WISE) images. The EWGC achieves an impressive classification accuracy of 90.02%, significantly outperforming the previously developed WGC network and underscoring its superior performance in galaxy morphology classification. Remarkably, the network demonstrates a consistent accuracy of 90.02% when processing both multi-target and single-target images. Such robustness indicates the EWGC&amp;rsquo;s versatility and potential for various applications in galaxy classification tasks. ]]></content:encoded> <dc:title>Galaxy Classification Using EWGC</dc:title> <dc:creator>Yunyan Nie</dc:creator> <dc:creator>Zhiren Pan</dc:creator> <dc:creator>Jianwei Zhou</dc:creator> <dc:creator>Bo Qiu</dc:creator> <dc:creator>A-Li Luo</dc:creator> <dc:creator>Chong Luo</dc:creator> <dc:creator>Xiaodong Luan</dc:creator> <dc:identifier>doi: 10.3390/universe10100394</dc:identifier> <dc:source>Universe</dc:source> <dc:date>2024-10-12</dc:date> <prism:publicationName>Universe</prism:publicationName> <prism:publicationDate>2024-10-12</prism:publicationDate> <prism:volume>10</prism:volume> <prism:number>10</prism:number> <prism:section>Article</prism:section> <prism:startingPage>394</prism:startingPage> <prism:doi>10.3390/universe10100394</prism:doi> <prism:url>https://www.mdpi.com/2218-1997/10/10/394</prism:url> <cc:license rdf:resource="CC BY 4.0"/> </item> <item rdf:about="https://www.mdpi.com/2218-1997/10/10/393"> <title>Universe, Vol. 10, Pages 393: Decoding Quantum Gravity Information with Black Hole Accretion Disk</title> <link>https://www.mdpi.com/2218-1997/10/10/393</link> <description>Integrating loop quantum gravity with classical gravitational collapse models offers an effective solution to the black hole singularity problem and predicts the formation of a white hole in the later stages of collapse. Furthermore, the quantum extension of Kruskal spacetime indicates that white holes may convey information about earlier companion black holes. Photons emitted from the accretion disks of these companion black holes enter the black hole, traverse the highly quantum region, and then re-emerge from white holes in our universe. This process enables us to observe images of the companion black holes&amp;rsquo; accretion disks, providing insights into quantum gravity. In our study, we successfully obtained these accretion disk images. Our results indicate that these accretion disk images are confined within a circle with a radius equal to the critical impact parameter, while traditional accretion disk images are typically located outside this circle. As the observational angle increases, the accretion disk images transition from a ring shape to a shell-like shape. Furthermore, the positional and width characteristics of these accretion disk images are opposite to those of traditional accretion disk images. These findings provide valuable references for astronomical observations aimed at validating the investigated quantum gravity model.</description> <pubDate>2024-10-11</pubDate> <content:encoded><![CDATA[ Universe, Vol. 10, Pages 393: Decoding Quantum Gravity Information with Black Hole Accretion Disk Universe <a href="https://www.mdpi.com/2218-1997/10/10/393">doi: 10.3390/universe10100393</a> Authors: Lei You Yu-Hang Feng Rui-Bo Wang Xian-Ru Hu Jian-Bo Deng Integrating loop quantum gravity with classical gravitational collapse models offers an effective solution to the black hole singularity problem and predicts the formation of a white hole in the later stages of collapse. Furthermore, the quantum extension of Kruskal spacetime indicates that white holes may convey information about earlier companion black holes. Photons emitted from the accretion disks of these companion black holes enter the black hole, traverse the highly quantum region, and then re-emerge from white holes in our universe. This process enables us to observe images of the companion black holes&amp;rsquo; accretion disks, providing insights into quantum gravity. In our study, we successfully obtained these accretion disk images. Our results indicate that these accretion disk images are confined within a circle with a radius equal to the critical impact parameter, while traditional accretion disk images are typically located outside this circle. As the observational angle increases, the accretion disk images transition from a ring shape to a shell-like shape. Furthermore, the positional and width characteristics of these accretion disk images are opposite to those of traditional accretion disk images. These findings provide valuable references for astronomical observations aimed at validating the investigated quantum gravity model. ]]></content:encoded> <dc:title>Decoding Quantum Gravity Information with Black Hole Accretion Disk</dc:title> <dc:creator>Lei You</dc:creator> <dc:creator>Yu-Hang Feng</dc:creator> <dc:creator>Rui-Bo Wang</dc:creator> <dc:creator>Xian-Ru Hu</dc:creator> <dc:creator>Jian-Bo Deng</dc:creator> <dc:identifier>doi: 10.3390/universe10100393</dc:identifier> <dc:source>Universe</dc:source> <dc:date>2024-10-11</dc:date> <prism:publicationName>Universe</prism:publicationName> <prism:publicationDate>2024-10-11</prism:publicationDate> <prism:volume>10</prism:volume> <prism:number>10</prism:number> <prism:section>Article</prism:section> <prism:startingPage>393</prism:startingPage> <prism:doi>10.3390/universe10100393</prism:doi> <prism:url>https://www.mdpi.com/2218-1997/10/10/393</prism:url> <cc:license rdf:resource="CC BY 4.0"/> </item> <item rdf:about="https://www.mdpi.com/2218-1997/10/10/392"> <title>Universe, Vol. 10, Pages 392: Searching for Hadronic Signatures in the Time Domain of Blazar Emission: The Case of Mrk 501</title> <link>https://www.mdpi.com/2218-1997/10/10/392</link> <description>Blazars&amp;mdash;a subclass of active galaxies&amp;mdash;are intrinsically time-variable broadband sources of electromagnetic radiation. In this contribution, we explored relativistic proton (hadronic) signatures in the time domain blazar emission and searched for those parameter combinations that unveil their presence during flaring epochs. We generated time series for key model parameters, like magnetic field strength and the power-law index of radiating particles, which were motivated from a simulated time series with statistical properties describing the observed GeV gamma-ray flux. We chose the TeV blazar Mrk 501 as our test case, as it had been the study ground for extensive investigations during individual flaring events. Using the code LeHaMoC, we computed the electromagnetic and neutrino emissions for a period of several years that contained several flares of interest. We show that for both of those particle distributions the power-law index variations that were tied to moderate changes in the magnetic field strength of the emitting region might naturally lead to hard X-ray flares with very-high-energy &amp;gamma;-ray counterparts. We found spectral differences measurable by the Cherenkov Telescope Array Observatory at sub-TeV energies, and we computed the neutrino fluence over 14.5 years. The latter predicted &amp;sim;0.2 muon and anti-muon neutrinos, consistent with the non-detection of high-energy neutrinos from Mrk 501.</description> <pubDate>2024-10-10</pubDate> <content:encoded><![CDATA[ Universe, Vol. 10, Pages 392: Searching for Hadronic Signatures in the Time Domain of Blazar Emission: The Case of Mrk 501 Universe <a href="https://www.mdpi.com/2218-1997/10/10/392">doi: 10.3390/universe10100392</a> Authors: Margaritis Chatzis Stamatios I. Stathopoulos Maria Petropoulou Georgios Vasilopoulos Blazars&amp;mdash;a subclass of active galaxies&amp;mdash;are intrinsically time-variable broadband sources of electromagnetic radiation. In this contribution, we explored relativistic proton (hadronic) signatures in the time domain blazar emission and searched for those parameter combinations that unveil their presence during flaring epochs. We generated time series for key model parameters, like magnetic field strength and the power-law index of radiating particles, which were motivated from a simulated time series with statistical properties describing the observed GeV gamma-ray flux. We chose the TeV blazar Mrk 501 as our test case, as it had been the study ground for extensive investigations during individual flaring events. Using the code LeHaMoC, we computed the electromagnetic and neutrino emissions for a period of several years that contained several flares of interest. We show that for both of those particle distributions the power-law index variations that were tied to moderate changes in the magnetic field strength of the emitting region might naturally lead to hard X-ray flares with very-high-energy &amp;gamma;-ray counterparts. We found spectral differences measurable by the Cherenkov Telescope Array Observatory at sub-TeV energies, and we computed the neutrino fluence over 14.5 years. The latter predicted &amp;sim;0.2 muon and anti-muon neutrinos, consistent with the non-detection of high-energy neutrinos from Mrk 501. ]]></content:encoded> <dc:title>Searching for Hadronic Signatures in the Time Domain of Blazar Emission: The Case of Mrk 501</dc:title> <dc:creator>Margaritis Chatzis</dc:creator> <dc:creator>Stamatios I. Stathopoulos</dc:creator> <dc:creator>Maria Petropoulou</dc:creator> <dc:creator>Georgios Vasilopoulos</dc:creator> <dc:identifier>doi: 10.3390/universe10100392</dc:identifier> <dc:source>Universe</dc:source> <dc:date>2024-10-10</dc:date> <prism:publicationName>Universe</prism:publicationName> <prism:publicationDate>2024-10-10</prism:publicationDate> <prism:volume>10</prism:volume> <prism:number>10</prism:number> <prism:section>Article</prism:section> <prism:startingPage>392</prism:startingPage> <prism:doi>10.3390/universe10100392</prism:doi> <prism:url>https://www.mdpi.com/2218-1997/10/10/392</prism:url> <cc:license rdf:resource="CC BY 4.0"/> </item> <item rdf:about="https://www.mdpi.com/2218-1997/10/10/391"> <title>Universe, Vol. 10, Pages 391: The Mother&rsquo;s Day Solar Storm of 11 May 2024 and Its Effect on Earth&rsquo;s Radiation Belts</title> <link>https://www.mdpi.com/2218-1997/10/10/391</link> <description>The month of May 2024 was characterized by solar energetic particles events directed towards the Earth, especially the big event causing a strong terrestrial geomagnetic storm during the night from 10 to 11 May 2024, with auroras observed everywhere in Europe. This was the strongest storm for the last 20 years with a Disturbed Storm Time index Dst &amp;lt; &amp;minus;400 nT. In the present work, we show with observations of GOES, PROBA-V/EPT and MetOP/MEPED that this exceptional event was associated with the injection of energetic protons in the proton radiation belt, with important consequences for the South part of the South Atlantic Anomaly (SAA). In addition, the geomagnetic storm caused by the solar eruption has had tremendous impacts on the electron radiation belts. Indeed, we show that for 0.3 to 1 MeV electrons, the storm led to a long lasting four belts configuration which was not observed before with EPT launched in 2013, until a smaller geomagnetic storm took place at the end of June 2024. Moreover, for the first time since its launch, observations of the EPT show that ultra-relativistic electrons with E&amp;gt;2 MeV have been injected into the inner belt down to McIlwain parameter L = 2.4, violating the impenetrable barrier previously estimated to be located at L = 2.8.</description> <pubDate>2024-10-10</pubDate> <content:encoded><![CDATA[ Universe, Vol. 10, Pages 391: The Mother&rsquo;s Day Solar Storm of 11 May 2024 and Its Effect on Earth&rsquo;s Radiation Belts Universe <a href="https://www.mdpi.com/2218-1997/10/10/391">doi: 10.3390/universe10100391</a> Authors: Viviane Pierrard Alexandre Winant Edith Botek Maximilien P茅ters de Bonhome The month of May 2024 was characterized by solar energetic particles events directed towards the Earth, especially the big event causing a strong terrestrial geomagnetic storm during the night from 10 to 11 May 2024, with auroras observed everywhere in Europe. This was the strongest storm for the last 20 years with a Disturbed Storm Time index Dst &amp;lt; &amp;minus;400 nT. In the present work, we show with observations of GOES, PROBA-V/EPT and MetOP/MEPED that this exceptional event was associated with the injection of energetic protons in the proton radiation belt, with important consequences for the South part of the South Atlantic Anomaly (SAA). In addition, the geomagnetic storm caused by the solar eruption has had tremendous impacts on the electron radiation belts. Indeed, we show that for 0.3 to 1 MeV electrons, the storm led to a long lasting four belts configuration which was not observed before with EPT launched in 2013, until a smaller geomagnetic storm took place at the end of June 2024. Moreover, for the first time since its launch, observations of the EPT show that ultra-relativistic electrons with E&amp;gt;2 MeV have been injected into the inner belt down to McIlwain parameter L = 2.4, violating the impenetrable barrier previously estimated to be located at L = 2.8. ]]></content:encoded> <dc:title>The Mother&amp;rsquo;s Day Solar Storm of 11 May 2024 and Its Effect on Earth&amp;rsquo;s Radiation Belts</dc:title> <dc:creator>Viviane Pierrard</dc:creator> <dc:creator>Alexandre Winant</dc:creator> <dc:creator>Edith Botek</dc:creator> <dc:creator>Maximilien P茅ters de Bonhome</dc:creator> <dc:identifier>doi: 10.3390/universe10100391</dc:identifier> <dc:source>Universe</dc:source> <dc:date>2024-10-10</dc:date> <prism:publicationName>Universe</prism:publicationName> <prism:publicationDate>2024-10-10</prism:publicationDate> <prism:volume>10</prism:volume> <prism:number>10</prism:number> <prism:section>Article</prism:section> <prism:startingPage>391</prism:startingPage> <prism:doi>10.3390/universe10100391</prism:doi> <prism:url>https://www.mdpi.com/2218-1997/10/10/391</prism:url> <cc:license rdf:resource="CC BY 4.0"/> </item> <item rdf:about="https://www.mdpi.com/2218-1997/10/10/390"> <title>Universe, Vol. 10, Pages 390: Prigogine&rsquo;s Second Law and Determination of the EUP and GUP Parameters in Small Black Hole Thermodynamics</title> <link>https://www.mdpi.com/2218-1997/10/10/390</link> <description>In 1974, Stephen Hawking made the groundbreaking discovery that black holes emit thermal radiation, characterized by a specific temperature now known as the Hawking temperature. While his original derivation is intricate, retrieving the exact expressions for black hole temperature and entropy in a simpler, more intuitive way without losing the core physical principles behind Hawking&amp;rsquo;s assumptions is possible. This is obtained by employing the Heisenberg Uncertainty Principle, which is known to be connected to thenvacuum fluctuation. This exercise allows us to easily perform more complex calculations involving the effects of quantum gravity. This work aims to answer the following question: Is it possible to reconcile Prigogine&amp;rsquo;s second law of thermodynamics for open systems and the second law of black hole dynamics with Hawking radiation? Due to quantum gravity effects, the Heisenberg Uncertainty Principle has been extended to the Generalized Uncertainty Principle (GUP) and successively to the Extended Uncertainty Principle (EUP). The expression for the EUP parameter is obtained by conjecturing that Prigogine&amp;rsquo;s second law of thermodynamics and the second law of black holes are not violated by the Hawking thermal radiation mechanism. The modified expression for the entropy of a Schwarzschild black hole is also derived.</description> <pubDate>2024-10-07</pubDate> <content:encoded><![CDATA[ Universe, Vol. 10, Pages 390: Prigogine&rsquo;s Second Law and Determination of the EUP and GUP Parameters in Small Black Hole Thermodynamics Universe <a href="https://www.mdpi.com/2218-1997/10/10/390">doi: 10.3390/universe10100390</a> Authors: Giorgio Sonnino In 1974, Stephen Hawking made the groundbreaking discovery that black holes emit thermal radiation, characterized by a specific temperature now known as the Hawking temperature. While his original derivation is intricate, retrieving the exact expressions for black hole temperature and entropy in a simpler, more intuitive way without losing the core physical principles behind Hawking&amp;rsquo;s assumptions is possible. This is obtained by employing the Heisenberg Uncertainty Principle, which is known to be connected to thenvacuum fluctuation. This exercise allows us to easily perform more complex calculations involving the effects of quantum gravity. This work aims to answer the following question: Is it possible to reconcile Prigogine&amp;rsquo;s second law of thermodynamics for open systems and the second law of black hole dynamics with Hawking radiation? Due to quantum gravity effects, the Heisenberg Uncertainty Principle has been extended to the Generalized Uncertainty Principle (GUP) and successively to the Extended Uncertainty Principle (EUP). The expression for the EUP parameter is obtained by conjecturing that Prigogine&amp;rsquo;s second law of thermodynamics and the second law of black holes are not violated by the Hawking thermal radiation mechanism. The modified expression for the entropy of a Schwarzschild black hole is also derived. ]]></content:encoded> <dc:title>Prigogine&amp;rsquo;s Second Law and Determination of the EUP and GUP Parameters in Small Black Hole Thermodynamics</dc:title> <dc:creator>Giorgio Sonnino</dc:creator> <dc:identifier>doi: 10.3390/universe10100390</dc:identifier> <dc:source>Universe</dc:source> <dc:date>2024-10-07</dc:date> <prism:publicationName>Universe</prism:publicationName> <prism:publicationDate>2024-10-07</prism:publicationDate> <prism:volume>10</prism:volume> <prism:number>10</prism:number> <prism:section>Article</prism:section> <prism:startingPage>390</prism:startingPage> <prism:doi>10.3390/universe10100390</prism:doi> <prism:url>https://www.mdpi.com/2218-1997/10/10/390</prism:url> <cc:license rdf:resource="CC BY 4.0"/> </item> <item rdf:about="https://www.mdpi.com/2218-1997/10/10/389"> <title>Universe, Vol. 10, Pages 389: Spinning Systems in Quantum Mechanics: An Overview and New Trends</title> <link>https://www.mdpi.com/2218-1997/10/10/389</link> <description>The study of spinning systems plays a question of interest in several research branches in physics. It allows the understanding of simple classical mechanical systems but also provides us with tools to investigate a wide range of phenomena, from condensed matter physics to gravitation and cosmology. In this contribution, we review some remarkable theoretical aspects involving the description of spinning quantum systems. We explore the nonrelativistic and relativistic domains and their respective applications in fields such as graphene physics and topological defects in gravitation.</description> <pubDate>2024-10-04</pubDate> <content:encoded><![CDATA[ Universe, Vol. 10, Pages 389: Spinning Systems in Quantum Mechanics: An Overview and New Trends Universe <a href="https://www.mdpi.com/2218-1997/10/10/389">doi: 10.3390/universe10100389</a> Authors: E. Brito J煤lio E. Brand茫o M谩rcio M. Cunha The study of spinning systems plays a question of interest in several research branches in physics. It allows the understanding of simple classical mechanical systems but also provides us with tools to investigate a wide range of phenomena, from condensed matter physics to gravitation and cosmology. In this contribution, we review some remarkable theoretical aspects involving the description of spinning quantum systems. We explore the nonrelativistic and relativistic domains and their respective applications in fields such as graphene physics and topological defects in gravitation. ]]></content:encoded> <dc:title>Spinning Systems in Quantum Mechanics: An Overview and New Trends</dc:title> <dc:creator>E. Brito</dc:creator> <dc:creator>J煤lio E. Brand茫o</dc:creator> <dc:creator>M谩rcio M. Cunha</dc:creator> <dc:identifier>doi: 10.3390/universe10100389</dc:identifier> <dc:source>Universe</dc:source> <dc:date>2024-10-04</dc:date> <prism:publicationName>Universe</prism:publicationName> <prism:publicationDate>2024-10-04</prism:publicationDate> <prism:volume>10</prism:volume> <prism:number>10</prism:number> <prism:section>Review</prism:section> <prism:startingPage>389</prism:startingPage> <prism:doi>10.3390/universe10100389</prism:doi> <prism:url>https://www.mdpi.com/2218-1997/10/10/389</prism:url> <cc:license rdf:resource="CC BY 4.0"/> </item> <item rdf:about="https://www.mdpi.com/2218-1997/10/10/388"> <title>Universe, Vol. 10, Pages 388: Universes Emerging from Nothing and Disappearing into Nothing as an Endless Cosmological Process</title> <link>https://www.mdpi.com/2218-1997/10/10/388</link> <description>The equation of state of quantum fluctuations of the gravitational field of the universe depends on H4, where H is the Hubble constant. This means that it is invariant with respect to the Wick rotation, i.e., the transition from Lorentzian space-time to Euclidean space-time and vice versa. It is shown that the quantum birth of universes from Euclidean space-time, i.e., from nothing, and their quantum disappearance to nothing (return to Euclidean space-time) by the time the density of the matter filling the universe becomes negligible could be a likely cosmological scenario. On an infinite time axis, this is an endless process of birth and death of universes appearing and disappearing and replacing each other. Within this scenario, our current universe is going to disappear into nothing at z&amp;le;&amp;minus;0.68, i.e., after 18.37 billion years, and the lifetime of our universe and similar universes is about 32 billion years.</description> <pubDate>2024-10-03</pubDate> <content:encoded><![CDATA[ Universe, Vol. 10, Pages 388: Universes Emerging from Nothing and Disappearing into Nothing as an Endless Cosmological Process Universe <a href="https://www.mdpi.com/2218-1997/10/10/388">doi: 10.3390/universe10100388</a> Authors: Leonid Marochnik The equation of state of quantum fluctuations of the gravitational field of the universe depends on H4, where H is the Hubble constant. This means that it is invariant with respect to the Wick rotation, i.e., the transition from Lorentzian space-time to Euclidean space-time and vice versa. It is shown that the quantum birth of universes from Euclidean space-time, i.e., from nothing, and their quantum disappearance to nothing (return to Euclidean space-time) by the time the density of the matter filling the universe becomes negligible could be a likely cosmological scenario. On an infinite time axis, this is an endless process of birth and death of universes appearing and disappearing and replacing each other. Within this scenario, our current universe is going to disappear into nothing at z&amp;le;&amp;minus;0.68, i.e., after 18.37 billion years, and the lifetime of our universe and similar universes is about 32 billion years. ]]></content:encoded> <dc:title>Universes Emerging from Nothing and Disappearing into Nothing as an Endless Cosmological Process</dc:title> <dc:creator>Leonid Marochnik</dc:creator> <dc:identifier>doi: 10.3390/universe10100388</dc:identifier> <dc:source>Universe</dc:source> <dc:date>2024-10-03</dc:date> <prism:publicationName>Universe</prism:publicationName> <prism:publicationDate>2024-10-03</prism:publicationDate> <prism:volume>10</prism:volume> <prism:number>10</prism:number> <prism:section>Article</prism:section> <prism:startingPage>388</prism:startingPage> <prism:doi>10.3390/universe10100388</prism:doi> <prism:url>https://www.mdpi.com/2218-1997/10/10/388</prism:url> <cc:license rdf:resource="CC BY 4.0"/> </item> <item rdf:about="https://www.mdpi.com/2218-1997/10/10/387"> <title>Universe, Vol. 10, Pages 387: Exploring Neutrino Masses (g &minus; 2)&mu;,e in Type I+II Seesaw in Le&ndash;L&alpha;-Gauge Extended Model</title> <link>https://www.mdpi.com/2218-1997/10/10/387</link> <description>This paper aims to explore the implications of U(1)Le&amp;minus;L&amp;alpha; gauge symmetries, where &amp;alpha;=&amp;tau;,&amp;mu;, in the neutrino sector through type-(I+II) seesaw mechanisms. To achieve such a hybrid framework, we include a scalar triplet and three right-handed neutrinos. The model can successfully account for the active neutrino masses, mixing angles, mass squared differences, and the CP-violating phase within the 3&amp;sigma; bounds of NuFit v5.2 neutrino oscillation data. The presence of a new gauge boson at the MeV scale provides an explanation for the muon and electron (g&amp;minus;2) within the confines of their experimental limits. Furthermore, we scrutinize the proposed models in the context of upcoming long-baseline neutrino experiments such as DUNE, P2SO, T2HK, and T2HKK. The findings reveal that P2SO and T2HK have the ability to probe both models in their 5&amp;sigma;-allowed oscillation parameter region, whereas DUNE and T2HKK can conclusively test only the model with U(1)Le&amp;minus;L&amp;mu;-symmetry within the 5&amp;sigma; parameter space if the true values of the oscillation parameters remain consistent with NuFit v5.2.</description> <pubDate>2024-10-02</pubDate> <content:encoded><![CDATA[ Universe, Vol. 10, Pages 387: Exploring Neutrino Masses (g &minus; 2)&mu;,e in Type I+II Seesaw in Le&ndash;L&alpha;-Gauge Extended Model Universe <a href="https://www.mdpi.com/2218-1997/10/10/387">doi: 10.3390/universe10100387</a> Authors: Papia Panda Priya Mishra Mitesh Kumar Behera Shivaramakrishna Singirala Rukmani Mohanta This paper aims to explore the implications of U(1)Le&amp;minus;L&amp;alpha; gauge symmetries, where &amp;alpha;=&amp;tau;,&amp;mu;, in the neutrino sector through type-(I+II) seesaw mechanisms. To achieve such a hybrid framework, we include a scalar triplet and three right-handed neutrinos. The model can successfully account for the active neutrino masses, mixing angles, mass squared differences, and the CP-violating phase within the 3&amp;sigma; bounds of NuFit v5.2 neutrino oscillation data. The presence of a new gauge boson at the MeV scale provides an explanation for the muon and electron (g&amp;minus;2) within the confines of their experimental limits. Furthermore, we scrutinize the proposed models in the context of upcoming long-baseline neutrino experiments such as DUNE, P2SO, T2HK, and T2HKK. The findings reveal that P2SO and T2HK have the ability to probe both models in their 5&amp;sigma;-allowed oscillation parameter region, whereas DUNE and T2HKK can conclusively test only the model with U(1)Le&amp;minus;L&amp;mu;-symmetry within the 5&amp;sigma; parameter space if the true values of the oscillation parameters remain consistent with NuFit v5.2. ]]></content:encoded> <dc:title>Exploring Neutrino Masses (g &amp;minus; 2)&amp;mu;,e in Type I+II Seesaw in Le&amp;ndash;L&amp;alpha;-Gauge Extended Model</dc:title> <dc:creator>Papia Panda</dc:creator> <dc:creator>Priya Mishra</dc:creator> <dc:creator>Mitesh Kumar Behera</dc:creator> <dc:creator>Shivaramakrishna Singirala</dc:creator> <dc:creator>Rukmani Mohanta</dc:creator> <dc:identifier>doi: 10.3390/universe10100387</dc:identifier> <dc:source>Universe</dc:source> <dc:date>2024-10-02</dc:date> <prism:publicationName>Universe</prism:publicationName> <prism:publicationDate>2024-10-02</prism:publicationDate> <prism:volume>10</prism:volume> <prism:number>10</prism:number> <prism:section>Article</prism:section> <prism:startingPage>387</prism:startingPage> <prism:doi>10.3390/universe10100387</prism:doi> <prism:url>https://www.mdpi.com/2218-1997/10/10/387</prism:url> <cc:license rdf:resource="CC BY 4.0"/> </item> <item rdf:about="https://www.mdpi.com/2218-1997/10/10/386"> <title>Universe, Vol. 10, Pages 386: On Planetary Orbits, Ungravity and Entropic Gravity</title> <link>https://www.mdpi.com/2218-1997/10/10/386</link> <description>In previous works, entropic gravity and ungravity have been considered as possible solutions to the dark energy and dark matter problems. To test the viability of these models, modifications to planetary orbits are calculated for ungravity and different models of entropic gravity. Using the gravitational sector of unparticles, an equation for the contribution to the effect of orbital precession is obtained. We conclude that the estimated values for the ungravity parameters from planetary orbits are inconsistent with the values needed for the cosmological constant. The same ideas are explored for entropic gravity arising from a modified entropy&amp;ndash;area relationship.</description> <pubDate>2024-10-01</pubDate> <content:encoded><![CDATA[ Universe, Vol. 10, Pages 386: On Planetary Orbits, Ungravity and Entropic Gravity Universe <a href="https://www.mdpi.com/2218-1997/10/10/386">doi: 10.3390/universe10100386</a> Authors: Gemma P茅rez-Cu茅llar Miguel Sabido In previous works, entropic gravity and ungravity have been considered as possible solutions to the dark energy and dark matter problems. To test the viability of these models, modifications to planetary orbits are calculated for ungravity and different models of entropic gravity. Using the gravitational sector of unparticles, an equation for the contribution to the effect of orbital precession is obtained. We conclude that the estimated values for the ungravity parameters from planetary orbits are inconsistent with the values needed for the cosmological constant. The same ideas are explored for entropic gravity arising from a modified entropy&amp;ndash;area relationship. ]]></content:encoded> <dc:title>On Planetary Orbits, Ungravity and Entropic Gravity</dc:title> <dc:creator>Gemma P茅rez-Cu茅llar</dc:creator> <dc:creator>Miguel Sabido</dc:creator> <dc:identifier>doi: 10.3390/universe10100386</dc:identifier> <dc:source>Universe</dc:source> <dc:date>2024-10-01</dc:date> <prism:publicationName>Universe</prism:publicationName> <prism:publicationDate>2024-10-01</prism:publicationDate> <prism:volume>10</prism:volume> <prism:number>10</prism:number> <prism:section>Article</prism:section> <prism:startingPage>386</prism:startingPage> <prism:doi>10.3390/universe10100386</prism:doi> <prism:url>https://www.mdpi.com/2218-1997/10/10/386</prism:url> <cc:license rdf:resource="CC BY 4.0"/> </item> <item rdf:about="https://www.mdpi.com/2218-1997/10/10/385"> <title>Universe, Vol. 10, Pages 385: The Magellanic Clouds Are Very Rare in the IllustrisTNG Simulations</title> <link>https://www.mdpi.com/2218-1997/10/10/385</link> <description>The Large and Small Magellanic Clouds (LMC and SMC) form the closest interacting galactic system to the Milky Way, therewith providing a laboratory to test cosmological models in the local Universe. We quantify the likelihood for the Magellanic Clouds (MCs) to be observed within the &amp;Lambda;CDM model using hydrodynamical simulations of the IllustrisTNG project. The orbits of the MCs are constrained by proper motion measurements taken by the Hubble Space Telescope and Gaia. The MCs have a mutual separation of dMCs=24.5kpc and a relative velocity of vMCs=90.8kms&amp;minus;1, implying a specific phase-space density of fMCs,obs&amp;equiv;(dMCs&amp;middot;vMCs)&amp;minus;3=9.10&amp;times;10&amp;minus;11km&amp;minus;3s3kpc&amp;minus;3. We select analogues to the MCs based on their stellar masses and distances in MW-like halos. None of the selected LMC analogues have a higher total mass and lower Galactocentric distance than the LMC, resulting in &amp;gt;3.75&amp;sigma; tension. We also find that the fMCs distribution in the highest resolution TNG50 simulation is in 3.95&amp;sigma; tension with observations. Thus, a hierarchical clustering of two massive satellites like the MCs in a narrow phase-space volume is unlikely in &amp;Lambda;CDM, presumably because of short merger timescales due to dynamical friction between the overlapping dark matter halos. We show that group infall led by an LMC analogue cannot populate the Galactic disc of satellites (DoS), implying that the DoS and the MCs formed in physically unrelated ways in &amp;Lambda;CDM. Since the 20&amp;#8728; alignment of the LMC and DoS orbital poles has a likelihood of P=0.030 (2.17&amp;sigma;), adding this &amp;chi;2 to that of fMCs gives a combined likelihood of P=3.90&amp;times;10&amp;minus;5 (4.11&amp;sigma;).</description> <pubDate>2024-10-01</pubDate> <content:encoded><![CDATA[ Universe, Vol. 10, Pages 385: The Magellanic Clouds Are Very Rare in the IllustrisTNG Simulations Universe <a href="https://www.mdpi.com/2218-1997/10/10/385">doi: 10.3390/universe10100385</a> Authors: Moritz Haslbauer Indranil Banik Pavel Kroupa Hongsheng Zhao Elena Asencio The Large and Small Magellanic Clouds (LMC and SMC) form the closest interacting galactic system to the Milky Way, therewith providing a laboratory to test cosmological models in the local Universe. We quantify the likelihood for the Magellanic Clouds (MCs) to be observed within the &amp;Lambda;CDM model using hydrodynamical simulations of the IllustrisTNG project. The orbits of the MCs are constrained by proper motion measurements taken by the Hubble Space Telescope and Gaia. The MCs have a mutual separation of dMCs=24.5kpc and a relative velocity of vMCs=90.8kms&amp;minus;1, implying a specific phase-space density of fMCs,obs&amp;equiv;(dMCs&amp;middot;vMCs)&amp;minus;3=9.10&amp;times;10&amp;minus;11km&amp;minus;3s3kpc&amp;minus;3. We select analogues to the MCs based on their stellar masses and distances in MW-like halos. None of the selected LMC analogues have a higher total mass and lower Galactocentric distance than the LMC, resulting in &amp;gt;3.75&amp;sigma; tension. We also find that the fMCs distribution in the highest resolution TNG50 simulation is in 3.95&amp;sigma; tension with observations. Thus, a hierarchical clustering of two massive satellites like the MCs in a narrow phase-space volume is unlikely in &amp;Lambda;CDM, presumably because of short merger timescales due to dynamical friction between the overlapping dark matter halos. We show that group infall led by an LMC analogue cannot populate the Galactic disc of satellites (DoS), implying that the DoS and the MCs formed in physically unrelated ways in &amp;Lambda;CDM. Since the 20&amp;#8728; alignment of the LMC and DoS orbital poles has a likelihood of P=0.030 (2.17&amp;sigma;), adding this &amp;chi;2 to that of fMCs gives a combined likelihood of P=3.90&amp;times;10&amp;minus;5 (4.11&amp;sigma;). ]]></content:encoded> <dc:title>The Magellanic Clouds Are Very Rare in the IllustrisTNG Simulations</dc:title> <dc:creator>Moritz Haslbauer</dc:creator> <dc:creator>Indranil Banik</dc:creator> <dc:creator>Pavel Kroupa</dc:creator> <dc:creator>Hongsheng Zhao</dc:creator> <dc:creator>Elena Asencio</dc:creator> <dc:identifier>doi: 10.3390/universe10100385</dc:identifier> <dc:source>Universe</dc:source> <dc:date>2024-10-01</dc:date> <prism:publicationName>Universe</prism:publicationName> <prism:publicationDate>2024-10-01</prism:publicationDate> <prism:volume>10</prism:volume> <prism:number>10</prism:number> <prism:section>Article</prism:section> <prism:startingPage>385</prism:startingPage> <prism:doi>10.3390/universe10100385</prism:doi> <prism:url>https://www.mdpi.com/2218-1997/10/10/385</prism:url> <cc:license rdf:resource="CC BY 4.0"/> </item> <item rdf:about="https://www.mdpi.com/2218-1997/10/10/384"> <title>Universe, Vol. 10, Pages 384: Finite Time Path Field Theory Perturbative Methods for Local Quantum Spin Chain Quenches</title> <link>https://www.mdpi.com/2218-1997/10/10/384</link> <description>We discuss local magnetic field quenches using perturbative methods of finite time path field theory (FTPFT) in the following spin chains: Ising and XY in a transverse magnetic field. Their common characteristics are: (i) they are integrable via mapping to a second quantized noninteracting fermion problem; and (ii) when the ground state is nondegenerate (true for finite chains except in special cases), it can be represented as a vacuum of Bogoliubov fermions. By switching on a local magnetic field perturbation at finite time, the problem becomes nonintegrable and must be approached via numeric or perturbative methods. Using the formalism of FTPFT based on Wigner transforms (WTs) of projected functions, we show how to: (i) calculate the basic &amp;ldquo;bubble&amp;rdquo; diagram in the Loschmidt echo (LE) of a quenched chain to any order in the perturbation; and (ii) resum the generalized Schwinger&amp;ndash;Dyson equation for the fermion two-point retarded functions in the &amp;ldquo;bubble&amp;rdquo; diagram, hence achieving the resummation of perturbative expansion of LE for a wide range of perturbation strengths under certain analyticity assumptions. Limitations of the assumptions and possible generalizations beyond it and also for other spin chains are further discussed.</description> <pubDate>2024-09-30</pubDate> <content:encoded><![CDATA[ Universe, Vol. 10, Pages 384: Finite Time Path Field Theory Perturbative Methods for Local Quantum Spin Chain Quenches Universe <a href="https://www.mdpi.com/2218-1997/10/10/384">doi: 10.3390/universe10100384</a> Authors: Domagoj Kui膰 Alemka Knapp Diana 艩aponja-Milutinovi膰 We discuss local magnetic field quenches using perturbative methods of finite time path field theory (FTPFT) in the following spin chains: Ising and XY in a transverse magnetic field. Their common characteristics are: (i) they are integrable via mapping to a second quantized noninteracting fermion problem; and (ii) when the ground state is nondegenerate (true for finite chains except in special cases), it can be represented as a vacuum of Bogoliubov fermions. By switching on a local magnetic field perturbation at finite time, the problem becomes nonintegrable and must be approached via numeric or perturbative methods. Using the formalism of FTPFT based on Wigner transforms (WTs) of projected functions, we show how to: (i) calculate the basic &amp;ldquo;bubble&amp;rdquo; diagram in the Loschmidt echo (LE) of a quenched chain to any order in the perturbation; and (ii) resum the generalized Schwinger&amp;ndash;Dyson equation for the fermion two-point retarded functions in the &amp;ldquo;bubble&amp;rdquo; diagram, hence achieving the resummation of perturbative expansion of LE for a wide range of perturbation strengths under certain analyticity assumptions. Limitations of the assumptions and possible generalizations beyond it and also for other spin chains are further discussed. ]]></content:encoded> <dc:title>Finite Time Path Field Theory Perturbative Methods for Local Quantum Spin Chain Quenches</dc:title> <dc:creator>Domagoj Kui膰</dc:creator> <dc:creator>Alemka Knapp</dc:creator> <dc:creator>Diana 艩aponja-Milutinovi膰</dc:creator> <dc:identifier>doi: 10.3390/universe10100384</dc:identifier> <dc:source>Universe</dc:source> <dc:date>2024-09-30</dc:date> <prism:publicationName>Universe</prism:publicationName> <prism:publicationDate>2024-09-30</prism:publicationDate> <prism:volume>10</prism:volume> <prism:number>10</prism:number> <prism:section>Article</prism:section> <prism:startingPage>384</prism:startingPage> <prism:doi>10.3390/universe10100384</prism:doi> <prism:url>https://www.mdpi.com/2218-1997/10/10/384</prism:url> <cc:license rdf:resource="CC BY 4.0"/> </item> <item rdf:about="https://www.mdpi.com/2218-1997/10/10/383"> <title>Universe, Vol. 10, Pages 383: Constraining the Initial Mass Function via Stellar Transients</title> <link>https://www.mdpi.com/2218-1997/10/10/383</link> <description>The stellar initial mass function (IMF) represents a fundamental quantity in astrophysics and cosmology describing the mass distribution of stars from low mass all the way up to massive and very massive stars. It is intimately linked to a wide variety of topics, including stellar and binary evolution, galaxy evolution, chemical enrichment, and cosmological reionization. Nonetheless, the IMF still remains highly uncertain. In this work, we aim to determine the IMF with a novel approach based on the observed rates of transients of stellar origin. We parametrize the IMF with a simple but flexible Larson shape, and insert it into a parametric model for the cosmic UV luminosity density, local stellar mass density, type Ia supernova (SN Ia), core-collapse supernova (CCSN), and long gamma-ray burst (LGRB) rates as a function of redshift. We constrain our free parameters by matching the model predictions to a set of empirical determinations for the corresponding quantities via a Bayesian Markov Chain Monte Carlo method. Remarkably, we are able to provide an independent IMF determination with a characteristic mass mc=0.10&amp;minus;0.08+0.24M&amp;#8857; and high-mass slope &amp;xi;=&amp;minus;2.53&amp;minus;0.27+0.24 that are in accordance with the widely used IMF parameterizations (e.g., Salpeter, Kroupa, Chabrier). Moreover, the adoption of an up-to-date recipe for the cosmic metallicity evolution allows us to constrain the maximum metallicity of LGRB progenitors to Zmax=0.12&amp;minus;0.05+0.29Z&amp;#8857;. We also find which progenitor fraction actually leads to SN Ia or LGRB emission (e.g., due to binary interaction or jet-launching conditions), put constraints on the CCSN and LGRB progenitor mass ranges, and test the IMF universality. These results show the potential of this kind of approach for studying the IMF, its putative evolution with the galactic environment and cosmic history, and the properties of SN Ia, CCSN, and LGRB progenitors, especially considering the wealth of data incoming in the future.</description> <pubDate>2024-09-29</pubDate> <content:encoded><![CDATA[ Universe, Vol. 10, Pages 383: Constraining the Initial Mass Function via Stellar Transients Universe <a href="https://www.mdpi.com/2218-1997/10/10/383">doi: 10.3390/universe10100383</a> Authors: Francesco Gabrielli Lumen Boco Giancarlo Ghirlanda Om Sharan Salafia Ruben Salvaterra Mario Spera Andrea Lapi The stellar initial mass function (IMF) represents a fundamental quantity in astrophysics and cosmology describing the mass distribution of stars from low mass all the way up to massive and very massive stars. It is intimately linked to a wide variety of topics, including stellar and binary evolution, galaxy evolution, chemical enrichment, and cosmological reionization. Nonetheless, the IMF still remains highly uncertain. In this work, we aim to determine the IMF with a novel approach based on the observed rates of transients of stellar origin. We parametrize the IMF with a simple but flexible Larson shape, and insert it into a parametric model for the cosmic UV luminosity density, local stellar mass density, type Ia supernova (SN Ia), core-collapse supernova (CCSN), and long gamma-ray burst (LGRB) rates as a function of redshift. We constrain our free parameters by matching the model predictions to a set of empirical determinations for the corresponding quantities via a Bayesian Markov Chain Monte Carlo method. Remarkably, we are able to provide an independent IMF determination with a characteristic mass mc=0.10&amp;minus;0.08+0.24M&amp;#8857; and high-mass slope &amp;xi;=&amp;minus;2.53&amp;minus;0.27+0.24 that are in accordance with the widely used IMF parameterizations (e.g., Salpeter, Kroupa, Chabrier). Moreover, the adoption of an up-to-date recipe for the cosmic metallicity evolution allows us to constrain the maximum metallicity of LGRB progenitors to Zmax=0.12&amp;minus;0.05+0.29Z&amp;#8857;. We also find which progenitor fraction actually leads to SN Ia or LGRB emission (e.g., due to binary interaction or jet-launching conditions), put constraints on the CCSN and LGRB progenitor mass ranges, and test the IMF universality. These results show the potential of this kind of approach for studying the IMF, its putative evolution with the galactic environment and cosmic history, and the properties of SN Ia, CCSN, and LGRB progenitors, especially considering the wealth of data incoming in the future. ]]></content:encoded> <dc:title>Constraining the Initial Mass Function via Stellar Transients</dc:title> <dc:creator>Francesco Gabrielli</dc:creator> <dc:creator>Lumen Boco</dc:creator> <dc:creator>Giancarlo Ghirlanda</dc:creator> <dc:creator>Om Sharan Salafia</dc:creator> <dc:creator>Ruben Salvaterra</dc:creator> <dc:creator>Mario Spera</dc:creator> <dc:creator>Andrea Lapi</dc:creator> <dc:identifier>doi: 10.3390/universe10100383</dc:identifier> <dc:source>Universe</dc:source> <dc:date>2024-09-29</dc:date> <prism:publicationName>Universe</prism:publicationName> <prism:publicationDate>2024-09-29</prism:publicationDate> <prism:volume>10</prism:volume> <prism:number>10</prism:number> <prism:section>Article</prism:section> <prism:startingPage>383</prism:startingPage> <prism:doi>10.3390/universe10100383</prism:doi> <prism:url>https://www.mdpi.com/2218-1997/10/10/383</prism:url> <cc:license rdf:resource="CC BY 4.0"/> </item> <item rdf:about="https://www.mdpi.com/2218-1997/10/10/382"> <title>Universe, Vol. 10, Pages 382: The Effective Baryon&ndash;Baryon Potential with Configuration Mixing in Quark Models</title> <link>https://www.mdpi.com/2218-1997/10/10/382</link> <description>The effective baryon&amp;ndash;baryon potential can be derived in the framework of the quark model. The configurations with different quark spatial distributions are mixed naturally when two baryons get close. The effect of configuration mixing in the chiral quark model (ChQM) is studied by calculating the effective potential between two non-strange baryons in the channels IJ=01,10 and 03. For comparison, the results of the color screening model (CSM) are also presented. Generally, configuration mixing will lower the potential when the separation between two baryons is small, and its effect will be ignorable when the separation becomes large. Due to the screened color confinement, the effect of configuration mixing is rather large, which leads to stronger intermediate-range attraction in the CSM, while the effect of configuration mixing is small in the ChQM due to the quadratic confinement and &amp;sigma;-meson exchange, which is responsible for the intermediate-range attraction.</description> <pubDate>2024-09-29</pubDate> <content:encoded><![CDATA[ Universe, Vol. 10, Pages 382: The Effective Baryon&ndash;Baryon Potential with Configuration Mixing in Quark Models Universe <a href="https://www.mdpi.com/2218-1997/10/10/382">doi: 10.3390/universe10100382</a> Authors: Xinmei Zhu Hongxia Huang Jialun Ping The effective baryon&amp;ndash;baryon potential can be derived in the framework of the quark model. The configurations with different quark spatial distributions are mixed naturally when two baryons get close. The effect of configuration mixing in the chiral quark model (ChQM) is studied by calculating the effective potential between two non-strange baryons in the channels IJ=01,10 and 03. For comparison, the results of the color screening model (CSM) are also presented. Generally, configuration mixing will lower the potential when the separation between two baryons is small, and its effect will be ignorable when the separation becomes large. Due to the screened color confinement, the effect of configuration mixing is rather large, which leads to stronger intermediate-range attraction in the CSM, while the effect of configuration mixing is small in the ChQM due to the quadratic confinement and &amp;sigma;-meson exchange, which is responsible for the intermediate-range attraction. ]]></content:encoded> <dc:title>The Effective Baryon&amp;ndash;Baryon Potential with Configuration Mixing in Quark Models</dc:title> <dc:creator>Xinmei Zhu</dc:creator> <dc:creator>Hongxia Huang</dc:creator> <dc:creator>Jialun Ping</dc:creator> <dc:identifier>doi: 10.3390/universe10100382</dc:identifier> <dc:source>Universe</dc:source> <dc:date>2024-09-29</dc:date> <prism:publicationName>Universe</prism:publicationName> <prism:publicationDate>2024-09-29</prism:publicationDate> <prism:volume>10</prism:volume> <prism:number>10</prism:number> <prism:section>Article</prism:section> <prism:startingPage>382</prism:startingPage> <prism:doi>10.3390/universe10100382</prism:doi> <prism:url>https://www.mdpi.com/2218-1997/10/10/382</prism:url> <cc:license rdf:resource="CC BY 4.0"/> </item> <item rdf:about="https://www.mdpi.com/2218-1997/10/10/381"> <title>Universe, Vol. 10, Pages 381: Automated High-Precision Recognition of Solar Filaments Based on an Improved U2-Net</title> <link>https://www.mdpi.com/2218-1997/10/10/381</link> <description>Solar filaments are a significant solar activity phenomenon, typically observed in full-disk solar observations in the H-alpha band. They are closely associated with the magnetic fields of solar active regions, solar flare eruptions, and coronal mass ejections. With the increasing volume of observational data, the automated high-precision recognition of solar filaments using deep learning is crucial. In this study, we processed full-disk H-alpha solar images captured by the Chinese H-alpha Solar Explorer in 2023 to generate labels for solar filaments. The preprocessing steps included limb-darkening removal, grayscale transformation, K-means clustering, particle erosion, multiple closing operations, and hole filling. The dataset containing solar filament labels is constructed for deep learning. We developed the Attention U2-Net neural network for deep learning on the solar dataset by introducing an attention mechanism into U2-Net. In the results, Attention U2-Net achieved an average Accuracy of 0.9987, an average Precision of 0.8221, an average Recall of 0.8469, an average IoU of 0.7139, and an average F1-score of 0.8323 on the solar filament test set, showing significant improvements compared to other U-net variants.</description> <pubDate>2024-09-29</pubDate> <content:encoded><![CDATA[ Universe, Vol. 10, Pages 381: Automated High-Precision Recognition of Solar Filaments Based on an Improved U2-Net Universe <a href="https://www.mdpi.com/2218-1997/10/10/381">doi: 10.3390/universe10100381</a> Authors: Wendong Jiang Zhengyang Li Solar filaments are a significant solar activity phenomenon, typically observed in full-disk solar observations in the H-alpha band. They are closely associated with the magnetic fields of solar active regions, solar flare eruptions, and coronal mass ejections. With the increasing volume of observational data, the automated high-precision recognition of solar filaments using deep learning is crucial. In this study, we processed full-disk H-alpha solar images captured by the Chinese H-alpha Solar Explorer in 2023 to generate labels for solar filaments. The preprocessing steps included limb-darkening removal, grayscale transformation, K-means clustering, particle erosion, multiple closing operations, and hole filling. The dataset containing solar filament labels is constructed for deep learning. We developed the Attention U2-Net neural network for deep learning on the solar dataset by introducing an attention mechanism into U2-Net. In the results, Attention U2-Net achieved an average Accuracy of 0.9987, an average Precision of 0.8221, an average Recall of 0.8469, an average IoU of 0.7139, and an average F1-score of 0.8323 on the solar filament test set, showing significant improvements compared to other U-net variants. ]]></content:encoded> <dc:title>Automated High-Precision Recognition of Solar Filaments Based on an Improved U2-Net</dc:title> <dc:creator>Wendong Jiang</dc:creator> <dc:creator>Zhengyang Li</dc:creator> <dc:identifier>doi: 10.3390/universe10100381</dc:identifier> <dc:source>Universe</dc:source> <dc:date>2024-09-29</dc:date> <prism:publicationName>Universe</prism:publicationName> <prism:publicationDate>2024-09-29</prism:publicationDate> <prism:volume>10</prism:volume> <prism:number>10</prism:number> <prism:section>Article</prism:section> <prism:startingPage>381</prism:startingPage> <prism:doi>10.3390/universe10100381</prism:doi> <prism:url>https://www.mdpi.com/2218-1997/10/10/381</prism:url> <cc:license rdf:resource="CC BY 4.0"/> </item> <item rdf:about="https://www.mdpi.com/2218-1997/10/10/380"> <title>Universe, Vol. 10, Pages 380: Editorial to the Special Issue &ldquo;Universe: Feature Papers 2023&mdash;Cosmology&rdquo;</title> <link>https://www.mdpi.com/2218-1997/10/10/380</link> <description>According to recent observational data, including Supernovae Ia (SNe Ia) [...]</description> <pubDate>2024-09-27</pubDate> <content:encoded><![CDATA[ Universe, Vol. 10, Pages 380: Editorial to the Special Issue &ldquo;Universe: Feature Papers 2023&mdash;Cosmology&rdquo; Universe <a href="https://www.mdpi.com/2218-1997/10/10/380">doi: 10.3390/universe10100380</a> Authors: Kazuharu Bamba According to recent observational data, including Supernovae Ia (SNe Ia) [...] ]]></content:encoded> <dc:title>Editorial to the Special Issue &amp;ldquo;Universe: Feature Papers 2023&amp;mdash;Cosmology&amp;rdquo;</dc:title> <dc:creator>Kazuharu Bamba</dc:creator> <dc:identifier>doi: 10.3390/universe10100380</dc:identifier> <dc:source>Universe</dc:source> <dc:date>2024-09-27</dc:date> <prism:publicationName>Universe</prism:publicationName> <prism:publicationDate>2024-09-27</prism:publicationDate> <prism:volume>10</prism:volume> <prism:number>10</prism:number> <prism:section>Editorial</prism:section> <prism:startingPage>380</prism:startingPage> <prism:doi>10.3390/universe10100380</prism:doi> <prism:url>https://www.mdpi.com/2218-1997/10/10/380</prism:url> <cc:license rdf:resource="CC BY 4.0"/> </item> <item rdf:about="https://www.mdpi.com/2218-1997/10/9/379"> <title>Universe, Vol. 10, Pages 379: A Generic Analysis of Nucleon Decay Branching Fractions in Flipped SU(5) Grand Unification</title> <link>https://www.mdpi.com/2218-1997/10/9/379</link> <description>In flipped SU(5) grand unified theories, the partial decay lifetimes of certain nucleon decay channels depend generically on an unknown unitary matrix, which arises when left-handed lepton fields are embedded into anti-fundamental representations of SU(5). This dependency is particularly relevant when the neutrino mass matrix has a generic structure, introducing uncertainty in the prediction of nucleon decay branching fractions within flipped SU(5). In this paper, we demonstrate that this uncertainty can be parametrized using two parameters, which can be determined by measuring the partial lifetimes of p&amp;rarr;&amp;pi;0e+, p&amp;rarr;&amp;pi;0&amp;mu;+, and n&amp;rarr;&amp;pi;0&amp;nu;&amp;macr;. In addition, we establish upper limits on the ratios of the decay widths of these channels, offering a potential method to test flipped SU(5) in future nucleon decay experiments.</description> <pubDate>2024-09-23</pubDate> <content:encoded><![CDATA[ Universe, Vol. 10, Pages 379: A Generic Analysis of Nucleon Decay Branching Fractions in Flipped SU(5) Grand Unification Universe <a href="https://www.mdpi.com/2218-1997/10/9/379">doi: 10.3390/universe10090379</a> Authors: Koichi Hamaguchi Shihwen Hor Natsumi Nagata Hiroki Takahashi In flipped SU(5) grand unified theories, the partial decay lifetimes of certain nucleon decay channels depend generically on an unknown unitary matrix, which arises when left-handed lepton fields are embedded into anti-fundamental representations of SU(5). This dependency is particularly relevant when the neutrino mass matrix has a generic structure, introducing uncertainty in the prediction of nucleon decay branching fractions within flipped SU(5). In this paper, we demonstrate that this uncertainty can be parametrized using two parameters, which can be determined by measuring the partial lifetimes of p&amp;rarr;&amp;pi;0e+, p&amp;rarr;&amp;pi;0&amp;mu;+, and n&amp;rarr;&amp;pi;0&amp;nu;&amp;macr;. In addition, we establish upper limits on the ratios of the decay widths of these channels, offering a potential method to test flipped SU(5) in future nucleon decay experiments. ]]></content:encoded> <dc:title>A Generic Analysis of Nucleon Decay Branching Fractions in Flipped SU(5) Grand Unification</dc:title> <dc:creator>Koichi Hamaguchi</dc:creator> <dc:creator>Shihwen Hor</dc:creator> <dc:creator>Natsumi Nagata</dc:creator> <dc:creator>Hiroki Takahashi</dc:creator> <dc:identifier>doi: 10.3390/universe10090379</dc:identifier> <dc:source>Universe</dc:source> <dc:date>2024-09-23</dc:date> <prism:publicationName>Universe</prism:publicationName> <prism:publicationDate>2024-09-23</prism:publicationDate> <prism:volume>10</prism:volume> <prism:number>9</prism:number> <prism:section>Article</prism:section> <prism:startingPage>379</prism:startingPage> <prism:doi>10.3390/universe10090379</prism:doi> <prism:url>https://www.mdpi.com/2218-1997/10/9/379</prism:url> <cc:license rdf:resource="CC BY 4.0"/> </item> <item rdf:about="https://www.mdpi.com/2218-1997/10/9/378"> <title>Universe, Vol. 10, Pages 378: Sgr A* Shadow Study with KTN Space Time and Investigation of NUT Charge Existence</title> <link>https://www.mdpi.com/2218-1997/10/9/378</link> <description>In this paper, I investigate the existence of the NUT charge through the KTN spacetime using shadow observations of Sgr A*. I report that the range of my constraint for the NUT charge is between &amp;minus;0.5 and 0.5 for Schwarzschild-like and very slowly rotating KTN black holes. This range extends to 1.5 for spins up to &amp;minus;2 and &amp;minus;1.5 for spins up to 2 based on Keck observations for both 40&amp;deg; and 10&amp;deg; viewing angles. For VLTI observations, Schwarzschild-like and very slowly rotating KTN black holes are excluded for a 40&amp;deg; viewing angle, and the NUT charge is constrained to a very narrow range for a 10&amp;deg; viewing angle. I report that the possibility of having KTN naked singularities in Sgr A* is small, considering the uncertainties in the shadow size.</description> <pubDate>2024-09-23</pubDate> <content:encoded><![CDATA[ Universe, Vol. 10, Pages 378: Sgr A* Shadow Study with KTN Space Time and Investigation of NUT Charge Existence Universe <a href="https://www.mdpi.com/2218-1997/10/9/378">doi: 10.3390/universe10090378</a> Authors: Masoumeh Ghasemi-Nodehi In this paper, I investigate the existence of the NUT charge through the KTN spacetime using shadow observations of Sgr A*. I report that the range of my constraint for the NUT charge is between &amp;minus;0.5 and 0.5 for Schwarzschild-like and very slowly rotating KTN black holes. This range extends to 1.5 for spins up to &amp;minus;2 and &amp;minus;1.5 for spins up to 2 based on Keck observations for both 40&amp;deg; and 10&amp;deg; viewing angles. For VLTI observations, Schwarzschild-like and very slowly rotating KTN black holes are excluded for a 40&amp;deg; viewing angle, and the NUT charge is constrained to a very narrow range for a 10&amp;deg; viewing angle. I report that the possibility of having KTN naked singularities in Sgr A* is small, considering the uncertainties in the shadow size. ]]></content:encoded> <dc:title>Sgr A* Shadow Study with KTN Space Time and Investigation of NUT Charge Existence</dc:title> <dc:creator>Masoumeh Ghasemi-Nodehi</dc:creator> <dc:identifier>doi: 10.3390/universe10090378</dc:identifier> <dc:source>Universe</dc:source> <dc:date>2024-09-23</dc:date> <prism:publicationName>Universe</prism:publicationName> <prism:publicationDate>2024-09-23</prism:publicationDate> <prism:volume>10</prism:volume> <prism:number>9</prism:number> <prism:section>Communication</prism:section> <prism:startingPage>378</prism:startingPage> <prism:doi>10.3390/universe10090378</prism:doi> <prism:url>https://www.mdpi.com/2218-1997/10/9/378</prism:url> <cc:license rdf:resource="CC BY 4.0"/> </item> <item rdf:about="https://www.mdpi.com/2218-1997/10/9/377"> <title>Universe, Vol. 10, Pages 377: Topological Susceptibility of the Gluon Plasma in the Stochastic-Vacuum Approach</title> <link>https://www.mdpi.com/2218-1997/10/9/377</link> <description>Topological susceptibility of the SU(3) gluon plasma is calculated by accounting for both factorized and non-factorized contributions to the two-point correlation function of topological-charge densities. It turns out that, while the factorized contribution keeps this correlation function non-positive away from the origin, the non-factorized contribution makes it positive at the origin, in accordance with the reflection positivity condition. Matching the obtained result for topological susceptibility to its lattice value at the deconfinement critical temperature, we fix the parameters of the quartic cumulant of gluonic field strengths, and calculate the contribution of that cumulant to the string tension. This contribution reduces the otherwise too large value of the string tension, which stems from the quadratic cumulant, making it much closer to the standard phenomenological value.</description> <pubDate>2024-09-23</pubDate> <content:encoded><![CDATA[ Universe, Vol. 10, Pages 377: Topological Susceptibility of the Gluon Plasma in the Stochastic-Vacuum Approach Universe <a href="https://www.mdpi.com/2218-1997/10/9/377">doi: 10.3390/universe10090377</a> Authors: Dmitry Antonov Topological susceptibility of the SU(3) gluon plasma is calculated by accounting for both factorized and non-factorized contributions to the two-point correlation function of topological-charge densities. It turns out that, while the factorized contribution keeps this correlation function non-positive away from the origin, the non-factorized contribution makes it positive at the origin, in accordance with the reflection positivity condition. Matching the obtained result for topological susceptibility to its lattice value at the deconfinement critical temperature, we fix the parameters of the quartic cumulant of gluonic field strengths, and calculate the contribution of that cumulant to the string tension. This contribution reduces the otherwise too large value of the string tension, which stems from the quadratic cumulant, making it much closer to the standard phenomenological value. ]]></content:encoded> <dc:title>Topological Susceptibility of the Gluon Plasma in the Stochastic-Vacuum Approach</dc:title> <dc:creator>Dmitry Antonov</dc:creator> <dc:identifier>doi: 10.3390/universe10090377</dc:identifier> <dc:source>Universe</dc:source> <dc:date>2024-09-23</dc:date> <prism:publicationName>Universe</prism:publicationName> <prism:publicationDate>2024-09-23</prism:publicationDate> <prism:volume>10</prism:volume> <prism:number>9</prism:number> <prism:section>Article</prism:section> <prism:startingPage>377</prism:startingPage> <prism:doi>10.3390/universe10090377</prism:doi> <prism:url>https://www.mdpi.com/2218-1997/10/9/377</prism:url> <cc:license rdf:resource="CC BY 4.0"/> </item> <item rdf:about="https://www.mdpi.com/2218-1997/10/9/376"> <title>Universe, Vol. 10, Pages 376: Tensor Amplitudes for Partial Wave Analysis of &psi;&rarr;&Delta;&Delta;&macr; within Helicity Frame</title> <link>https://www.mdpi.com/2218-1997/10/9/376</link> <description>We have derived the tensor amplitudes for partial wave analysis of &amp;psi;&amp;rarr;&amp;Delta;&amp;Delta;&amp;macr;, &amp;Delta;&amp;rarr;p&amp;pi; within the helicity frame, as well as the amplitudes for the other decay sequences with same final states. These formulae are practical for the experiments measuring &amp;psi; decaying into pp&amp;macr;&amp;pi;+&amp;pi;&amp;minus; final states, such as BESIII with its recently collected huge J/&amp;psi; and &amp;psi;(2S) data samples.</description> <pubDate>2024-09-23</pubDate> <content:encoded><![CDATA[ Universe, Vol. 10, Pages 376: Tensor Amplitudes for Partial Wave Analysis of &psi;&rarr;&Delta;&Delta;&macr; within Helicity Frame Universe <a href="https://www.mdpi.com/2218-1997/10/9/376">doi: 10.3390/universe10090376</a> Authors: Xiang Dong Kexin Su Hao Cai Kai Zhu We have derived the tensor amplitudes for partial wave analysis of &amp;psi;&amp;rarr;&amp;Delta;&amp;Delta;&amp;macr;, &amp;Delta;&amp;rarr;p&amp;pi; within the helicity frame, as well as the amplitudes for the other decay sequences with same final states. These formulae are practical for the experiments measuring &amp;psi; decaying into pp&amp;macr;&amp;pi;+&amp;pi;&amp;minus; final states, such as BESIII with its recently collected huge J/&amp;psi; and &amp;psi;(2S) data samples. ]]></content:encoded> <dc:title>Tensor Amplitudes for Partial Wave Analysis of &amp;psi;&amp;rarr;&amp;Delta;&amp;Delta;&amp;macr; within Helicity Frame</dc:title> <dc:creator>Xiang Dong</dc:creator> <dc:creator>Kexin Su</dc:creator> <dc:creator>Hao Cai</dc:creator> <dc:creator>Kai Zhu</dc:creator> <dc:identifier>doi: 10.3390/universe10090376</dc:identifier> <dc:source>Universe</dc:source> <dc:date>2024-09-23</dc:date> <prism:publicationName>Universe</prism:publicationName> <prism:publicationDate>2024-09-23</prism:publicationDate> <prism:volume>10</prism:volume> <prism:number>9</prism:number> <prism:section>Article</prism:section> <prism:startingPage>376</prism:startingPage> <prism:doi>10.3390/universe10090376</prism:doi> <prism:url>https://www.mdpi.com/2218-1997/10/9/376</prism:url> <cc:license rdf:resource="CC BY 4.0"/> </item> <item rdf:about="https://www.mdpi.com/2218-1997/10/9/375"> <title>Universe, Vol. 10, Pages 375: On the Euler&ndash;Type Gravitomagnetic Orbital Effects in the Field of a Precessing Body</title> <link>https://www.mdpi.com/2218-1997/10/9/375</link> <description>To the first post&amp;ndash;Newtonian order, the gravitational action of mass&amp;ndash;energy currents is encoded by the off&amp;ndash;diagonal gravitomagnetic components of the spacetime metric tensor. If they are time&amp;ndash;dependent, a further acceleration enters the equations of motion of a moving test particle. Let the source of the gravitational field be an isolated, massive body rigidly rotating whose spin angular momentum experiences a slow precessional motion. The impact of the aforementioned acceleration on the orbital motion of a test particle is analytically worked out in full generality. The resulting averaged rates of change are valid for any orbital configuration of the satellite; furthermore, they hold for an arbitrary orientation of the precessional velocity vector of the spin of the central object. In general, all the orbital elements, with the exception of the mean anomaly at epoch, undergo nonvanishing long&amp;ndash;term variations which, in the case of the Juno spacecraft currently orbiting Jupiter and the double pulsar PSR J0737&amp;ndash;3039 A/B turn out to be quite small. Such effects might become much more relevant in a star&amp;ndash;supermassive black hole scenario; as an example, the relative change of the semimajor axis of a putative test particle orbiting a Kerr black hole as massive as the one at the Galactic Centre at, say, 100 Schwarzschild radii may amount up to about 7% per year if the hole&amp;rsquo;s spin precessional frequency is 10% of the particle&amp;rsquo;s orbital one.</description> <pubDate>2024-09-21</pubDate> <content:encoded><![CDATA[ Universe, Vol. 10, Pages 375: On the Euler&ndash;Type Gravitomagnetic Orbital Effects in the Field of a Precessing Body Universe <a href="https://www.mdpi.com/2218-1997/10/9/375">doi: 10.3390/universe10090375</a> Authors: Lorenzo Iorio To the first post&amp;ndash;Newtonian order, the gravitational action of mass&amp;ndash;energy currents is encoded by the off&amp;ndash;diagonal gravitomagnetic components of the spacetime metric tensor. If they are time&amp;ndash;dependent, a further acceleration enters the equations of motion of a moving test particle. Let the source of the gravitational field be an isolated, massive body rigidly rotating whose spin angular momentum experiences a slow precessional motion. The impact of the aforementioned acceleration on the orbital motion of a test particle is analytically worked out in full generality. The resulting averaged rates of change are valid for any orbital configuration of the satellite; furthermore, they hold for an arbitrary orientation of the precessional velocity vector of the spin of the central object. In general, all the orbital elements, with the exception of the mean anomaly at epoch, undergo nonvanishing long&amp;ndash;term variations which, in the case of the Juno spacecraft currently orbiting Jupiter and the double pulsar PSR J0737&amp;ndash;3039 A/B turn out to be quite small. Such effects might become much more relevant in a star&amp;ndash;supermassive black hole scenario; as an example, the relative change of the semimajor axis of a putative test particle orbiting a Kerr black hole as massive as the one at the Galactic Centre at, say, 100 Schwarzschild radii may amount up to about 7% per year if the hole&amp;rsquo;s spin precessional frequency is 10% of the particle&amp;rsquo;s orbital one. ]]></content:encoded> <dc:title>On the Euler&amp;ndash;Type Gravitomagnetic Orbital Effects in the Field of a Precessing Body</dc:title> <dc:creator>Lorenzo Iorio</dc:creator> <dc:identifier>doi: 10.3390/universe10090375</dc:identifier> <dc:source>Universe</dc:source> <dc:date>2024-09-21</dc:date> <prism:publicationName>Universe</prism:publicationName> <prism:publicationDate>2024-09-21</prism:publicationDate> <prism:volume>10</prism:volume> <prism:number>9</prism:number> <prism:section>Article</prism:section> <prism:startingPage>375</prism:startingPage> <prism:doi>10.3390/universe10090375</prism:doi> <prism:url>https://www.mdpi.com/2218-1997/10/9/375</prism:url> <cc:license rdf:resource="CC BY 4.0"/> </item> <item rdf:about="https://www.mdpi.com/2218-1997/10/9/374"> <title>Universe, Vol. 10, Pages 374: Dynamics of Two Planets near a 2:1 Resonance: Case Studies of Known and Synthetic Exosystems on a Grid of Initial Configurations</title> <link>https://www.mdpi.com/2218-1997/10/9/374</link> <description>The distribution of period ratios for 580 known two-planet systems is apparently nonuniform, with several sharp peaks and troughs. In particular, the vicinity of the 2:1 commensurability seems to have a deficit of systems. Using Monte Carlo simulations and an empirically inferred population distribution of period ratios, we prove that this apparent dearth of near-resonant systems is not statistically significant. The excess of systems with period ratios in the wider vicinity of the 2:1 resonance is significant, however. Long-term WHFast integrations of a synthetic two-planet system on a grid period ratios from 1.87 through 2.12 reveal that the eccentricity and inclination exchange mechanism between non-resonant planets represents the orbital evolution very well in all cases, except at the exact 2:1 mean motion resonance. This resonance destroys the orderly exchange of eccentricity, while the exchange of inclination still takes place. Additional simulations of the Kepler-113 system on a grid of initial inclinations show that the secular periods of eccentricity and inclination variations are well fitted by a simple hyperbolic cosine function of the initial mutual inclination. We further investigate the six known two-planet systems with period ratios within 2% of the exact 2:1 resonance (TOI-216, KIC 5437945, Kepler-384, HD 82943, HD 73526, HD 155358) on a grid of initial inclinations and for two different initial periastron longitudes corresponding to the aligned and anti-aligned states. All these systems are found to be long-term stable except HD 73526, which is likely a false positive. The periodic orbital momentum exchange is still at work in some of these systems, albeit with much shorter cycling periods of a few years.</description> <pubDate>2024-09-19</pubDate> <content:encoded><![CDATA[ Universe, Vol. 10, Pages 374: Dynamics of Two Planets near a 2:1 Resonance: Case Studies of Known and Synthetic Exosystems on a Grid of Initial Configurations Universe <a href="https://www.mdpi.com/2218-1997/10/9/374">doi: 10.3390/universe10090374</a> Authors: Valeri Makarov Alexey Goldin Dimitri Veras The distribution of period ratios for 580 known two-planet systems is apparently nonuniform, with several sharp peaks and troughs. In particular, the vicinity of the 2:1 commensurability seems to have a deficit of systems. Using Monte Carlo simulations and an empirically inferred population distribution of period ratios, we prove that this apparent dearth of near-resonant systems is not statistically significant. The excess of systems with period ratios in the wider vicinity of the 2:1 resonance is significant, however. Long-term WHFast integrations of a synthetic two-planet system on a grid period ratios from 1.87 through 2.12 reveal that the eccentricity and inclination exchange mechanism between non-resonant planets represents the orbital evolution very well in all cases, except at the exact 2:1 mean motion resonance. This resonance destroys the orderly exchange of eccentricity, while the exchange of inclination still takes place. Additional simulations of the Kepler-113 system on a grid of initial inclinations show that the secular periods of eccentricity and inclination variations are well fitted by a simple hyperbolic cosine function of the initial mutual inclination. We further investigate the six known two-planet systems with period ratios within 2% of the exact 2:1 resonance (TOI-216, KIC 5437945, Kepler-384, HD 82943, HD 73526, HD 155358) on a grid of initial inclinations and for two different initial periastron longitudes corresponding to the aligned and anti-aligned states. All these systems are found to be long-term stable except HD 73526, which is likely a false positive. The periodic orbital momentum exchange is still at work in some of these systems, albeit with much shorter cycling periods of a few years. ]]></content:encoded> <dc:title>Dynamics of Two Planets near a 2:1 Resonance: Case Studies of Known and Synthetic Exosystems on a Grid of Initial Configurations</dc:title> <dc:creator>Valeri Makarov</dc:creator> <dc:creator>Alexey Goldin</dc:creator> <dc:creator>Dimitri Veras</dc:creator> <dc:identifier>doi: 10.3390/universe10090374</dc:identifier> <dc:source>Universe</dc:source> <dc:date>2024-09-19</dc:date> <prism:publicationName>Universe</prism:publicationName> <prism:publicationDate>2024-09-19</prism:publicationDate> <prism:volume>10</prism:volume> <prism:number>9</prism:number> <prism:section>Article</prism:section> <prism:startingPage>374</prism:startingPage> <prism:doi>10.3390/universe10090374</prism:doi> <prism:url>https://www.mdpi.com/2218-1997/10/9/374</prism:url> <cc:license rdf:resource="CC BY 4.0"/> </item> <item rdf:about="https://www.mdpi.com/2218-1997/10/9/373"> <title>Universe, Vol. 10, Pages 373: Time-Series Feature Selection for Solar Flare Forecasting</title> <link>https://www.mdpi.com/2218-1997/10/9/373</link> <description>Solar flares are significant occurrences in solar physics, impacting space weather and terrestrial technologies. Accurate classification of solar flares is essential for predicting space weather and minimizing potential disruptions to communication, navigation, and power systems. This study addresses the challenge of selecting the most relevant features from multivariate time-series data, specifically focusing on solar flares. We employ methods such as Mutual Information (MI), Minimum Redundancy Maximum Relevance (mRMR), and Euclidean Distance to identify key features for classification. Recognizing the performance variability of different feature selection techniques, we introduce an ensemble approach to compute feature weights. By combining outputs from multiple methods, our ensemble method provides a more comprehensive understanding of the importance of features. Our results show that the ensemble approach significantly improves classification performance, achieving values 0.15 higher in True Skill Statistic (TSS) values compared to individual feature selection methods. Additionally, our method offers valuable insights into the underlying physical processes of solar flares, leading to more effective space weather forecasting and enhanced mitigation strategies for communication, navigation, and power system disruptions.</description> <pubDate>2024-09-19</pubDate> <content:encoded><![CDATA[ Universe, Vol. 10, Pages 373: Time-Series Feature Selection for Solar Flare Forecasting Universe <a href="https://www.mdpi.com/2218-1997/10/9/373">doi: 10.3390/universe10090373</a> Authors: Yagnashree Velanki Pouya Hosseinzadeh Soukaina Filali Boubrahimi Shah Muhammad Hamdi Solar flares are significant occurrences in solar physics, impacting space weather and terrestrial technologies. Accurate classification of solar flares is essential for predicting space weather and minimizing potential disruptions to communication, navigation, and power systems. This study addresses the challenge of selecting the most relevant features from multivariate time-series data, specifically focusing on solar flares. We employ methods such as Mutual Information (MI), Minimum Redundancy Maximum Relevance (mRMR), and Euclidean Distance to identify key features for classification. Recognizing the performance variability of different feature selection techniques, we introduce an ensemble approach to compute feature weights. By combining outputs from multiple methods, our ensemble method provides a more comprehensive understanding of the importance of features. Our results show that the ensemble approach significantly improves classification performance, achieving values 0.15 higher in True Skill Statistic (TSS) values compared to individual feature selection methods. Additionally, our method offers valuable insights into the underlying physical processes of solar flares, leading to more effective space weather forecasting and enhanced mitigation strategies for communication, navigation, and power system disruptions. ]]></content:encoded> <dc:title>Time-Series Feature Selection for Solar Flare Forecasting</dc:title> <dc:creator>Yagnashree Velanki</dc:creator> <dc:creator>Pouya Hosseinzadeh</dc:creator> <dc:creator>Soukaina Filali Boubrahimi</dc:creator> <dc:creator>Shah Muhammad Hamdi</dc:creator> <dc:identifier>doi: 10.3390/universe10090373</dc:identifier> <dc:source>Universe</dc:source> <dc:date>2024-09-19</dc:date> <prism:publicationName>Universe</prism:publicationName> <prism:publicationDate>2024-09-19</prism:publicationDate> <prism:volume>10</prism:volume> <prism:number>9</prism:number> <prism:section>Article</prism:section> <prism:startingPage>373</prism:startingPage> <prism:doi>10.3390/universe10090373</prism:doi> <prism:url>https://www.mdpi.com/2218-1997/10/9/373</prism:url> <cc:license rdf:resource="CC BY 4.0"/> </item> <item rdf:about="https://www.mdpi.com/2218-1997/10/9/372"> <title>Universe, Vol. 10, Pages 372: Quantum Field Theory of Black Hole Perturbations with Backreaction: I General Framework</title> <link>https://www.mdpi.com/2218-1997/10/9/372</link> <description>In a seminal work, Hawking showed that natural states for free quantum matter fields on classical spacetimes that solve the spherically symmetric vacuum Einstein equations are KMS states of non-vanishing temperature. Although Hawking&amp;rsquo;s calculation does not include the backreaction of matter on geometry, it is more than plausible that the corresponding Hawking radiation leads to black hole evaporation which is, in principle, observable. Obviously, an improvement of Hawking&amp;rsquo;s calculation including backreaction is a problem of quantum gravity. Since no commonly accepted quantum field theory of general relativity is available yet, it has been difficult to reliably derive the backreaction effect. An obvious approach is to use the black hole perturbation theory of a Schwarzschild black hole of fixed mass and to quantize those perturbations. However, it is not clear how to reconcile perturbation theory with gauge invariance beyond linear perturbations. In recent work, we proposed a new approach to this problem that applies when the physical situation has an approximate symmetry, such as homogeneity (cosmology), spherical symmetry (Schwarzschild), or axial symmetry (Kerr). The idea, which is surprisingly feasible, is to first construct the non-perturbative physical (reduced) Hamiltonian of the reduced phase space of fully gauge invariant observables and only then apply perturbation theory directly in terms of observables. The task to construct observables is then disentangled from perturbation theory, thus allowing to unambiguously develop perturbation theory to arbitrary orders. In this first paper of the series we outline and showcase this approach for spherical symmetry and second order in the perturbations for Einstein&amp;ndash;Klein&amp;ndash;Gordon&amp;ndash;Maxwell theory. Details and generalizations to other matter and symmetry and higher orders will appear in subsequent companion papers.</description> <pubDate>2024-09-18</pubDate> <content:encoded><![CDATA[ Universe, Vol. 10, Pages 372: Quantum Field Theory of Black Hole Perturbations with Backreaction: I General Framework Universe <a href="https://www.mdpi.com/2218-1997/10/9/372">doi: 10.3390/universe10090372</a> Authors: Thomas Thiemann In a seminal work, Hawking showed that natural states for free quantum matter fields on classical spacetimes that solve the spherically symmetric vacuum Einstein equations are KMS states of non-vanishing temperature. Although Hawking&amp;rsquo;s calculation does not include the backreaction of matter on geometry, it is more than plausible that the corresponding Hawking radiation leads to black hole evaporation which is, in principle, observable. Obviously, an improvement of Hawking&amp;rsquo;s calculation including backreaction is a problem of quantum gravity. Since no commonly accepted quantum field theory of general relativity is available yet, it has been difficult to reliably derive the backreaction effect. An obvious approach is to use the black hole perturbation theory of a Schwarzschild black hole of fixed mass and to quantize those perturbations. However, it is not clear how to reconcile perturbation theory with gauge invariance beyond linear perturbations. In recent work, we proposed a new approach to this problem that applies when the physical situation has an approximate symmetry, such as homogeneity (cosmology), spherical symmetry (Schwarzschild), or axial symmetry (Kerr). The idea, which is surprisingly feasible, is to first construct the non-perturbative physical (reduced) Hamiltonian of the reduced phase space of fully gauge invariant observables and only then apply perturbation theory directly in terms of observables. The task to construct observables is then disentangled from perturbation theory, thus allowing to unambiguously develop perturbation theory to arbitrary orders. In this first paper of the series we outline and showcase this approach for spherical symmetry and second order in the perturbations for Einstein&amp;ndash;Klein&amp;ndash;Gordon&amp;ndash;Maxwell theory. Details and generalizations to other matter and symmetry and higher orders will appear in subsequent companion papers. ]]></content:encoded> <dc:title>Quantum Field Theory of Black Hole Perturbations with Backreaction: I General Framework</dc:title> <dc:creator>Thomas Thiemann</dc:creator> <dc:identifier>doi: 10.3390/universe10090372</dc:identifier> <dc:source>Universe</dc:source> <dc:date>2024-09-18</dc:date> <prism:publicationName>Universe</prism:publicationName> <prism:publicationDate>2024-09-18</prism:publicationDate> <prism:volume>10</prism:volume> <prism:number>9</prism:number> <prism:section>Article</prism:section> <prism:startingPage>372</prism:startingPage> <prism:doi>10.3390/universe10090372</prism:doi> <prism:url>https://www.mdpi.com/2218-1997/10/9/372</prism:url> <cc:license rdf:resource="CC BY 4.0"/> </item> <item rdf:about="https://www.mdpi.com/2218-1997/10/9/371"> <title>Universe, Vol. 10, Pages 371: Constraints on Metastable Dark Energy Decaying into Dark Matter</title> <link>https://www.mdpi.com/2218-1997/10/9/371</link> <description>We revisit the proposal that an energy transfer from dark energy into dark matter can be described in field theory by a first order phase transition. We analyze a metastable dark energy model proposed in the literature, using updated constraints on the decay time of a metastable dark energy from recent data. The results of our analysis show no prospects for potentially observable signals that could distinguish this scenario from the &amp;Lambda;CDM. We analyze, for the first time, the process of bubble nucleation in this model, showing that such model would not drive a complete transition to a dark matter dominated phase even in a distant future. Nevertheless, the model is not excluded by the latest data and we confirm that the mass of the dark matter particle that would result from such a process corresponds to the mass of an axion-like particle, which is currently one of the best motivated dark matter candidates. We argue that extensions to this model, possibly with additional couplings, still deserve further attention as it could provide an interesting and viable description for an interacting dark sector scenario based in a single scalar field.</description> <pubDate>2024-09-18</pubDate> <content:encoded><![CDATA[ Universe, Vol. 10, Pages 371: Constraints on Metastable Dark Energy Decaying into Dark Matter Universe <a href="https://www.mdpi.com/2218-1997/10/9/371">doi: 10.3390/universe10090371</a> Authors: J么nathas S. T. de Souza Gustavo S. Vicente Leila L. Graef We revisit the proposal that an energy transfer from dark energy into dark matter can be described in field theory by a first order phase transition. We analyze a metastable dark energy model proposed in the literature, using updated constraints on the decay time of a metastable dark energy from recent data. The results of our analysis show no prospects for potentially observable signals that could distinguish this scenario from the &amp;Lambda;CDM. We analyze, for the first time, the process of bubble nucleation in this model, showing that such model would not drive a complete transition to a dark matter dominated phase even in a distant future. Nevertheless, the model is not excluded by the latest data and we confirm that the mass of the dark matter particle that would result from such a process corresponds to the mass of an axion-like particle, which is currently one of the best motivated dark matter candidates. We argue that extensions to this model, possibly with additional couplings, still deserve further attention as it could provide an interesting and viable description for an interacting dark sector scenario based in a single scalar field. ]]></content:encoded> <dc:title>Constraints on Metastable Dark Energy Decaying into Dark Matter</dc:title> <dc:creator>J么nathas S. T. de Souza</dc:creator> <dc:creator>Gustavo S. Vicente</dc:creator> <dc:creator>Leila L. Graef</dc:creator> <dc:identifier>doi: 10.3390/universe10090371</dc:identifier> <dc:source>Universe</dc:source> <dc:date>2024-09-18</dc:date> <prism:publicationName>Universe</prism:publicationName> <prism:publicationDate>2024-09-18</prism:publicationDate> <prism:volume>10</prism:volume> <prism:number>9</prism:number> <prism:section>Article</prism:section> <prism:startingPage>371</prism:startingPage> <prism:doi>10.3390/universe10090371</prism:doi> <prism:url>https://www.mdpi.com/2218-1997/10/9/371</prism:url> <cc:license rdf:resource="CC BY 4.0"/> </item> <item rdf:about="https://www.mdpi.com/2218-1997/10/9/370"> <title>Universe, Vol. 10, Pages 370: Bayesian Knowledge Infusion for Studying Historical Sunspot Numbers</title> <link>https://www.mdpi.com/2218-1997/10/9/370</link> <description>A scientific method that proposes a value Y to estimate a target value &amp;rho; is often subject to some level of uncertainty. In the Bayesian framework, the level of uncertainty can be measured by the width of the 68% interval, which is the range of the middle 68% of the ranked &amp;rho; values sampled from the posterior distribution p(&amp;rho;|Y). This paper considers Bayesian knowledge infusion (BKI) to reduce the uncertainty of the posterior distribution p(&amp;rho;|Y) based on additional knowledge that an event A happens. BKI is achieved by using a conditional prior distribution p(&amp;rho;|A) in the Bayes theorem, assuming that given the true &amp;rho;, its error-contaminated value Y is independent of event A. We use two examples to illustrate how to study whether or not it is possible to reduce uncertainty from 14C reconstruction (Y) of the annual sunspot number (SSN) (&amp;rho;) by infusing additional information (A) using BKI. Information (A) that SSN is from a year that has a Far Eastern record of naked eye sunspots is found to be not so effective in reducing the uncertainty. In contrast, information that SSN is from a year at a cycle minimum is found to be very effective, producing much narrower 68% intervals. The resulting Bayesian point estimates of SSN (the posterior medians of &amp;rho;) are cross-validated and tested on a subset of telescopically observed SSNs that were unused in the process of Bayes computation.</description> <pubDate>2024-09-14</pubDate> <content:encoded><![CDATA[ Universe, Vol. 10, Pages 370: Bayesian Knowledge Infusion for Studying Historical Sunspot Numbers Universe <a href="https://www.mdpi.com/2218-1997/10/9/370">doi: 10.3390/universe10090370</a> Authors: Wenxin Jiang Haisheng Ji A scientific method that proposes a value Y to estimate a target value &amp;rho; is often subject to some level of uncertainty. In the Bayesian framework, the level of uncertainty can be measured by the width of the 68% interval, which is the range of the middle 68% of the ranked &amp;rho; values sampled from the posterior distribution p(&amp;rho;|Y). This paper considers Bayesian knowledge infusion (BKI) to reduce the uncertainty of the posterior distribution p(&amp;rho;|Y) based on additional knowledge that an event A happens. BKI is achieved by using a conditional prior distribution p(&amp;rho;|A) in the Bayes theorem, assuming that given the true &amp;rho;, its error-contaminated value Y is independent of event A. We use two examples to illustrate how to study whether or not it is possible to reduce uncertainty from 14C reconstruction (Y) of the annual sunspot number (SSN) (&amp;rho;) by infusing additional information (A) using BKI. Information (A) that SSN is from a year that has a Far Eastern record of naked eye sunspots is found to be not so effective in reducing the uncertainty. In contrast, information that SSN is from a year at a cycle minimum is found to be very effective, producing much narrower 68% intervals. The resulting Bayesian point estimates of SSN (the posterior medians of &amp;rho;) are cross-validated and tested on a subset of telescopically observed SSNs that were unused in the process of Bayes computation. ]]></content:encoded> <dc:title>Bayesian Knowledge Infusion for Studying Historical Sunspot Numbers</dc:title> <dc:creator>Wenxin Jiang</dc:creator> <dc:creator>Haisheng Ji</dc:creator> <dc:identifier>doi: 10.3390/universe10090370</dc:identifier> <dc:source>Universe</dc:source> <dc:date>2024-09-14</dc:date> <prism:publicationName>Universe</prism:publicationName> <prism:publicationDate>2024-09-14</prism:publicationDate> <prism:volume>10</prism:volume> <prism:number>9</prism:number> <prism:section>Article</prism:section> <prism:startingPage>370</prism:startingPage> <prism:doi>10.3390/universe10090370</prism:doi> <prism:url>https://www.mdpi.com/2218-1997/10/9/370</prism:url> <cc:license rdf:resource="CC BY 4.0"/> </item> <item rdf:about="https://www.mdpi.com/2218-1997/10/9/369"> <title>Universe, Vol. 10, Pages 369: Primordial Axion Stars and Galaxy Halo Formation</title> <link>https://www.mdpi.com/2218-1997/10/9/369</link> <description>Primordial axion stars, hypothetical stars formed from axions, could play an essential role in forming galaxy halos. These stars could have originated in the early universe shortly after the Big Bang. We show that the ultralight axions forming primordial stars can act as the initial seeds for galaxy halos.</description> <pubDate>2024-09-12</pubDate> <content:encoded><![CDATA[ Universe, Vol. 10, Pages 369: Primordial Axion Stars and Galaxy Halo Formation Universe <a href="https://www.mdpi.com/2218-1997/10/9/369">doi: 10.3390/universe10090369</a> Authors: Alexander I. Nesterov Primordial axion stars, hypothetical stars formed from axions, could play an essential role in forming galaxy halos. These stars could have originated in the early universe shortly after the Big Bang. We show that the ultralight axions forming primordial stars can act as the initial seeds for galaxy halos. ]]></content:encoded> <dc:title>Primordial Axion Stars and Galaxy Halo Formation</dc:title> <dc:creator>Alexander I. Nesterov</dc:creator> <dc:identifier>doi: 10.3390/universe10090369</dc:identifier> <dc:source>Universe</dc:source> <dc:date>2024-09-12</dc:date> <prism:publicationName>Universe</prism:publicationName> <prism:publicationDate>2024-09-12</prism:publicationDate> <prism:volume>10</prism:volume> <prism:number>9</prism:number> <prism:section>Article</prism:section> <prism:startingPage>369</prism:startingPage> <prism:doi>10.3390/universe10090369</prism:doi> <prism:url>https://www.mdpi.com/2218-1997/10/9/369</prism:url> <cc:license rdf:resource="CC BY 4.0"/> </item> <item rdf:about="https://www.mdpi.com/2218-1997/10/9/368"> <title>Universe, Vol. 10, Pages 368: Dark Atoms of Nuclear Interacting Dark Matter</title> <link>https://www.mdpi.com/2218-1997/10/9/368</link> <description>The lack of positive evidence for Weakly Interacting Massive Particles (WIMPs) as well as the lack of discovery of supersymmetric (SUSY) particles at the LHC may appeal to a non-supersymmetric solution for the Standard Model problem of the Higgs boson mass divergence, the origin of the electroweak energy scale and the physical nature of the cosmological dark matter in the approach of composite Higgs boson. If the Higgs boson consists of charged constituents, their binding can lead to stable particles with electroweak charges. Such particles can take part in sphaleron transitions in the early Universe, which balance their excess with baryon asymmetry. Constraints on exotic charged species leave only stable particles with charge &amp;minus;2n possible, which can bind with n nuclei of primordial helium in neutral dark atoms. The predicted ratio of densities of dark atoms and baryonic matter determines the condition for dark atoms to dominate in the cosmological dark matter. To satisfy this condition of the dark-atom nature of the observed dark matter, the mass of new stable &amp;minus;2n charged particles should be within reach of the LHC for their searches. We discuss the possibilities of dark-atom binding in multi-atom systems and present state-of-the-art quantum mechanical descriptions of dark-atom interactions with nuclei. Annual modulations in such interactions with nuclei of underground detectors can explain the positive results of DAMA/NaI and DAMA/LIBRA experiments and the negative results of the underground WIMP searches.</description> <pubDate>2024-09-11</pubDate> <content:encoded><![CDATA[ Universe, Vol. 10, Pages 368: Dark Atoms of Nuclear Interacting Dark Matter Universe <a href="https://www.mdpi.com/2218-1997/10/9/368">doi: 10.3390/universe10090368</a> Authors: Vitaly A. Beylin Timur E. Bikbaev Maxim Yu. Khlopov Andrey G. Mayorov Danila O. Sopin The lack of positive evidence for Weakly Interacting Massive Particles (WIMPs) as well as the lack of discovery of supersymmetric (SUSY) particles at the LHC may appeal to a non-supersymmetric solution for the Standard Model problem of the Higgs boson mass divergence, the origin of the electroweak energy scale and the physical nature of the cosmological dark matter in the approach of composite Higgs boson. If the Higgs boson consists of charged constituents, their binding can lead to stable particles with electroweak charges. Such particles can take part in sphaleron transitions in the early Universe, which balance their excess with baryon asymmetry. Constraints on exotic charged species leave only stable particles with charge &amp;minus;2n possible, which can bind with n nuclei of primordial helium in neutral dark atoms. The predicted ratio of densities of dark atoms and baryonic matter determines the condition for dark atoms to dominate in the cosmological dark matter. To satisfy this condition of the dark-atom nature of the observed dark matter, the mass of new stable &amp;minus;2n charged particles should be within reach of the LHC for their searches. We discuss the possibilities of dark-atom binding in multi-atom systems and present state-of-the-art quantum mechanical descriptions of dark-atom interactions with nuclei. Annual modulations in such interactions with nuclei of underground detectors can explain the positive results of DAMA/NaI and DAMA/LIBRA experiments and the negative results of the underground WIMP searches. ]]></content:encoded> <dc:title>Dark Atoms of Nuclear Interacting Dark Matter</dc:title> <dc:creator>Vitaly A. Beylin</dc:creator> <dc:creator>Timur E. Bikbaev</dc:creator> <dc:creator>Maxim Yu. Khlopov</dc:creator> <dc:creator>Andrey G. Mayorov</dc:creator> <dc:creator>Danila O. Sopin</dc:creator> <dc:identifier>doi: 10.3390/universe10090368</dc:identifier> <dc:source>Universe</dc:source> <dc:date>2024-09-11</dc:date> <prism:publicationName>Universe</prism:publicationName> <prism:publicationDate>2024-09-11</prism:publicationDate> <prism:volume>10</prism:volume> <prism:number>9</prism:number> <prism:section>Article</prism:section> <prism:startingPage>368</prism:startingPage> <prism:doi>10.3390/universe10090368</prism:doi> <prism:url>https://www.mdpi.com/2218-1997/10/9/368</prism:url> <cc:license rdf:resource="CC BY 4.0"/> </item> <item rdf:about="https://www.mdpi.com/2218-1997/10/9/367"> <title>Universe, Vol. 10, Pages 367: The Operational Meaning of Total Energy of Isolated Systems in General Relativity</title> <link>https://www.mdpi.com/2218-1997/10/9/367</link> <description>We present thought experiments to measure the Arnowitt&amp;ndash;Deser&amp;ndash;Misner EADM and Bondi&amp;ndash;Sachs energy EBS of isolated systems in general relativity. The expression of EBS used in the protocol is likely to have other applications. In particular, it is well-suited to be promoted to an operator in non-perturbative loop quantum gravity.</description> <pubDate>2024-09-11</pubDate> <content:encoded><![CDATA[ Universe, Vol. 10, Pages 367: The Operational Meaning of Total Energy of Isolated Systems in General Relativity Universe <a href="https://www.mdpi.com/2218-1997/10/9/367">doi: 10.3390/universe10090367</a> Authors: Abhay Ashtekar Simone Speziale We present thought experiments to measure the Arnowitt&amp;ndash;Deser&amp;ndash;Misner EADM and Bondi&amp;ndash;Sachs energy EBS of isolated systems in general relativity. The expression of EBS used in the protocol is likely to have other applications. In particular, it is well-suited to be promoted to an operator in non-perturbative loop quantum gravity. ]]></content:encoded> <dc:title>The Operational Meaning of Total Energy of Isolated Systems in General Relativity</dc:title> <dc:creator>Abhay Ashtekar</dc:creator> <dc:creator>Simone Speziale</dc:creator> <dc:identifier>doi: 10.3390/universe10090367</dc:identifier> <dc:source>Universe</dc:source> <dc:date>2024-09-11</dc:date> <prism:publicationName>Universe</prism:publicationName> <prism:publicationDate>2024-09-11</prism:publicationDate> <prism:volume>10</prism:volume> <prism:number>9</prism:number> <prism:section>Article</prism:section> <prism:startingPage>367</prism:startingPage> <prism:doi>10.3390/universe10090367</prism:doi> <prism:url>https://www.mdpi.com/2218-1997/10/9/367</prism:url> <cc:license rdf:resource="CC BY 4.0"/> </item> <item rdf:about="https://www.mdpi.com/2218-1997/10/9/366"> <title>Universe, Vol. 10, Pages 366: Initial State in Quantum Cosmology and the Proper Mass of the Universe</title> <link>https://www.mdpi.com/2218-1997/10/9/366</link> <description>In the Euclidean form of the theory of gravity, where there is no dedicated time parameter, a generalized canonical form of the principle of least action is proposed. On its basis, the quantum principle of least action is formulated, in which the &amp;ldquo;dynamics&amp;rdquo; of the universe in the Origin is described by the eigenvector of the action operator&amp;mdash;the wave functional on the space of 4D Riemannian geometries and configurations of matter fields in some compact region of 4D space. The corresponding eigenvalue of the action operator determines the initial state for the world history of the universe outside this region, where the metric signature is Lorentzian and, thus, the time parameter exists. The boundary of the Origin region is determined by the condition that the rate of change of the determinant of the 3D metric tensor is zero on it. The size of the Origin is interpreted as a reciprocal temperature of the universe in the initial state. It has been suggested that in the initial state, the universe contains a certain distribution of its own mass, which is not directly related to the fields of matter.</description> <pubDate>2024-09-11</pubDate> <content:encoded><![CDATA[ Universe, Vol. 10, Pages 366: Initial State in Quantum Cosmology and the Proper Mass of the Universe Universe <a href="https://www.mdpi.com/2218-1997/10/9/366">doi: 10.3390/universe10090366</a> Authors: Natalia Gorobey Alexander Lukyanenko Alexander V. Goltsev In the Euclidean form of the theory of gravity, where there is no dedicated time parameter, a generalized canonical form of the principle of least action is proposed. On its basis, the quantum principle of least action is formulated, in which the &amp;ldquo;dynamics&amp;rdquo; of the universe in the Origin is described by the eigenvector of the action operator&amp;mdash;the wave functional on the space of 4D Riemannian geometries and configurations of matter fields in some compact region of 4D space. The corresponding eigenvalue of the action operator determines the initial state for the world history of the universe outside this region, where the metric signature is Lorentzian and, thus, the time parameter exists. The boundary of the Origin region is determined by the condition that the rate of change of the determinant of the 3D metric tensor is zero on it. The size of the Origin is interpreted as a reciprocal temperature of the universe in the initial state. It has been suggested that in the initial state, the universe contains a certain distribution of its own mass, which is not directly related to the fields of matter. ]]></content:encoded> <dc:title>Initial State in Quantum Cosmology and the Proper Mass of the Universe</dc:title> <dc:creator>Natalia Gorobey</dc:creator> <dc:creator>Alexander Lukyanenko</dc:creator> <dc:creator>Alexander V. Goltsev</dc:creator> <dc:identifier>doi: 10.3390/universe10090366</dc:identifier> <dc:source>Universe</dc:source> <dc:date>2024-09-11</dc:date> <prism:publicationName>Universe</prism:publicationName> <prism:publicationDate>2024-09-11</prism:publicationDate> <prism:volume>10</prism:volume> <prism:number>9</prism:number> <prism:section>Article</prism:section> <prism:startingPage>366</prism:startingPage> <prism:doi>10.3390/universe10090366</prism:doi> <prism:url>https://www.mdpi.com/2218-1997/10/9/366</prism:url> <cc:license rdf:resource="CC BY 4.0"/> </item> <item rdf:about="https://www.mdpi.com/2218-1997/10/9/365"> <title>Universe, Vol. 10, Pages 365: Comparing Analytic and Numerical Studies of Tensor Perturbations in Loop Quantum Cosmology</title> <link>https://www.mdpi.com/2218-1997/10/9/365</link> <description>We investigate the implications of different quantization approaches in Loop Quantum Cosmology for the primordial power spectrum of tensor modes. Specifically, we consider the hybrid and dressed metric approaches to derive the effective mass that governs the evolution of the tensor modes. Our study comprehensively examines the two resulting effective masses and how to estimate them in order to obtain approximated analytic solutions to the tensor perturbation equations. Since Loop Quantum Cosmology incorporates preinflationary effects in the dynamics of the perturbations, we do not have at our disposal a standard choice of privileged vacuum, like the Bunch&amp;ndash;Davies state in quasi-de Sitter inflation. We then select the vacuum state by a recently proposed criterion which removes unwanted oscillations in the power spectrum and guarantees an asymptotic diagonalization of the Hamiltonian in the ultraviolet. This vacuum is usually called the NO-AHD (from the initials of Non-Oscillating with Asymptotic Hamiltonian Diagonalization) vacuum. Consequently, we compute the power spectrum by using our analytic approximations and by introducing a suitable numerical procedure, adopting in both cases an NO-AHD vacuum. With this information, we compare the different spectra obtained from the hybrid and the dressed metric approaches, as well as from the analytic and numerical procedures. In particular, this proves the remarkable accuracy of our approximations.</description> <pubDate>2024-09-11</pubDate> <content:encoded><![CDATA[ Universe, Vol. 10, Pages 365: Comparing Analytic and Numerical Studies of Tensor Perturbations in Loop Quantum Cosmology Universe <a href="https://www.mdpi.com/2218-1997/10/9/365">doi: 10.3390/universe10090365</a> Authors: Guillermo A. Mena Marug谩n Antonio Vicente-Becerril Jes煤s Y茅bana Carrilero We investigate the implications of different quantization approaches in Loop Quantum Cosmology for the primordial power spectrum of tensor modes. Specifically, we consider the hybrid and dressed metric approaches to derive the effective mass that governs the evolution of the tensor modes. Our study comprehensively examines the two resulting effective masses and how to estimate them in order to obtain approximated analytic solutions to the tensor perturbation equations. Since Loop Quantum Cosmology incorporates preinflationary effects in the dynamics of the perturbations, we do not have at our disposal a standard choice of privileged vacuum, like the Bunch&amp;ndash;Davies state in quasi-de Sitter inflation. We then select the vacuum state by a recently proposed criterion which removes unwanted oscillations in the power spectrum and guarantees an asymptotic diagonalization of the Hamiltonian in the ultraviolet. This vacuum is usually called the NO-AHD (from the initials of Non-Oscillating with Asymptotic Hamiltonian Diagonalization) vacuum. Consequently, we compute the power spectrum by using our analytic approximations and by introducing a suitable numerical procedure, adopting in both cases an NO-AHD vacuum. With this information, we compare the different spectra obtained from the hybrid and the dressed metric approaches, as well as from the analytic and numerical procedures. In particular, this proves the remarkable accuracy of our approximations. ]]></content:encoded> <dc:title>Comparing Analytic and Numerical Studies of Tensor Perturbations in Loop Quantum Cosmology</dc:title> <dc:creator>Guillermo A. Mena Marug谩n</dc:creator> <dc:creator>Antonio Vicente-Becerril</dc:creator> <dc:creator>Jes煤s Y茅bana Carrilero</dc:creator> <dc:identifier>doi: 10.3390/universe10090365</dc:identifier> <dc:source>Universe</dc:source> <dc:date>2024-09-11</dc:date> <prism:publicationName>Universe</prism:publicationName> <prism:publicationDate>2024-09-11</prism:publicationDate> <prism:volume>10</prism:volume> <prism:number>9</prism:number> <prism:section>Article</prism:section> <prism:startingPage>365</prism:startingPage> <prism:doi>10.3390/universe10090365</prism:doi> <prism:url>https://www.mdpi.com/2218-1997/10/9/365</prism:url> <cc:license rdf:resource="CC BY 4.0"/> </item> <item rdf:about="https://www.mdpi.com/2218-1997/10/9/364"> <title>Universe, Vol. 10, Pages 364: Predicting Solar Cycles with a Parametric Time Series Model</title> <link>https://www.mdpi.com/2218-1997/10/9/364</link> <description>The objective of this paper is to reproduce and predict the series of solar cycle amplitudes using a simple time-series model that takes into account the variable time scale of the Gleissberg oscillation and the absence of clear evidence for odd&amp;ndash;even alternation prior to Solar Cycle 9 (SC9). It is demonstrated that the Gleissberg oscillation can be quite satisfactorily modelled as a sinusoidal variation of constant amplitude with a period increasing linearly with time. Subtracting this model from the actual cycle amplitudes, a clear even&amp;ndash;odd alternating pattern is discerned in the time series of the residuals since SC9. For this period of time, the mean value of the residuals for odd-numbered cycles is shown to exceed the value for even-numbered cycles by more than 4&amp;sigma;, providing the clearest evidence yet for a persistent odd&amp;ndash;even&amp;ndash;odd alternation in cycle amplitudes. Random deviations from these means are less than half the standard deviation of the raw cycle amplitude time series for the same period, which allows the use of these regularities for solar cycle prediction with substantially better confidence than the simple climatological average. Predicted cycle amplitudes are found to be robust against the addition or omission of some data points from the input set, and the method correctly hindcasts SC23 and SC24. The potential physical background of the regularities is also discussed. Our predictions for the amplitudes of SC25, SC26, and SC27 are 155.8&amp;plusmn;20.7, 96.9&amp;plusmn;25.1 and 140.8&amp;plusmn;20.7, respectively. This suggests that the amplitude of SC26 will be even lower than that of SC24, making it the weakest cycle since the Dalton Minimum.</description> <pubDate>2024-09-11</pubDate> <content:encoded><![CDATA[ Universe, Vol. 10, Pages 364: Predicting Solar Cycles with a Parametric Time Series Model Universe <a href="https://www.mdpi.com/2218-1997/10/9/364">doi: 10.3390/universe10090364</a> Authors: Kristof Petrovay The objective of this paper is to reproduce and predict the series of solar cycle amplitudes using a simple time-series model that takes into account the variable time scale of the Gleissberg oscillation and the absence of clear evidence for odd&amp;ndash;even alternation prior to Solar Cycle 9 (SC9). It is demonstrated that the Gleissberg oscillation can be quite satisfactorily modelled as a sinusoidal variation of constant amplitude with a period increasing linearly with time. Subtracting this model from the actual cycle amplitudes, a clear even&amp;ndash;odd alternating pattern is discerned in the time series of the residuals since SC9. For this period of time, the mean value of the residuals for odd-numbered cycles is shown to exceed the value for even-numbered cycles by more than 4&amp;sigma;, providing the clearest evidence yet for a persistent odd&amp;ndash;even&amp;ndash;odd alternation in cycle amplitudes. Random deviations from these means are less than half the standard deviation of the raw cycle amplitude time series for the same period, which allows the use of these regularities for solar cycle prediction with substantially better confidence than the simple climatological average. Predicted cycle amplitudes are found to be robust against the addition or omission of some data points from the input set, and the method correctly hindcasts SC23 and SC24. The potential physical background of the regularities is also discussed. Our predictions for the amplitudes of SC25, SC26, and SC27 are 155.8&amp;plusmn;20.7, 96.9&amp;plusmn;25.1 and 140.8&amp;plusmn;20.7, respectively. This suggests that the amplitude of SC26 will be even lower than that of SC24, making it the weakest cycle since the Dalton Minimum. ]]></content:encoded> <dc:title>Predicting Solar Cycles with a Parametric Time Series Model</dc:title> <dc:creator>Kristof Petrovay</dc:creator> <dc:identifier>doi: 10.3390/universe10090364</dc:identifier> <dc:source>Universe</dc:source> <dc:date>2024-09-11</dc:date> <prism:publicationName>Universe</prism:publicationName> <prism:publicationDate>2024-09-11</prism:publicationDate> <prism:volume>10</prism:volume> <prism:number>9</prism:number> <prism:section>Article</prism:section> <prism:startingPage>364</prism:startingPage> <prism:doi>10.3390/universe10090364</prism:doi> <prism:url>https://www.mdpi.com/2218-1997/10/9/364</prism:url> <cc:license rdf:resource="CC BY 4.0"/> </item> <item rdf:about="https://www.mdpi.com/2218-1997/10/9/363"> <title>Universe, Vol. 10, Pages 363: Ellipsoidal Universe and Cosmic Shear</title> <link>https://www.mdpi.com/2218-1997/10/9/363</link> <description>We consider a Bianchi I geometry of the universe. We obtain a cosmic shear expression related to the eccentricity of the universe. In particular, we study the connections among cosmic shear, eccentricity, and CMB. The equations are self-contained, with only two parameters.</description> <pubDate>2024-09-10</pubDate> <content:encoded><![CDATA[ Universe, Vol. 10, Pages 363: Ellipsoidal Universe and Cosmic Shear Universe <a href="https://www.mdpi.com/2218-1997/10/9/363">doi: 10.3390/universe10090363</a> Authors: Luigi Tedesco We consider a Bianchi I geometry of the universe. We obtain a cosmic shear expression related to the eccentricity of the universe. In particular, we study the connections among cosmic shear, eccentricity, and CMB. The equations are self-contained, with only two parameters. ]]></content:encoded> <dc:title>Ellipsoidal Universe and Cosmic Shear</dc:title> <dc:creator>Luigi Tedesco</dc:creator> <dc:identifier>doi: 10.3390/universe10090363</dc:identifier> <dc:source>Universe</dc:source> <dc:date>2024-09-10</dc:date> <prism:publicationName>Universe</prism:publicationName> <prism:publicationDate>2024-09-10</prism:publicationDate> <prism:volume>10</prism:volume> <prism:number>9</prism:number> <prism:section>Article</prism:section> <prism:startingPage>363</prism:startingPage> <prism:doi>10.3390/universe10090363</prism:doi> <prism:url>https://www.mdpi.com/2218-1997/10/9/363</prism:url> <cc:license rdf:resource="CC BY 4.0"/> </item> <item rdf:about="https://www.mdpi.com/2218-1997/10/9/362"> <title>Universe, Vol. 10, Pages 362: From de Sitter to de Sitter: A Thermal Approach to Running Vacuum Cosmology and the Non-Canonical Scalar Field Description</title> <link>https://www.mdpi.com/2218-1997/10/9/362</link> <description>The entire classical cosmological history between two extreme de Sitter vacuum solutions is discussed based on Einstein&amp;rsquo;s equations and non-equilibrium thermodynamics. The initial non-singular de Sitter state is characterised by a very high energy scale, which is equal or smaller than the reduced Planck mass. It is structurally unstable, and all of the continuous created matter, energy, and entropy of the material component comes from the irreversible flow powered by the primeval vacuum energy density. The analytical expression describing the running vacuum is obtained from the thermal approach. It opens a new perspective to solve the old puzzles and current observational challenges plaguing the cosmic concordance model driven by a rigid vacuum. Such a scenario is also modelled through a non-canonical scalar field. It is demonstrated that the resulting scalar field model is shown to be a step-by-step a faithful analytical representation of the thermal running vacuum cosmology.</description> <pubDate>2024-09-09</pubDate> <content:encoded><![CDATA[ Universe, Vol. 10, Pages 362: From de Sitter to de Sitter: A Thermal Approach to Running Vacuum Cosmology and the Non-Canonical Scalar Field Description Universe <a href="https://www.mdpi.com/2218-1997/10/9/362">doi: 10.3390/universe10090362</a> Authors: Pedro Eleuterio Mendon莽a Almeida Rose Clivia Santos Jose Ademir Sales Lima The entire classical cosmological history between two extreme de Sitter vacuum solutions is discussed based on Einstein&amp;rsquo;s equations and non-equilibrium thermodynamics. The initial non-singular de Sitter state is characterised by a very high energy scale, which is equal or smaller than the reduced Planck mass. It is structurally unstable, and all of the continuous created matter, energy, and entropy of the material component comes from the irreversible flow powered by the primeval vacuum energy density. The analytical expression describing the running vacuum is obtained from the thermal approach. It opens a new perspective to solve the old puzzles and current observational challenges plaguing the cosmic concordance model driven by a rigid vacuum. Such a scenario is also modelled through a non-canonical scalar field. It is demonstrated that the resulting scalar field model is shown to be a step-by-step a faithful analytical representation of the thermal running vacuum cosmology. ]]></content:encoded> <dc:title>From de Sitter to de Sitter: A Thermal Approach to Running Vacuum Cosmology and the Non-Canonical Scalar Field Description</dc:title> <dc:creator>Pedro Eleuterio Mendon莽a Almeida</dc:creator> <dc:creator>Rose Clivia Santos</dc:creator> <dc:creator>Jose Ademir Sales Lima</dc:creator> <dc:identifier>doi: 10.3390/universe10090362</dc:identifier> <dc:source>Universe</dc:source> <dc:date>2024-09-09</dc:date> <prism:publicationName>Universe</prism:publicationName> <prism:publicationDate>2024-09-09</prism:publicationDate> <prism:volume>10</prism:volume> <prism:number>9</prism:number> <prism:section>Article</prism:section> <prism:startingPage>362</prism:startingPage> <prism:doi>10.3390/universe10090362</prism:doi> <prism:url>https://www.mdpi.com/2218-1997/10/9/362</prism:url> <cc:license rdf:resource="CC BY 4.0"/> </item> <item rdf:about="https://www.mdpi.com/2218-1997/10/9/361"> <title>Universe, Vol. 10, Pages 361: On the Propagation of Gravitational Waves in the Weyl Invariant Theory of Gravity</title> <link>https://www.mdpi.com/2218-1997/10/9/361</link> <description>We revisit Weyl&amp;rsquo;s unified field theory, which arose in 1918, shortly after general relativity was discovered. As is well known, in order to extend the program of the geometrization of physics started by Einstein to include the electromagnetic field, H. Weyl developed a new geometry which constitutes a kind of generalization of Riemannian geometry. In this paper, our aim is to discuss Weyl&amp;rsquo;s proposal anew and examine its consistency and completeness as a physical theory. We propose new directions and possible conceptual changes in the original work. Among these, we investigate with some detail the propagation of gravitational waves, and the new features arising in this recent modified gravity theory, in which the presence of a massive vector field appears somewhat unexpectedly. We also speculate whether the results could be examined in the context of primordial gravitational waves.</description> <pubDate>2024-09-09</pubDate> <content:encoded><![CDATA[ Universe, Vol. 10, Pages 361: On the Propagation of Gravitational Waves in the Weyl Invariant Theory of Gravity Universe <a href="https://www.mdpi.com/2218-1997/10/9/361">doi: 10.3390/universe10090361</a> Authors: Mauro Duarte Fabio Dahia Carlos Romero We revisit Weyl&amp;rsquo;s unified field theory, which arose in 1918, shortly after general relativity was discovered. As is well known, in order to extend the program of the geometrization of physics started by Einstein to include the electromagnetic field, H. Weyl developed a new geometry which constitutes a kind of generalization of Riemannian geometry. In this paper, our aim is to discuss Weyl&amp;rsquo;s proposal anew and examine its consistency and completeness as a physical theory. We propose new directions and possible conceptual changes in the original work. Among these, we investigate with some detail the propagation of gravitational waves, and the new features arising in this recent modified gravity theory, in which the presence of a massive vector field appears somewhat unexpectedly. We also speculate whether the results could be examined in the context of primordial gravitational waves. ]]></content:encoded> <dc:title>On the Propagation of Gravitational Waves in the Weyl Invariant Theory of Gravity</dc:title> <dc:creator>Mauro Duarte</dc:creator> <dc:creator>Fabio Dahia</dc:creator> <dc:creator>Carlos Romero</dc:creator> <dc:identifier>doi: 10.3390/universe10090361</dc:identifier> <dc:source>Universe</dc:source> <dc:date>2024-09-09</dc:date> <prism:publicationName>Universe</prism:publicationName> <prism:publicationDate>2024-09-09</prism:publicationDate> <prism:volume>10</prism:volume> <prism:number>9</prism:number> <prism:section>Article</prism:section> <prism:startingPage>361</prism:startingPage> <prism:doi>10.3390/universe10090361</prism:doi> <prism:url>https://www.mdpi.com/2218-1997/10/9/361</prism:url> <cc:license rdf:resource="CC BY 4.0"/> </item> <item rdf:about="https://www.mdpi.com/2218-1997/10/9/360"> <title>Universe, Vol. 10, Pages 360: A Comprehensive Study on the Mid-Infrared Variability of Blazars</title> <link>https://www.mdpi.com/2218-1997/10/9/360</link> <description>We present a comprehensive investigation of mid-infrared (MIR) flux variability at 3.4 &amp;mu;m (W1 band) for a large sample of 3816 blazars, using Wide-field Infrared Survey Explorer (WISE) data through December 2022. The sample consists of 1740 flat-spectrum radio quasars (FSRQs), 1281 BL Lac objects (BL Lacs), and 795 blazars of uncertain type (BCUs). Considering Fermi Large Area Telescope detection, we classify 2331 as Fermi blazars and 1485 as non-Fermi blazars. Additionally, based on synchrotron peak frequency, the sample includes 2264 low-synchrotron peaked (LSP), 512 intermediate-synchrotron peaked (ISP), and 655 high-synchrotron peaked (HSP) sources. We conduct a comparative analysis of short- and long-term intrinsic variability amplitude (&amp;sigma;m), duty cycle (DC), and ensemble structure function (ESF) across blazar subclasses. The median short-term &amp;sigma;m values were 0.181&amp;minus;0.106+0.153, 0.104&amp;minus;0.054+0.101, 0.135&amp;minus;0.076+0.154, 0.173&amp;minus;0.097+0.158, 0.177&amp;minus;0.100+0.156, 0.096&amp;minus;0.050+0.109, and 0.106&amp;minus;0.058+0.100 mag for FSRQs, BL Lacs, Fermi blazars, non-Fermi blazars, LSPs, ISPs, and HSPs, respectively. The median DC values were 71.03&amp;minus;22.48+14.17, 64.02&amp;minus;22.86+16.97, 68.96&amp;minus;25.52+15.66, 69.40&amp;minus;22.17+14.42, 71.24&amp;minus;21.36+14.25, 63.03&amp;minus;33.19+16.93, and 64.63&amp;minus;24.26+15.88 percent for the same subclasses. The median long-term &amp;sigma;m values were 0.137&amp;minus;0.105+0.408, 0.171&amp;minus;0.132+0.206, 0.282&amp;minus;0.184+0.332, 0.071&amp;minus;0.062+0.143, 0.218&amp;minus;0.174+0.386, 0.173&amp;minus;0.132+0.208, and 0.101&amp;minus;0.077+0.161 mag for the same subclasses, respectively. Our results reveal significant differences in 3.4 &amp;mu;m flux variability among these subclasses. FSRQs (LSPs) exhibit larger &amp;sigma;m and DC values compared to BL Lacs (ISPs and HSPs). Fermi blazars display higher long-term &amp;sigma;m but lower short-term &amp;sigma;m relative to non-Fermi blazars, while DC distributions between the two groups are similar. ESF analysis further confirms the greater variability of FSRQs, LSPs, and Fermi blazars across a wide range of time scales compared to BL Lacs, ISPs/HSPs, and non-Fermi blazars. These findings highlight a close correlation between MIR variability and blazar properties, providing valuable insights into the underlying physical mechanisms responsible for their emission.</description> <pubDate>2024-09-07</pubDate> <content:encoded><![CDATA[ Universe, Vol. 10, Pages 360: A Comprehensive Study on the Mid-Infrared Variability of Blazars Universe <a href="https://www.mdpi.com/2218-1997/10/9/360">doi: 10.3390/universe10090360</a> Authors: Xuemei Zhang Zhipeng Hu Weitian Huang Lisheng Mao We present a comprehensive investigation of mid-infrared (MIR) flux variability at 3.4 &amp;mu;m (W1 band) for a large sample of 3816 blazars, using Wide-field Infrared Survey Explorer (WISE) data through December 2022. The sample consists of 1740 flat-spectrum radio quasars (FSRQs), 1281 BL Lac objects (BL Lacs), and 795 blazars of uncertain type (BCUs). Considering Fermi Large Area Telescope detection, we classify 2331 as Fermi blazars and 1485 as non-Fermi blazars. Additionally, based on synchrotron peak frequency, the sample includes 2264 low-synchrotron peaked (LSP), 512 intermediate-synchrotron peaked (ISP), and 655 high-synchrotron peaked (HSP) sources. We conduct a comparative analysis of short- and long-term intrinsic variability amplitude (&amp;sigma;m), duty cycle (DC), and ensemble structure function (ESF) across blazar subclasses. The median short-term &amp;sigma;m values were 0.181&amp;minus;0.106+0.153, 0.104&amp;minus;0.054+0.101, 0.135&amp;minus;0.076+0.154, 0.173&amp;minus;0.097+0.158, 0.177&amp;minus;0.100+0.156, 0.096&amp;minus;0.050+0.109, and 0.106&amp;minus;0.058+0.100 mag for FSRQs, BL Lacs, Fermi blazars, non-Fermi blazars, LSPs, ISPs, and HSPs, respectively. The median DC values were 71.03&amp;minus;22.48+14.17, 64.02&amp;minus;22.86+16.97, 68.96&amp;minus;25.52+15.66, 69.40&amp;minus;22.17+14.42, 71.24&amp;minus;21.36+14.25, 63.03&amp;minus;33.19+16.93, and 64.63&amp;minus;24.26+15.88 percent for the same subclasses. The median long-term &amp;sigma;m values were 0.137&amp;minus;0.105+0.408, 0.171&amp;minus;0.132+0.206, 0.282&amp;minus;0.184+0.332, 0.071&amp;minus;0.062+0.143, 0.218&amp;minus;0.174+0.386, 0.173&amp;minus;0.132+0.208, and 0.101&amp;minus;0.077+0.161 mag for the same subclasses, respectively. Our results reveal significant differences in 3.4 &amp;mu;m flux variability among these subclasses. FSRQs (LSPs) exhibit larger &amp;sigma;m and DC values compared to BL Lacs (ISPs and HSPs). Fermi blazars display higher long-term &amp;sigma;m but lower short-term &amp;sigma;m relative to non-Fermi blazars, while DC distributions between the two groups are similar. ESF analysis further confirms the greater variability of FSRQs, LSPs, and Fermi blazars across a wide range of time scales compared to BL Lacs, ISPs/HSPs, and non-Fermi blazars. These findings highlight a close correlation between MIR variability and blazar properties, providing valuable insights into the underlying physical mechanisms responsible for their emission. ]]></content:encoded> <dc:title>A Comprehensive Study on the Mid-Infrared Variability of Blazars</dc:title> <dc:creator>Xuemei Zhang</dc:creator> <dc:creator>Zhipeng Hu</dc:creator> <dc:creator>Weitian Huang</dc:creator> <dc:creator>Lisheng Mao</dc:creator> <dc:identifier>doi: 10.3390/universe10090360</dc:identifier> <dc:source>Universe</dc:source> <dc:date>2024-09-07</dc:date> <prism:publicationName>Universe</prism:publicationName> <prism:publicationDate>2024-09-07</prism:publicationDate> <prism:volume>10</prism:volume> <prism:number>9</prism:number> <prism:section>Article</prism:section> <prism:startingPage>360</prism:startingPage> <prism:doi>10.3390/universe10090360</prism:doi> <prism:url>https://www.mdpi.com/2218-1997/10/9/360</prism:url> <cc:license rdf:resource="CC BY 4.0"/> </item> <item rdf:about="https://www.mdpi.com/2218-1997/10/9/359"> <title>Universe, Vol. 10, Pages 359: Probing the Nonlinear Density Wave Theory of Spiral Galaxies by Baryonic Tully&ndash;Fisher Relation</title> <link>https://www.mdpi.com/2218-1997/10/9/359</link> <description>The baryonic mass&amp;ndash;velocity relation provides an important test of different galaxy dynamics models such as Lambda&amp;ndash;cold dark matter (&amp;Lambda;CDM) and alternatives like Modified Newtonian Dynamics (MOND). Novel nonlinear density wave theory with a soliton solution gives an opportunity to test whether the derived rotational velocity expression is able to support the well known Tully&amp;ndash;Fisher empirical relation between mass and rotation velocity in disk galaxies. Initial assumptions do not involve any larger dark matter halo that supports the stability of the very thin galactic disk nor any modified gravitational acceleration acting on galactic scales. It rather follows an important gravitational interaction between constituents of disk mass in the outer part of the disk via gravitational potential. Data are obtained by a fitting procedure applied on the sample of 81 rotational curves of late type spirals using expressions for the rotational velocity derived as an exact, a self-consistent solution of the nonlinear Schrodinger (NLS) equation for galactic surface mass density. The location of these selected objects in the baryonic mass&amp;ndash;rotation velocity plane follows the relation logMb=3.7&amp;plusmn;0.2logVflat+2.7&amp;plusmn;0.4 in marginal agreement with the findings in the literature.</description> <pubDate>2024-09-06</pubDate> <content:encoded><![CDATA[ Universe, Vol. 10, Pages 359: Probing the Nonlinear Density Wave Theory of Spiral Galaxies by Baryonic Tully&ndash;Fisher Relation Universe <a href="https://www.mdpi.com/2218-1997/10/9/359">doi: 10.3390/universe10090359</a> Authors: Miroslava Vukcevic Djordje Savic Predrag Jovanovi膰 The baryonic mass&amp;ndash;velocity relation provides an important test of different galaxy dynamics models such as Lambda&amp;ndash;cold dark matter (&amp;Lambda;CDM) and alternatives like Modified Newtonian Dynamics (MOND). Novel nonlinear density wave theory with a soliton solution gives an opportunity to test whether the derived rotational velocity expression is able to support the well known Tully&amp;ndash;Fisher empirical relation between mass and rotation velocity in disk galaxies. Initial assumptions do not involve any larger dark matter halo that supports the stability of the very thin galactic disk nor any modified gravitational acceleration acting on galactic scales. It rather follows an important gravitational interaction between constituents of disk mass in the outer part of the disk via gravitational potential. Data are obtained by a fitting procedure applied on the sample of 81 rotational curves of late type spirals using expressions for the rotational velocity derived as an exact, a self-consistent solution of the nonlinear Schrodinger (NLS) equation for galactic surface mass density. The location of these selected objects in the baryonic mass&amp;ndash;rotation velocity plane follows the relation logMb=3.7&amp;plusmn;0.2logVflat+2.7&amp;plusmn;0.4 in marginal agreement with the findings in the literature. ]]></content:encoded> <dc:title>Probing the Nonlinear Density Wave Theory of Spiral Galaxies by Baryonic Tully&amp;ndash;Fisher Relation</dc:title> <dc:creator>Miroslava Vukcevic</dc:creator> <dc:creator>Djordje Savic</dc:creator> <dc:creator>Predrag Jovanovi膰</dc:creator> <dc:identifier>doi: 10.3390/universe10090359</dc:identifier> <dc:source>Universe</dc:source> <dc:date>2024-09-06</dc:date> <prism:publicationName>Universe</prism:publicationName> <prism:publicationDate>2024-09-06</prism:publicationDate> <prism:volume>10</prism:volume> <prism:number>9</prism:number> <prism:section>Article</prism:section> <prism:startingPage>359</prism:startingPage> <prism:doi>10.3390/universe10090359</prism:doi> <prism:url>https://www.mdpi.com/2218-1997/10/9/359</prism:url> <cc:license rdf:resource="CC BY 4.0"/> </item> <item rdf:about="https://www.mdpi.com/2218-1997/10/9/358"> <title>Universe, Vol. 10, Pages 358: Three-Dimensional Quantum Black Holes: A Primer</title> <link>https://www.mdpi.com/2218-1997/10/9/358</link> <description>We review constructions of three-dimensional &amp;lsquo;quantum&amp;rsquo; black holes. Such spacetimes arise via holographic braneworlds and are exact solutions to an induced higher-derivative theory of gravity consistently coupled to a large-c quantum field theory with an ultraviolet cutoff, accounting for all orders of semi-classical backreaction. Notably, such quantum-corrected black holes are much larger than the Planck length. We describe the geometry and horizon thermodynamics of a host of asymptotically (anti-) de Sitter and flat quantum black holes. A summary of higher-dimensional extensions is given. We survey multiple applications of quantum black holes and braneworld holography.</description> <pubDate>2024-09-06</pubDate> <content:encoded><![CDATA[ Universe, Vol. 10, Pages 358: Three-Dimensional Quantum Black Holes: A Primer Universe <a href="https://www.mdpi.com/2218-1997/10/9/358">doi: 10.3390/universe10090358</a> Authors: Emanuele Panella Juan F. Pedraza Andrew Svesko We review constructions of three-dimensional &amp;lsquo;quantum&amp;rsquo; black holes. Such spacetimes arise via holographic braneworlds and are exact solutions to an induced higher-derivative theory of gravity consistently coupled to a large-c quantum field theory with an ultraviolet cutoff, accounting for all orders of semi-classical backreaction. Notably, such quantum-corrected black holes are much larger than the Planck length. We describe the geometry and horizon thermodynamics of a host of asymptotically (anti-) de Sitter and flat quantum black holes. A summary of higher-dimensional extensions is given. We survey multiple applications of quantum black holes and braneworld holography. ]]></content:encoded> <dc:title>Three-Dimensional Quantum Black Holes: A Primer</dc:title> <dc:creator>Emanuele Panella</dc:creator> <dc:creator>Juan F. Pedraza</dc:creator> <dc:creator>Andrew Svesko</dc:creator> <dc:identifier>doi: 10.3390/universe10090358</dc:identifier> <dc:source>Universe</dc:source> <dc:date>2024-09-06</dc:date> <prism:publicationName>Universe</prism:publicationName> <prism:publicationDate>2024-09-06</prism:publicationDate> <prism:volume>10</prism:volume> <prism:number>9</prism:number> <prism:section>Review</prism:section> <prism:startingPage>358</prism:startingPage> <prism:doi>10.3390/universe10090358</prism:doi> <prism:url>https://www.mdpi.com/2218-1997/10/9/358</prism:url> <cc:license rdf:resource="CC BY 4.0"/> </item> <item rdf:about="https://www.mdpi.com/2218-1997/10/9/357"> <title>Universe, Vol. 10, Pages 357: Exploring New Physics with Deep Underground Neutrino Experiment High-Energy Flux: The Case of Lorentz Invariance Violation, Large Extra Dimensions and Long-Range Forces</title> <link>https://www.mdpi.com/2218-1997/10/9/357</link> <description>DUNE is a next-generation long-baseline neutrino oscillation experiment. It is expected to measure, with unprecedented precision, the atmospheric oscillation parameters, including the CP-violating phase &amp;delta;CP. Moreover, several studies have suggested that its unique features should allow DUNE to probe several new physics scenarios. In this work, we explore the performances of the DUNE far detector in constraining new physics if a high-energy neutrino flux is employed (HE-DUNE). We take into account three different scenarios: Lorentz Invariance Violation (LIV), Long-Range Forces (LRFs) and Large Extra Dimensions (LEDs). Our results show that HE-DUNE should be able to set bounds competitive to the current ones and, in particular, it can outperform the standard DUNE capabilities in constraining CPT-even LIV parameters and the compactification radius RED of the LED model.</description> <pubDate>2024-09-05</pubDate> <content:encoded><![CDATA[ Universe, Vol. 10, Pages 357: Exploring New Physics with Deep Underground Neutrino Experiment High-Energy Flux: The Case of Lorentz Invariance Violation, Large Extra Dimensions and Long-Range Forces Universe <a href="https://www.mdpi.com/2218-1997/10/9/357">doi: 10.3390/universe10090357</a> Authors: Alessio Giarnetti Simone Marciano Davide Meloni DUNE is a next-generation long-baseline neutrino oscillation experiment. It is expected to measure, with unprecedented precision, the atmospheric oscillation parameters, including the CP-violating phase &amp;delta;CP. Moreover, several studies have suggested that its unique features should allow DUNE to probe several new physics scenarios. In this work, we explore the performances of the DUNE far detector in constraining new physics if a high-energy neutrino flux is employed (HE-DUNE). We take into account three different scenarios: Lorentz Invariance Violation (LIV), Long-Range Forces (LRFs) and Large Extra Dimensions (LEDs). Our results show that HE-DUNE should be able to set bounds competitive to the current ones and, in particular, it can outperform the standard DUNE capabilities in constraining CPT-even LIV parameters and the compactification radius RED of the LED model. ]]></content:encoded> <dc:title>Exploring New Physics with Deep Underground Neutrino Experiment High-Energy Flux: The Case of Lorentz Invariance Violation, Large Extra Dimensions and Long-Range Forces</dc:title> <dc:creator>Alessio Giarnetti</dc:creator> <dc:creator>Simone Marciano</dc:creator> <dc:creator>Davide Meloni</dc:creator> <dc:identifier>doi: 10.3390/universe10090357</dc:identifier> <dc:source>Universe</dc:source> <dc:date>2024-09-05</dc:date> <prism:publicationName>Universe</prism:publicationName> <prism:publicationDate>2024-09-05</prism:publicationDate> <prism:volume>10</prism:volume> <prism:number>9</prism:number> <prism:section>Article</prism:section> <prism:startingPage>357</prism:startingPage> <prism:doi>10.3390/universe10090357</prism:doi> <prism:url>https://www.mdpi.com/2218-1997/10/9/357</prism:url> <cc:license rdf:resource="CC BY 4.0"/> </item> <item rdf:about="https://www.mdpi.com/2218-1997/10/9/356"> <title>Universe, Vol. 10, Pages 356: Non-Canonical Dark Energy Parameter Evolution in a Canonical Quintessence Cosmology</title> <link>https://www.mdpi.com/2218-1997/10/9/356</link> <description>This study considers the specific case of a flat, minimally coupled to gravity, quintessence cosmology with a dark energy quartic polynomial potential that has the same mathematical form as the Higgs potential. Previous work on this case determined that the scalar field is given by a simple expression of the Lambert W function in terms of the easily observable scale factor. This expression provides analytic equations for the evolution of cosmological dark energy parameters as a function of the scale factor for all points on the Lambert W function principal branch. The Lambert W function is zero at a scale factor of zero that marks the big bang. The evolutionary equations beyond the big bang describe a canonical universe that is similar to &amp;Lambda;CDM, making it an excellent dynamical template to compare with observational data. The portion of the W function principal before the big bang extends to the infinite pre-bang past. It describes a noncanonical universe with an initially very low mass density that contracts by rolling down the dark energy potential to a singularity, big bang, at the scale factor zero point. This provides a natural origin for the big bang. It also raises the possibility that the universe existed before the big bang and is far older, and that it was once far larger than its current size. The recent increasing interest in the possibility of a dynamical universe instead of &amp;Lambda;CDM makes the exploration of the nature of such universes particularly relevant.</description> <pubDate>2024-09-05</pubDate> <content:encoded><![CDATA[ Universe, Vol. 10, Pages 356: Non-Canonical Dark Energy Parameter Evolution in a Canonical Quintessence Cosmology Universe <a href="https://www.mdpi.com/2218-1997/10/9/356">doi: 10.3390/universe10090356</a> Authors: Rodger I. Thompson This study considers the specific case of a flat, minimally coupled to gravity, quintessence cosmology with a dark energy quartic polynomial potential that has the same mathematical form as the Higgs potential. Previous work on this case determined that the scalar field is given by a simple expression of the Lambert W function in terms of the easily observable scale factor. This expression provides analytic equations for the evolution of cosmological dark energy parameters as a function of the scale factor for all points on the Lambert W function principal branch. The Lambert W function is zero at a scale factor of zero that marks the big bang. The evolutionary equations beyond the big bang describe a canonical universe that is similar to &amp;Lambda;CDM, making it an excellent dynamical template to compare with observational data. The portion of the W function principal before the big bang extends to the infinite pre-bang past. It describes a noncanonical universe with an initially very low mass density that contracts by rolling down the dark energy potential to a singularity, big bang, at the scale factor zero point. This provides a natural origin for the big bang. It also raises the possibility that the universe existed before the big bang and is far older, and that it was once far larger than its current size. The recent increasing interest in the possibility of a dynamical universe instead of &amp;Lambda;CDM makes the exploration of the nature of such universes particularly relevant. ]]></content:encoded> <dc:title>Non-Canonical Dark Energy Parameter Evolution in a Canonical Quintessence Cosmology</dc:title> <dc:creator>Rodger I. Thompson</dc:creator> <dc:identifier>doi: 10.3390/universe10090356</dc:identifier> <dc:source>Universe</dc:source> <dc:date>2024-09-05</dc:date> <prism:publicationName>Universe</prism:publicationName> <prism:publicationDate>2024-09-05</prism:publicationDate> <prism:volume>10</prism:volume> <prism:number>9</prism:number> <prism:section>Article</prism:section> <prism:startingPage>356</prism:startingPage> <prism:doi>10.3390/universe10090356</prism:doi> <prism:url>https://www.mdpi.com/2218-1997/10/9/356</prism:url> <cc:license rdf:resource="CC BY 4.0"/> </item> <item rdf:about="https://www.mdpi.com/2218-1997/10/9/355"> <title>Universe, Vol. 10, Pages 355: 4D Embedded Rotating Black Hole as a Particle Accelerator in the Presence of Magnetic Fields</title> <link>https://www.mdpi.com/2218-1997/10/9/355</link> <description>We analyze a rotating black hole (BH) in a four-dimensional space-time embedded in five-dimensional flat bulk. In Boyer&amp;ndash;Lindquist coordinates, we use a generic extension of the Kerr metric by the line element of G&amp;uuml;rses&amp;ndash;G&amp;uuml;rsey metric. We discuss their horizon properties and shadow cast which is tailored by the influence of the extrinsic curvature. By means of the model based on the Nash&amp;ndash;Greene theorem, we analyze the G&amp;uuml;rses&amp;ndash;G&amp;uuml;rsey metric embedded in five dimensions acting as a rotating &amp;ldquo;charged&amp;rdquo; BH which may be regarded as a source of ultrahigh-energy cosmic rays (UHECRs). We also show that this type of BH presents a different structure of the accretion disk which is modified by the extrinsic curvature leading to an enlargement of the photons ring and an increase in the BH&amp;rsquo;s inner shadow. In the presence of a magnetic field, our initial results suggest that such BHs may be efficient free-test particle accelerators orbiting the inner stable circular orbit (ISCO).</description> <pubDate>2024-09-04</pubDate> <content:encoded><![CDATA[ Universe, Vol. 10, Pages 355: 4D Embedded Rotating Black Hole as a Particle Accelerator in the Presence of Magnetic Fields Universe <a href="https://www.mdpi.com/2218-1997/10/9/355">doi: 10.3390/universe10090355</a> Authors: Abra茫o J. S. Capistrano Carlos Henrique Coimbra-Ara煤jo Rita de C谩ssia dos Anjos We analyze a rotating black hole (BH) in a four-dimensional space-time embedded in five-dimensional flat bulk. In Boyer&amp;ndash;Lindquist coordinates, we use a generic extension of the Kerr metric by the line element of G&amp;uuml;rses&amp;ndash;G&amp;uuml;rsey metric. We discuss their horizon properties and shadow cast which is tailored by the influence of the extrinsic curvature. By means of the model based on the Nash&amp;ndash;Greene theorem, we analyze the G&amp;uuml;rses&amp;ndash;G&amp;uuml;rsey metric embedded in five dimensions acting as a rotating &amp;ldquo;charged&amp;rdquo; BH which may be regarded as a source of ultrahigh-energy cosmic rays (UHECRs). We also show that this type of BH presents a different structure of the accretion disk which is modified by the extrinsic curvature leading to an enlargement of the photons ring and an increase in the BH&amp;rsquo;s inner shadow. In the presence of a magnetic field, our initial results suggest that such BHs may be efficient free-test particle accelerators orbiting the inner stable circular orbit (ISCO). ]]></content:encoded> <dc:title>4D Embedded Rotating Black Hole as a Particle Accelerator in the Presence of Magnetic Fields</dc:title> <dc:creator>Abra茫o J. S. Capistrano</dc:creator> <dc:creator>Carlos Henrique Coimbra-Ara煤jo</dc:creator> <dc:creator>Rita de C谩ssia dos Anjos</dc:creator> <dc:identifier>doi: 10.3390/universe10090355</dc:identifier> <dc:source>Universe</dc:source> <dc:date>2024-09-04</dc:date> <prism:publicationName>Universe</prism:publicationName> <prism:publicationDate>2024-09-04</prism:publicationDate> <prism:volume>10</prism:volume> <prism:number>9</prism:number> <prism:section>Article</prism:section> <prism:startingPage>355</prism:startingPage> <prism:doi>10.3390/universe10090355</prism:doi> <prism:url>https://www.mdpi.com/2218-1997/10/9/355</prism:url> <cc:license rdf:resource="CC BY 4.0"/> </item> <item rdf:about="https://www.mdpi.com/2218-1997/10/9/354"> <title>Universe, Vol. 10, Pages 354: Quantum Loop Corrections in the Modified Gravity Model of Starobinsky Inflation with Primordial Black Hole Production</title> <link>https://www.mdpi.com/2218-1997/10/9/354</link> <description>A modified gravity model of Starobinsky inflation and primordial black hole production is proposed in good (within 1&amp;sigma;) agreement with current measurements of the cosmic microwave background radiation. The model is an extension of the singularity-free Appleby&amp;ndash;Battye&amp;ndash;Starobinsky model by the R4 term with different values of the parameters whose fine-tuning leads to the efficient production of primordial black holes on smaller scales with the asteroid-size masses between 1016 g and 1020 g. Those primordial black holes may be part (or the whole) of the current dark matter, while the proposed model can be confirmed or falsified by the detection or absence of the induced gravitational waves with the frequencies in the 10&amp;minus;2 Hz range. The relative size of quantum (loop) corrections to the power spectrum of scalar perturbations in the model is found to be of the order of 10&amp;minus;3 or less, so that the model is not ruled out by the quantum corrections.</description> <pubDate>2024-09-04</pubDate> <content:encoded><![CDATA[ Universe, Vol. 10, Pages 354: Quantum Loop Corrections in the Modified Gravity Model of Starobinsky Inflation with Primordial Black Hole Production Universe <a href="https://www.mdpi.com/2218-1997/10/9/354">doi: 10.3390/universe10090354</a> Authors: Sultan Saburov Sergei V. Ketov A modified gravity model of Starobinsky inflation and primordial black hole production is proposed in good (within 1&amp;sigma;) agreement with current measurements of the cosmic microwave background radiation. The model is an extension of the singularity-free Appleby&amp;ndash;Battye&amp;ndash;Starobinsky model by the R4 term with different values of the parameters whose fine-tuning leads to the efficient production of primordial black holes on smaller scales with the asteroid-size masses between 1016 g and 1020 g. Those primordial black holes may be part (or the whole) of the current dark matter, while the proposed model can be confirmed or falsified by the detection or absence of the induced gravitational waves with the frequencies in the 10&amp;minus;2 Hz range. The relative size of quantum (loop) corrections to the power spectrum of scalar perturbations in the model is found to be of the order of 10&amp;minus;3 or less, so that the model is not ruled out by the quantum corrections. ]]></content:encoded> <dc:title>Quantum Loop Corrections in the Modified Gravity Model of Starobinsky Inflation with Primordial Black Hole Production</dc:title> <dc:creator>Sultan Saburov</dc:creator> <dc:creator>Sergei V. Ketov</dc:creator> <dc:identifier>doi: 10.3390/universe10090354</dc:identifier> <dc:source>Universe</dc:source> <dc:date>2024-09-04</dc:date> <prism:publicationName>Universe</prism:publicationName> <prism:publicationDate>2024-09-04</prism:publicationDate> <prism:volume>10</prism:volume> <prism:number>9</prism:number> <prism:section>Article</prism:section> <prism:startingPage>354</prism:startingPage> <prism:doi>10.3390/universe10090354</prism:doi> <prism:url>https://www.mdpi.com/2218-1997/10/9/354</prism:url> <cc:license rdf:resource="CC BY 4.0"/> </item> <item rdf:about="https://www.mdpi.com/2218-1997/10/9/353"> <title>Universe, Vol. 10, Pages 353: Combined Studies Approach to Rule Out Cosmological Models Which Are Based on Nonlinear Electrodynamics</title> <link>https://www.mdpi.com/2218-1997/10/9/353</link> <description>We apply a combined study in order to investigate the dynamics of cosmological models incorporating nonlinear electrodynamics (NLED). The study is based on the simultaneous investigation of such fundamental aspects as stability and causality, complemented with a dynamical systems investigation of the involved models, as well as Bayesian inference for parameter estimation. We explore two specific NLED models: the power-law and the rational Lagrangian. We present the theoretical framework of NLED coupled with general relativity, followed by an analysis of the stability and causality of the various NLED Lagrangians. We then perform a detailed dynamical analysis to identify the ranges where these models are stable and causal. Our results show that the power-law Lagrangian model transitions through various cosmological phases, evolving from a Maxwell radiation-dominated state to a matter-dominated state. For the rational Lagrangian model, including the Maxwell term, stable and causal behavior is observed within specific parameter ranges, with critical points indicating the evolutionary pathways of the universe. To validate our theoretical findings, we perform Bayesian parameter estimation using a comprehensive set of observational data, including cosmic chronometers, baryon acoustic oscillation (BAO) measurements, and supernovae type Ia (SNeIa). The estimated parameters for both models align with the expected values for the current universe, particularly the matter density &amp;Omega;m and the Hubble parameter h. However, the parameters of the models are not tightly constrained within the prior ranges. Our combined studies approach rules out the mentioned models as an appropriate description of the cosmos. Our results highlight the need for further refinement and exploration of NLED-based cosmological models to fully integrate them into the standard cosmological framework.</description> <pubDate>2024-09-04</pubDate> <content:encoded><![CDATA[ Universe, Vol. 10, Pages 353: Combined Studies Approach to Rule Out Cosmological Models Which Are Based on Nonlinear Electrodynamics Universe <a href="https://www.mdpi.com/2218-1997/10/9/353">doi: 10.3390/universe10090353</a> Authors: Ricardo Garc铆a-Salcedo Isidro G贸mez-Vargas Tame Gonz谩lez Vicent Martinez-Badenes Israel Quiros We apply a combined study in order to investigate the dynamics of cosmological models incorporating nonlinear electrodynamics (NLED). The study is based on the simultaneous investigation of such fundamental aspects as stability and causality, complemented with a dynamical systems investigation of the involved models, as well as Bayesian inference for parameter estimation. We explore two specific NLED models: the power-law and the rational Lagrangian. We present the theoretical framework of NLED coupled with general relativity, followed by an analysis of the stability and causality of the various NLED Lagrangians. We then perform a detailed dynamical analysis to identify the ranges where these models are stable and causal. Our results show that the power-law Lagrangian model transitions through various cosmological phases, evolving from a Maxwell radiation-dominated state to a matter-dominated state. For the rational Lagrangian model, including the Maxwell term, stable and causal behavior is observed within specific parameter ranges, with critical points indicating the evolutionary pathways of the universe. To validate our theoretical findings, we perform Bayesian parameter estimation using a comprehensive set of observational data, including cosmic chronometers, baryon acoustic oscillation (BAO) measurements, and supernovae type Ia (SNeIa). The estimated parameters for both models align with the expected values for the current universe, particularly the matter density &amp;Omega;m and the Hubble parameter h. However, the parameters of the models are not tightly constrained within the prior ranges. Our combined studies approach rules out the mentioned models as an appropriate description of the cosmos. Our results highlight the need for further refinement and exploration of NLED-based cosmological models to fully integrate them into the standard cosmological framework. ]]></content:encoded> <dc:title>Combined Studies Approach to Rule Out Cosmological Models Which Are Based on Nonlinear Electrodynamics</dc:title> <dc:creator>Ricardo Garc铆a-Salcedo</dc:creator> <dc:creator>Isidro G贸mez-Vargas</dc:creator> <dc:creator>Tame Gonz谩lez</dc:creator> <dc:creator>Vicent Martinez-Badenes</dc:creator> <dc:creator>Israel Quiros</dc:creator> <dc:identifier>doi: 10.3390/universe10090353</dc:identifier> <dc:source>Universe</dc:source> <dc:date>2024-09-04</dc:date> <prism:publicationName>Universe</prism:publicationName> <prism:publicationDate>2024-09-04</prism:publicationDate> <prism:volume>10</prism:volume> <prism:number>9</prism:number> <prism:section>Article</prism:section> <prism:startingPage>353</prism:startingPage> <prism:doi>10.3390/universe10090353</prism:doi> <prism:url>https://www.mdpi.com/2218-1997/10/9/353</prism:url> <cc:license rdf:resource="CC BY 4.0"/> </item> <item rdf:about="https://www.mdpi.com/2218-1997/10/9/352"> <title>Universe, Vol. 10, Pages 352: Different Aspects of Entropic Cosmology</title> <link>https://www.mdpi.com/2218-1997/10/9/352</link> <description>We provide a short review of the recent developments in entropic cosmology based on two thermodynamic laws of the apparent horizon, namely the first and the second laws of thermodynamics. The first law essentially provides the change in entropy of the apparent horizon during the cosmic evolution of the universe; in particular, it is expressed by TdS=&amp;minus;d(&amp;rho;V)+WdV (where W is the work density and other quantities have their usual meanings). In this way, the first law actually links various theories of gravity with the entropy of the apparent horizon. This leads to a natural question&amp;mdash;&amp;ldquo;What is the form of the horizon entropy corresponding to a general modified theory of gravity?&amp;rdquo;. The second law of horizon thermodynamics states that the change in total entropy (the sum of horizon entropy + matter fields&amp;rsquo; entropy) with respect to cosmic time must be positive, where the matter fields behave like an open system characterised by a non-zero chemical potential. The second law of horizon thermodynamics importantly provides model-independent constraints on entropic parameters. Finally, we discuss the standpoint of entropic cosmology on inflation (or bounce), reheating and primordial gravitational waves from the perspective of a generalised entropy function.</description> <pubDate>2024-09-03</pubDate> <content:encoded><![CDATA[ Universe, Vol. 10, Pages 352: Different Aspects of Entropic Cosmology Universe <a href="https://www.mdpi.com/2218-1997/10/9/352">doi: 10.3390/universe10090352</a> Authors: Shin鈥檌chi Nojiri Sergei D. Odintsov Tanmoy Paul We provide a short review of the recent developments in entropic cosmology based on two thermodynamic laws of the apparent horizon, namely the first and the second laws of thermodynamics. The first law essentially provides the change in entropy of the apparent horizon during the cosmic evolution of the universe; in particular, it is expressed by TdS=&amp;minus;d(&amp;rho;V)+WdV (where W is the work density and other quantities have their usual meanings). In this way, the first law actually links various theories of gravity with the entropy of the apparent horizon. This leads to a natural question&amp;mdash;&amp;ldquo;What is the form of the horizon entropy corresponding to a general modified theory of gravity?&amp;rdquo;. The second law of horizon thermodynamics states that the change in total entropy (the sum of horizon entropy + matter fields&amp;rsquo; entropy) with respect to cosmic time must be positive, where the matter fields behave like an open system characterised by a non-zero chemical potential. The second law of horizon thermodynamics importantly provides model-independent constraints on entropic parameters. Finally, we discuss the standpoint of entropic cosmology on inflation (or bounce), reheating and primordial gravitational waves from the perspective of a generalised entropy function. ]]></content:encoded> <dc:title>Different Aspects of Entropic Cosmology</dc:title> <dc:creator>Shin鈥檌chi Nojiri</dc:creator> <dc:creator>Sergei D. Odintsov</dc:creator> <dc:creator>Tanmoy Paul</dc:creator> <dc:identifier>doi: 10.3390/universe10090352</dc:identifier> <dc:source>Universe</dc:source> <dc:date>2024-09-03</dc:date> <prism:publicationName>Universe</prism:publicationName> <prism:publicationDate>2024-09-03</prism:publicationDate> <prism:volume>10</prism:volume> <prism:number>9</prism:number> <prism:section>Review</prism:section> <prism:startingPage>352</prism:startingPage> <prism:doi>10.3390/universe10090352</prism:doi> <prism:url>https://www.mdpi.com/2218-1997/10/9/352</prism:url> <cc:license rdf:resource="CC BY 4.0"/> </item> <item rdf:about="https://www.mdpi.com/2218-1997/10/9/351"> <title>Universe, Vol. 10, Pages 351: On the Classical Limit of Freely Falling Quantum Particles, Quantum Corrections and the Emergence of the Equivalence Principle</title> <link>https://www.mdpi.com/2218-1997/10/9/351</link> <description>Quantum and classical mechanics are fundamentally different theories, but the correspondence principle states that quantum particles behave classically in the appropriate limit. For high-energy periodic quantum systems, the emergence of the classical description should be understood in a distributional sense, i.e., the quantum probability density approaches the classical distribution when the former is coarse-grained. Following a simple reformulation of this limit in the Fourier space, in this paper, we investigate the macroscopic behavior of freely falling quantum particles. To illustrate how the method works and to fix some ideas, we first successfully apply it to the case of a particle in a box. Next, we show that, for a particle bouncing under the gravity field, in the limit of a high quantum number, the leading term of the quantum distribution corresponds to the exact classical distribution plus sub-leading corrections, which we interpret as quantum corrections at the macroscopic level.</description> <pubDate>2024-09-02</pubDate> <content:encoded><![CDATA[ Universe, Vol. 10, Pages 351: On the Classical Limit of Freely Falling Quantum Particles, Quantum Corrections and the Emergence of the Equivalence Principle Universe <a href="https://www.mdpi.com/2218-1997/10/9/351">doi: 10.3390/universe10090351</a> Authors: Juan A. Ca帽as J. Bernal A. Mart铆n-Ruiz Quantum and classical mechanics are fundamentally different theories, but the correspondence principle states that quantum particles behave classically in the appropriate limit. For high-energy periodic quantum systems, the emergence of the classical description should be understood in a distributional sense, i.e., the quantum probability density approaches the classical distribution when the former is coarse-grained. Following a simple reformulation of this limit in the Fourier space, in this paper, we investigate the macroscopic behavior of freely falling quantum particles. To illustrate how the method works and to fix some ideas, we first successfully apply it to the case of a particle in a box. Next, we show that, for a particle bouncing under the gravity field, in the limit of a high quantum number, the leading term of the quantum distribution corresponds to the exact classical distribution plus sub-leading corrections, which we interpret as quantum corrections at the macroscopic level. ]]></content:encoded> <dc:title>On the Classical Limit of Freely Falling Quantum Particles, Quantum Corrections and the Emergence of the Equivalence Principle</dc:title> <dc:creator>Juan A. Ca帽as</dc:creator> <dc:creator>J. Bernal</dc:creator> <dc:creator>A. Mart铆n-Ruiz</dc:creator> <dc:identifier>doi: 10.3390/universe10090351</dc:identifier> <dc:source>Universe</dc:source> <dc:date>2024-09-02</dc:date> <prism:publicationName>Universe</prism:publicationName> <prism:publicationDate>2024-09-02</prism:publicationDate> <prism:volume>10</prism:volume> <prism:number>9</prism:number> <prism:section>Article</prism:section> <prism:startingPage>351</prism:startingPage> <prism:doi>10.3390/universe10090351</prism:doi> <prism:url>https://www.mdpi.com/2218-1997/10/9/351</prism:url> <cc:license rdf:resource="CC BY 4.0"/> </item> <item rdf:about="https://www.mdpi.com/2218-1997/10/9/350"> <title>Universe, Vol. 10, Pages 350: About Jordan and Einstein Frames: A Study in Inflationary Magnetogenesis</title> <link>https://www.mdpi.com/2218-1997/10/9/350</link> <description>In this paper, we make a detailed side-by-side comparison between Jordan and Einstein frames in the context of cosmic magnetogenesis. We have computed the evolution of the vector potential in each frame along with some observables such as the spectral index and the magnetic field amplitude. We found that contrary to the Einstein frame, the electric and magnetic energy densities in the Jordan Frame do not depend on any parameter associated with the scalar field. Furthermore, in the Einstein frame, and assuming scale invariance for the magnetic field, most of the total energy density contribution comes from the electric and magnetic densities. Finally, we show the ratio between magnetic field signals in both frames printed in the CMB.</description> <pubDate>2024-09-01</pubDate> <content:encoded><![CDATA[ Universe, Vol. 10, Pages 350: About Jordan and Einstein Frames: A Study in Inflationary Magnetogenesis Universe <a href="https://www.mdpi.com/2218-1997/10/9/350">doi: 10.3390/universe10090350</a> Authors: Joel Vel谩squez H茅ctor J. Hortua Leonardo Casta帽eda In this paper, we make a detailed side-by-side comparison between Jordan and Einstein frames in the context of cosmic magnetogenesis. We have computed the evolution of the vector potential in each frame along with some observables such as the spectral index and the magnetic field amplitude. We found that contrary to the Einstein frame, the electric and magnetic energy densities in the Jordan Frame do not depend on any parameter associated with the scalar field. Furthermore, in the Einstein frame, and assuming scale invariance for the magnetic field, most of the total energy density contribution comes from the electric and magnetic densities. Finally, we show the ratio between magnetic field signals in both frames printed in the CMB. ]]></content:encoded> <dc:title>About Jordan and Einstein Frames: A Study in Inflationary Magnetogenesis</dc:title> <dc:creator>Joel Vel谩squez</dc:creator> <dc:creator>H茅ctor J. Hortua</dc:creator> <dc:creator>Leonardo Casta帽eda</dc:creator> <dc:identifier>doi: 10.3390/universe10090350</dc:identifier> <dc:source>Universe</dc:source> <dc:date>2024-09-01</dc:date> <prism:publicationName>Universe</prism:publicationName> <prism:publicationDate>2024-09-01</prism:publicationDate> <prism:volume>10</prism:volume> <prism:number>9</prism:number> <prism:section>Article</prism:section> <prism:startingPage>350</prism:startingPage> <prism:doi>10.3390/universe10090350</prism:doi> <prism:url>https://www.mdpi.com/2218-1997/10/9/350</prism:url> <cc:license rdf:resource="CC BY 4.0"/> </item> <item rdf:about="https://www.mdpi.com/2218-1997/10/9/349"> <title>Universe, Vol. 10, Pages 349: Characterisation of the Atmosphere in Very High Energy Gamma-Astronomy for Imaging Atmospheric Cherenkov Telescopes</title> <link>https://www.mdpi.com/2218-1997/10/9/349</link> <description>Ground-based observations of Very High Energy (VHE) gamma rays from extreme astrophysical sources are significantly influenced by atmospheric conditions. This is due to the atmosphere being an integral part of the detector when utilizing Imaging Atmospheric Cherenkov Telescopes (IACTs). Clouds and dust particles diminish atmospheric transmission of Cherenkov light, thereby impacting the reconstruction of the air showers and consequently the reconstructed gamma-ray spectra. Precise measurements of atmospheric transmission above Cherenkov observatories play a pivotal role in the accuracy of the analysed data, among which the corrections of the reconstructed energies and fluxes of incoming gamma rays, and in establishing observation strategies for different types of gamma-ray emitting sources. The Major Atmospheric Gamma Imaging Cherenkov (MAGIC) telescopes and the Cherenkov Telescope Array Observatory (CTAO), both located on the Observatorio del Roque de los Muchachos (ORM), La Palma, Canary Islands, use different sets of auxiliary instruments for real-time characterisation of the atmosphere. In this paper, historical data taken by MAGIC LIDAR (LIght Detection And Ranging) and CTAO FRAM (F/Photometric Robotic Telescope) are presented. From the atmospheric aerosol transmission profiles measured by the MAGIC LIDAR and CTAO FRAM aerosol optical depth maps, we obtain the characterisation of the clouds above the ORM at La Palma needed for data correction and optimal observation scheduling.</description> <pubDate>2024-08-30</pubDate> <content:encoded><![CDATA[ Universe, Vol. 10, Pages 349: Characterisation of the Atmosphere in Very High Energy Gamma-Astronomy for Imaging Atmospheric Cherenkov Telescopes Universe <a href="https://www.mdpi.com/2218-1997/10/9/349">doi: 10.3390/universe10090349</a> Authors: Dijana Dominis Prester Jan Ebr Markus Gaug Alexander Hahn Ana Babi膰 Ji艡铆 Eli谩拧ek Petr Jane膷ek Sergey Karpov Marta Kolarek Marina Manganaro Razmik Mirzoyan Ground-based observations of Very High Energy (VHE) gamma rays from extreme astrophysical sources are significantly influenced by atmospheric conditions. This is due to the atmosphere being an integral part of the detector when utilizing Imaging Atmospheric Cherenkov Telescopes (IACTs). Clouds and dust particles diminish atmospheric transmission of Cherenkov light, thereby impacting the reconstruction of the air showers and consequently the reconstructed gamma-ray spectra. Precise measurements of atmospheric transmission above Cherenkov observatories play a pivotal role in the accuracy of the analysed data, among which the corrections of the reconstructed energies and fluxes of incoming gamma rays, and in establishing observation strategies for different types of gamma-ray emitting sources. The Major Atmospheric Gamma Imaging Cherenkov (MAGIC) telescopes and the Cherenkov Telescope Array Observatory (CTAO), both located on the Observatorio del Roque de los Muchachos (ORM), La Palma, Canary Islands, use different sets of auxiliary instruments for real-time characterisation of the atmosphere. In this paper, historical data taken by MAGIC LIDAR (LIght Detection And Ranging) and CTAO FRAM (F/Photometric Robotic Telescope) are presented. From the atmospheric aerosol transmission profiles measured by the MAGIC LIDAR and CTAO FRAM aerosol optical depth maps, we obtain the characterisation of the clouds above the ORM at La Palma needed for data correction and optimal observation scheduling. ]]></content:encoded> <dc:title>Characterisation of the Atmosphere in Very High Energy Gamma-Astronomy for Imaging Atmospheric Cherenkov Telescopes</dc:title> <dc:creator>Dijana Dominis Prester</dc:creator> <dc:creator>Jan Ebr</dc:creator> <dc:creator>Markus Gaug</dc:creator> <dc:creator>Alexander Hahn</dc:creator> <dc:creator>Ana Babi膰</dc:creator> <dc:creator>Ji艡铆 Eli谩拧ek</dc:creator> <dc:creator>Petr Jane膷ek</dc:creator> <dc:creator>Sergey Karpov</dc:creator> <dc:creator>Marta Kolarek</dc:creator> <dc:creator>Marina Manganaro</dc:creator> <dc:creator>Razmik Mirzoyan</dc:creator> <dc:identifier>doi: 10.3390/universe10090349</dc:identifier> <dc:source>Universe</dc:source> <dc:date>2024-08-30</dc:date> <prism:publicationName>Universe</prism:publicationName> <prism:publicationDate>2024-08-30</prism:publicationDate> <prism:volume>10</prism:volume> <prism:number>9</prism:number> <prism:section>Article</prism:section> <prism:startingPage>349</prism:startingPage> <prism:doi>10.3390/universe10090349</prism:doi> <prism:url>https://www.mdpi.com/2218-1997/10/9/349</prism:url> <cc:license rdf:resource="CC BY 4.0"/> </item> <item rdf:about="https://www.mdpi.com/2218-1997/10/9/348"> <title>Universe, Vol. 10, Pages 348: Infrared Regularization of Very Special Relativity Models</title> <link>https://www.mdpi.com/2218-1997/10/9/348</link> <description>We extend the Sim(2) invariant infrared regularization of Very Special Relativity models, that we have proposed recently, to include &amp;gamma;5 Dirac matrix. Then, we solve the Very Special Relativity Schwinger model, find the chiral anomaly, and clarify its meaning in the new context. In addition, we show that the triangle anomaly in four space-time dimensions agrees with the same object in standard quantum electrodynamics. Finally, we apply the infrared regularization to compute the large N limit of the Very Special Relativity Gross&amp;ndash;Neveu model.</description> <pubDate>2024-08-29</pubDate> <content:encoded><![CDATA[ Universe, Vol. 10, Pages 348: Infrared Regularization of Very Special Relativity Models Universe <a href="https://www.mdpi.com/2218-1997/10/9/348">doi: 10.3390/universe10090348</a> Authors: Jorge Alfaro We extend the Sim(2) invariant infrared regularization of Very Special Relativity models, that we have proposed recently, to include &amp;gamma;5 Dirac matrix. Then, we solve the Very Special Relativity Schwinger model, find the chiral anomaly, and clarify its meaning in the new context. In addition, we show that the triangle anomaly in four space-time dimensions agrees with the same object in standard quantum electrodynamics. Finally, we apply the infrared regularization to compute the large N limit of the Very Special Relativity Gross&amp;ndash;Neveu model. ]]></content:encoded> <dc:title>Infrared Regularization of Very Special Relativity Models</dc:title> <dc:creator>Jorge Alfaro</dc:creator> <dc:identifier>doi: 10.3390/universe10090348</dc:identifier> <dc:source>Universe</dc:source> <dc:date>2024-08-29</dc:date> <prism:publicationName>Universe</prism:publicationName> <prism:publicationDate>2024-08-29</prism:publicationDate> <prism:volume>10</prism:volume> <prism:number>9</prism:number> <prism:section>Article</prism:section> <prism:startingPage>348</prism:startingPage> <prism:doi>10.3390/universe10090348</prism:doi> <prism:url>https://www.mdpi.com/2218-1997/10/9/348</prism:url> <cc:license rdf:resource="CC BY 4.0"/> </item> <item rdf:about="https://www.mdpi.com/2218-1997/10/9/347"> <title>Universe, Vol. 10, Pages 347: Strange and Odd Morphology Extragalactic Radio Sources (STROMERSs): A Faint Images of the Radio Sky at Twenty-Centimeters (FIRST) Look at the Strange and Odd Radio Sources</title> <link>https://www.mdpi.com/2218-1997/10/9/347</link> <description>We report the identification of an extremely rare and peculiar set of irregular radio sources, termed &amp;ldquo;STROMERSs&amp;rdquo; (STRange and Odd Morphology Extragalactic Radio Sources).ingThe irregular radio sources with very anomalous morphologies that make them exceptionally different from all the known classes and subclasses of irregular radio sources are detected as STROMERSs. A thorough search for this class of sources from the Very Large Array (VLA) Faint Images of the Radio Sky at Twenty-Centimeters (FIRST) gave a total of nine such candidates. We checked the corresponding morphology of the identified sources in other frequency surveys. We found a detectable radio emission for all of the nine sources in the NRAO VLA Sky Survey (NVSS) at 1.4 GHz and in the TIFR GMRT Sky Survey (TGSS) at 150 MHz, while the same was found for only three sources in the Westerbork Northern Sky Survey (WENSS) at 625 MHz. However, the strange morphology was not found in all of those other survey images. We also characterized the sources with their corresponding physical parameters like optical counterpart, size, spectral index, and radio luminosity. ingThe estimated spectral values of the sources indicated that the STROMERSs were most likely radio galaxies. The presence of any nearby galaxy clusters for the STROMERSs was also checked.</description> <pubDate>2024-08-28</pubDate> <content:encoded><![CDATA[ Universe, Vol. 10, Pages 347: Strange and Odd Morphology Extragalactic Radio Sources (STROMERSs): A Faint Images of the Radio Sky at Twenty-Centimeters (FIRST) Look at the Strange and Odd Radio Sources Universe <a href="https://www.mdpi.com/2218-1997/10/9/347">doi: 10.3390/universe10090347</a> Authors: Soumen Kumar Bera Tapan K. Sasmal Soumen Mondal Taotao Fang Xuelei Chen We report the identification of an extremely rare and peculiar set of irregular radio sources, termed &amp;ldquo;STROMERSs&amp;rdquo; (STRange and Odd Morphology Extragalactic Radio Sources).ingThe irregular radio sources with very anomalous morphologies that make them exceptionally different from all the known classes and subclasses of irregular radio sources are detected as STROMERSs. A thorough search for this class of sources from the Very Large Array (VLA) Faint Images of the Radio Sky at Twenty-Centimeters (FIRST) gave a total of nine such candidates. We checked the corresponding morphology of the identified sources in other frequency surveys. We found a detectable radio emission for all of the nine sources in the NRAO VLA Sky Survey (NVSS) at 1.4 GHz and in the TIFR GMRT Sky Survey (TGSS) at 150 MHz, while the same was found for only three sources in the Westerbork Northern Sky Survey (WENSS) at 625 MHz. However, the strange morphology was not found in all of those other survey images. We also characterized the sources with their corresponding physical parameters like optical counterpart, size, spectral index, and radio luminosity. ingThe estimated spectral values of the sources indicated that the STROMERSs were most likely radio galaxies. The presence of any nearby galaxy clusters for the STROMERSs was also checked. ]]></content:encoded> <dc:title>Strange and Odd Morphology Extragalactic Radio Sources (STROMERSs): A Faint Images of the Radio Sky at Twenty-Centimeters (FIRST) Look at the Strange and Odd Radio Sources</dc:title> <dc:creator>Soumen Kumar Bera</dc:creator> <dc:creator>Tapan K. Sasmal</dc:creator> <dc:creator>Soumen Mondal</dc:creator> <dc:creator>Taotao Fang</dc:creator> <dc:creator>Xuelei Chen</dc:creator> <dc:identifier>doi: 10.3390/universe10090347</dc:identifier> <dc:source>Universe</dc:source> <dc:date>2024-08-28</dc:date> <prism:publicationName>Universe</prism:publicationName> <prism:publicationDate>2024-08-28</prism:publicationDate> <prism:volume>10</prism:volume> <prism:number>9</prism:number> <prism:section>Article</prism:section> <prism:startingPage>347</prism:startingPage> <prism:doi>10.3390/universe10090347</prism:doi> <prism:url>https://www.mdpi.com/2218-1997/10/9/347</prism:url> <cc:license rdf:resource="CC BY 4.0"/> </item> <item rdf:about="https://www.mdpi.com/2218-1997/10/9/346"> <title>Universe, Vol. 10, Pages 346: First Results of the CREDO-Maze Cosmic Ray Project</title> <link>https://www.mdpi.com/2218-1997/10/9/346</link> <description>The CREDO-Maze project is the concept for a network of stations recording local, extensive cosmic ray air showers. Each station consists of four small scintillation detectors and a control unit that monitors the cosmic ray flux 24 h a day and transmits the results to the central server. The modular design of each array allows the results to be used in educational classes on nuclear radiation, relativistic physics, and particle physics and as a teaching aid in regular school classrooms and more. As an example, we present here some preliminary results from the CREDO-Maze muon telescope missions to the Arctic and down into a deep salt mine, as well as the first shower-particle correlation measurements from a table-top experiment at Walailak University. These experiments show that the different geometric configurations of the CREDO-Maze detector set can be used for projects beyond the scope of the secondary school curriculum, and they can form the basis of student theses and dissertations at universities.</description> <pubDate>2024-08-28</pubDate> <content:encoded><![CDATA[ Universe, Vol. 10, Pages 346: First Results of the CREDO-Maze Cosmic Ray Project Universe <a href="https://www.mdpi.com/2218-1997/10/9/346">doi: 10.3390/universe10090346</a> Authors: Tadeusz Wibig Micha艂 Karbowiak Punsiri Dam-O Karol J醛drzejczak Jari Joutsenvaara Julia Puputti Juha Sorri Ari-Pekka Lepp盲nen The CREDO-Maze project is the concept for a network of stations recording local, extensive cosmic ray air showers. Each station consists of four small scintillation detectors and a control unit that monitors the cosmic ray flux 24 h a day and transmits the results to the central server. The modular design of each array allows the results to be used in educational classes on nuclear radiation, relativistic physics, and particle physics and as a teaching aid in regular school classrooms and more. As an example, we present here some preliminary results from the CREDO-Maze muon telescope missions to the Arctic and down into a deep salt mine, as well as the first shower-particle correlation measurements from a table-top experiment at Walailak University. These experiments show that the different geometric configurations of the CREDO-Maze detector set can be used for projects beyond the scope of the secondary school curriculum, and they can form the basis of student theses and dissertations at universities. ]]></content:encoded> <dc:title>First Results of the CREDO-Maze Cosmic Ray Project</dc:title> <dc:creator>Tadeusz Wibig</dc:creator> <dc:creator>Micha艂 Karbowiak</dc:creator> <dc:creator>Punsiri Dam-O</dc:creator> <dc:creator>Karol J醛drzejczak</dc:creator> <dc:creator>Jari Joutsenvaara</dc:creator> <dc:creator>Julia Puputti</dc:creator> <dc:creator>Juha Sorri</dc:creator> <dc:creator>Ari-Pekka Lepp盲nen</dc:creator> <dc:identifier>doi: 10.3390/universe10090346</dc:identifier> <dc:source>Universe</dc:source> <dc:date>2024-08-28</dc:date> <prism:publicationName>Universe</prism:publicationName> <prism:publicationDate>2024-08-28</prism:publicationDate> <prism:volume>10</prism:volume> <prism:number>9</prism:number> <prism:section>Article</prism:section> <prism:startingPage>346</prism:startingPage> <prism:doi>10.3390/universe10090346</prism:doi> <prism:url>https://www.mdpi.com/2218-1997/10/9/346</prism:url> <cc:license rdf:resource="CC BY 4.0"/> </item> <item rdf:about="https://www.mdpi.com/2218-1997/10/9/345"> <title>Universe, Vol. 10, Pages 345: On Quark&ndash;Lepton Mixing and the Leptonic CP Violation</title> <link>https://www.mdpi.com/2218-1997/10/9/345</link> <description>In the absence of a Grand Unified Theory framework, connecting the values of the mixing parameters in the quark-and-lepton sector is a difficult task, unless one introduces ad hoc relations among the matrices that diagonalize such different kinds of fermions. In this paper, we discuss in detail the possibility that the PMNS matrix is given by the product UPMNS=VCKM&amp;#9733;T&amp;#9733;, where T comes from the diagonalization of a see-saw like mass matrix that can be of a Bimaximal (BM), Tri-Bimaximal (TBM) and Golden Ratio (GR) form, and identify the leading corrections to such patterns that allow for a good fit to the leptonic mixing matrix as well as to the CP phase. We also show that the modified versions of BM, TBM and GR can easily accommodate the solar and atmospheric mass differences.</description> <pubDate>2024-08-28</pubDate> <content:encoded><![CDATA[ Universe, Vol. 10, Pages 345: On Quark&ndash;Lepton Mixing and the Leptonic CP Violation Universe <a href="https://www.mdpi.com/2218-1997/10/9/345">doi: 10.3390/universe10090345</a> Authors: Alessio Giarnetti Simone Marciano Davide Meloni In the absence of a Grand Unified Theory framework, connecting the values of the mixing parameters in the quark-and-lepton sector is a difficult task, unless one introduces ad hoc relations among the matrices that diagonalize such different kinds of fermions. In this paper, we discuss in detail the possibility that the PMNS matrix is given by the product UPMNS=VCKM&amp;#9733;T&amp;#9733;, where T comes from the diagonalization of a see-saw like mass matrix that can be of a Bimaximal (BM), Tri-Bimaximal (TBM) and Golden Ratio (GR) form, and identify the leading corrections to such patterns that allow for a good fit to the leptonic mixing matrix as well as to the CP phase. We also show that the modified versions of BM, TBM and GR can easily accommodate the solar and atmospheric mass differences. ]]></content:encoded> <dc:title>On Quark&amp;ndash;Lepton Mixing and the Leptonic CP Violation</dc:title> <dc:creator>Alessio Giarnetti</dc:creator> <dc:creator>Simone Marciano</dc:creator> <dc:creator>Davide Meloni</dc:creator> <dc:identifier>doi: 10.3390/universe10090345</dc:identifier> <dc:source>Universe</dc:source> <dc:date>2024-08-28</dc:date> <prism:publicationName>Universe</prism:publicationName> <prism:publicationDate>2024-08-28</prism:publicationDate> <prism:volume>10</prism:volume> <prism:number>9</prism:number> <prism:section>Article</prism:section> <prism:startingPage>345</prism:startingPage> <prism:doi>10.3390/universe10090345</prism:doi> <prism:url>https://www.mdpi.com/2218-1997/10/9/345</prism:url> <cc:license rdf:resource="CC BY 4.0"/> </item> <item rdf:about="https://www.mdpi.com/2218-1997/10/9/344"> <title>Universe, Vol. 10, Pages 344: Ionosonde Measurement Comparison during an Interplanetary Coronal Mass Ejection (ICME)- and a Corotating Interaction Region (CIR)-Driven Geomagnetic Storm over Europe</title> <link>https://www.mdpi.com/2218-1997/10/9/344</link> <description>A comparison of three types of ionosonde data from Europe during an interplanetary coronal mass ejection (ICME)- and a corotating interaction region (CIR)-driven geomagnetic storm event is detailed in this study. The selected events are 16&amp;ndash;20 March 2015 for the ICME-driven storm and 30 May to 4 June 2013 for the CIR-driven one. Ionospheric data from three European ionosonde stations, namely Pruhonice (PQ), Sopron (SO) and Rome (RO), are investigated. The ionospheric F2-layer responses to these geomagnetic events are analyzed with the ionospheric foF2 and h&amp;rsquo;F2 parameters, the calculated deltafoF2 and deltahF2 values, the ratio of total electron content (rTEC) and Thermosphere, Ionosphere, Mesosphere, Energetics and Dynamics (TIMED) satellite Global Ultraviolet Imager (GUVI) thermospheric [O]/[N2] measurement data. The storm-time and the quiet-day mean values are also compared, and it can be concluded that the quiet-day curves are similar at all the stations while the storm-time ones show the latitudinal dependence during the development of the storm. As a result of the electron density comparison, during the two events, it can be concluded that the sudden storm commencement (SSC) that characterized the ICME induced a traveling atmospheric disturbance (TAD) seen in the European stations in the main phase, while this is not seen in the CIR-driven ionospheric storm, which shows a stronger and more prolonged negative effect in all the stations, probably due to the season and the depleted O/N2 ratio.</description> <pubDate>2024-08-27</pubDate> <content:encoded><![CDATA[ Universe, Vol. 10, Pages 344: Ionosonde Measurement Comparison during an Interplanetary Coronal Mass Ejection (ICME)- and a Corotating Interaction Region (CIR)-Driven Geomagnetic Storm over Europe Universe <a href="https://www.mdpi.com/2218-1997/10/9/344">doi: 10.3390/universe10090344</a> Authors: Kitti Alexandra Ber茅nyi Loredana Perrone Dario Sabbagh Carlo Scotto Alessandro Ippolito 脕rp谩d Kis Veronika Barta A comparison of three types of ionosonde data from Europe during an interplanetary coronal mass ejection (ICME)- and a corotating interaction region (CIR)-driven geomagnetic storm event is detailed in this study. The selected events are 16&amp;ndash;20 March 2015 for the ICME-driven storm and 30 May to 4 June 2013 for the CIR-driven one. Ionospheric data from three European ionosonde stations, namely Pruhonice (PQ), Sopron (SO) and Rome (RO), are investigated. The ionospheric F2-layer responses to these geomagnetic events are analyzed with the ionospheric foF2 and h&amp;rsquo;F2 parameters, the calculated deltafoF2 and deltahF2 values, the ratio of total electron content (rTEC) and Thermosphere, Ionosphere, Mesosphere, Energetics and Dynamics (TIMED) satellite Global Ultraviolet Imager (GUVI) thermospheric [O]/[N2] measurement data. The storm-time and the quiet-day mean values are also compared, and it can be concluded that the quiet-day curves are similar at all the stations while the storm-time ones show the latitudinal dependence during the development of the storm. As a result of the electron density comparison, during the two events, it can be concluded that the sudden storm commencement (SSC) that characterized the ICME induced a traveling atmospheric disturbance (TAD) seen in the European stations in the main phase, while this is not seen in the CIR-driven ionospheric storm, which shows a stronger and more prolonged negative effect in all the stations, probably due to the season and the depleted O/N2 ratio. ]]></content:encoded> <dc:title>Ionosonde Measurement Comparison during an Interplanetary Coronal Mass Ejection (ICME)- and a Corotating Interaction Region (CIR)-Driven Geomagnetic Storm over Europe</dc:title> <dc:creator>Kitti Alexandra Ber茅nyi</dc:creator> <dc:creator>Loredana Perrone</dc:creator> <dc:creator>Dario Sabbagh</dc:creator> <dc:creator>Carlo Scotto</dc:creator> <dc:creator>Alessandro Ippolito</dc:creator> <dc:creator>脕rp谩d Kis</dc:creator> <dc:creator>Veronika Barta</dc:creator> <dc:identifier>doi: 10.3390/universe10090344</dc:identifier> <dc:source>Universe</dc:source> <dc:date>2024-08-27</dc:date> <prism:publicationName>Universe</prism:publicationName> <prism:publicationDate>2024-08-27</prism:publicationDate> <prism:volume>10</prism:volume> <prism:number>9</prism:number> <prism:section>Article</prism:section> <prism:startingPage>344</prism:startingPage> <prism:doi>10.3390/universe10090344</prism:doi> <prism:url>https://www.mdpi.com/2218-1997/10/9/344</prism:url> <cc:license rdf:resource="CC BY 4.0"/> </item> <item rdf:about="https://www.mdpi.com/2218-1997/10/9/343"> <title>Universe, Vol. 10, Pages 343: The Intrinsic Correlations between Prompt Emission and X-ray Flares of Gamma-Ray Bursts</title> <link>https://www.mdpi.com/2218-1997/10/9/343</link> <description>X-ray flare (XRF) is a common phenomenon in the X-ray afterglow of gamma-ray bursts (GRBs). Although it is commonly believed that XRFs may share a common origin with prompt emission, i.e., the &amp;ldquo;internal&amp;rdquo; origin, the origin of XRFs is still unknown. In this work, we compile a GRB sample containing 31 GRBs with a single XRF, a well-measured spectrum, and a redshift, and investigate the intrinsic properties and correlations between prompt emission and the XRFs of these events. We find that the distributions of main physical parameters of prompt emission and XRFs are basically log-normal. The median value of the rise time is shorter than the decay time for all flares, with a ratio of about 1:2, which is similar to the fast rise and exponential decay structure of prompt emission pulses. We also find that the prompt emission energy (Eiso) and peak luminosity (Liso) have tight correlations with XRF energy (EX,iso) and peak luminosity (LX,p), Eiso&amp;prop;EX,iso0.74 (LX,p0.62) and Liso&amp;prop;EX,iso0.85 (LX,p0.68). However, the durations of prompt emissions are independent of the temporal properties of XRFs. Furthermore, we also analyze the three-parameter correlations between prompt emissions and XRFs, and find that there are tight correlations among the XRF peak time (Tp,z), LX,p, and Eiso/Liso, LX,p&amp;prop;Tp,z&amp;minus;1.08Eiso0.84 and LX,p&amp;prop;Tp,z&amp;minus;1.09Liso0.71. Interestingly, these results are very similar to the properties of an X-ray plateau in GRBs, which indicates that X-ray flares and plateaus may have the same physical origin, and strongly supports that the two emission components originate from the late-time activity of the central engine.</description> <pubDate>2024-08-27</pubDate> <content:encoded><![CDATA[ Universe, Vol. 10, Pages 343: The Intrinsic Correlations between Prompt Emission and X-ray Flares of Gamma-Ray Bursts Universe <a href="https://www.mdpi.com/2218-1997/10/9/343">doi: 10.3390/universe10090343</a> Authors: Xing-Ting Zhong Si-Yuan Zhu Li-Ming Zhuo Zeng Zhang Fu-Wen Zhang X-ray flare (XRF) is a common phenomenon in the X-ray afterglow of gamma-ray bursts (GRBs). Although it is commonly believed that XRFs may share a common origin with prompt emission, i.e., the &amp;ldquo;internal&amp;rdquo; origin, the origin of XRFs is still unknown. In this work, we compile a GRB sample containing 31 GRBs with a single XRF, a well-measured spectrum, and a redshift, and investigate the intrinsic properties and correlations between prompt emission and the XRFs of these events. We find that the distributions of main physical parameters of prompt emission and XRFs are basically log-normal. The median value of the rise time is shorter than the decay time for all flares, with a ratio of about 1:2, which is similar to the fast rise and exponential decay structure of prompt emission pulses. We also find that the prompt emission energy (Eiso) and peak luminosity (Liso) have tight correlations with XRF energy (EX,iso) and peak luminosity (LX,p), Eiso&amp;prop;EX,iso0.74 (LX,p0.62) and Liso&amp;prop;EX,iso0.85 (LX,p0.68). However, the durations of prompt emissions are independent of the temporal properties of XRFs. Furthermore, we also analyze the three-parameter correlations between prompt emissions and XRFs, and find that there are tight correlations among the XRF peak time (Tp,z), LX,p, and Eiso/Liso, LX,p&amp;prop;Tp,z&amp;minus;1.08Eiso0.84 and LX,p&amp;prop;Tp,z&amp;minus;1.09Liso0.71. Interestingly, these results are very similar to the properties of an X-ray plateau in GRBs, which indicates that X-ray flares and plateaus may have the same physical origin, and strongly supports that the two emission components originate from the late-time activity of the central engine. ]]></content:encoded> <dc:title>The Intrinsic Correlations between Prompt Emission and X-ray Flares of Gamma-Ray Bursts</dc:title> <dc:creator>Xing-Ting Zhong</dc:creator> <dc:creator>Si-Yuan Zhu</dc:creator> <dc:creator>Li-Ming Zhuo</dc:creator> <dc:creator>Zeng Zhang</dc:creator> <dc:creator>Fu-Wen Zhang</dc:creator> <dc:identifier>doi: 10.3390/universe10090343</dc:identifier> <dc:source>Universe</dc:source> <dc:date>2024-08-27</dc:date> <prism:publicationName>Universe</prism:publicationName> <prism:publicationDate>2024-08-27</prism:publicationDate> <prism:volume>10</prism:volume> <prism:number>9</prism:number> <prism:section>Article</prism:section> <prism:startingPage>343</prism:startingPage> <prism:doi>10.3390/universe10090343</prism:doi> <prism:url>https://www.mdpi.com/2218-1997/10/9/343</prism:url> <cc:license rdf:resource="CC BY 4.0"/> </item> <item rdf:about="https://www.mdpi.com/2218-1997/10/9/342"> <title>Universe, Vol. 10, Pages 342: Stellar Modeling via the Tolman IV Solution: The Cases of the Massive Pulsar J0740+6620 and the HESS J1731-347 Compact Object</title> <link>https://www.mdpi.com/2218-1997/10/9/342</link> <description>We model compact objects of known stellar mass and radius made of isotropic matter within Einstein&amp;rsquo;s gravity. The interior solution describing hydrostatic equilibrium we are using throughout the manuscript corresponds to the Tolman IV exact analytic solution obtained a long time ago. The three free parameters of the solutions are determined by imposing the matching conditions for objects of known stellar mass and radius. Finally, using well established criteria, it is shown that, contrary to the Kohler Chao solution, the Tolman IV solution is compatible with all requirements for well-behaved and realistic solutions, except for the relativistic adiabatic index that diverges at the surface of stars. The divergence of the index &amp;Gamma; may be resolved, including a thin crust assuming a polytropic equation of state, which is precisely the case seen in studies of neutron stars. To the best of our knowledge, we model here for the first time the recently discovered massive pulsar PSR J0740+6620 and the strangely light HESS compact object via the Tolman IV solution. The present work may be of interest to model builders as well as a useful reference for future research.</description> <pubDate>2024-08-27</pubDate> <content:encoded><![CDATA[ Universe, Vol. 10, Pages 342: Stellar Modeling via the Tolman IV Solution: The Cases of the Massive Pulsar J0740+6620 and the HESS J1731-347 Compact Object Universe <a href="https://www.mdpi.com/2218-1997/10/9/342">doi: 10.3390/universe10090342</a> Authors: Grigoris Panotopoulos We model compact objects of known stellar mass and radius made of isotropic matter within Einstein&amp;rsquo;s gravity. The interior solution describing hydrostatic equilibrium we are using throughout the manuscript corresponds to the Tolman IV exact analytic solution obtained a long time ago. The three free parameters of the solutions are determined by imposing the matching conditions for objects of known stellar mass and radius. Finally, using well established criteria, it is shown that, contrary to the Kohler Chao solution, the Tolman IV solution is compatible with all requirements for well-behaved and realistic solutions, except for the relativistic adiabatic index that diverges at the surface of stars. The divergence of the index &amp;Gamma; may be resolved, including a thin crust assuming a polytropic equation of state, which is precisely the case seen in studies of neutron stars. To the best of our knowledge, we model here for the first time the recently discovered massive pulsar PSR J0740+6620 and the strangely light HESS compact object via the Tolman IV solution. The present work may be of interest to model builders as well as a useful reference for future research. ]]></content:encoded> <dc:title>Stellar Modeling via the Tolman IV Solution: The Cases of the Massive Pulsar J0740+6620 and the HESS J1731-347 Compact Object</dc:title> <dc:creator>Grigoris Panotopoulos</dc:creator> <dc:identifier>doi: 10.3390/universe10090342</dc:identifier> <dc:source>Universe</dc:source> <dc:date>2024-08-27</dc:date> <prism:publicationName>Universe</prism:publicationName> <prism:publicationDate>2024-08-27</prism:publicationDate> <prism:volume>10</prism:volume> <prism:number>9</prism:number> <prism:section>Communication</prism:section> <prism:startingPage>342</prism:startingPage> <prism:doi>10.3390/universe10090342</prism:doi> <prism:url>https://www.mdpi.com/2218-1997/10/9/342</prism:url> <cc:license rdf:resource="CC BY 4.0"/> </item> <item rdf:about="https://www.mdpi.com/2218-1997/10/9/341"> <title>Universe, Vol. 10, Pages 341: Modeling the TESS Light Curve of Ap Si Star MX TrA</title> <link>https://www.mdpi.com/2218-1997/10/9/341</link> <description>The TESS light curve of the silicon Ap star MX TrA was modeled using the observational surface distribution of silicon, iron, helium, and chromium obtained previously with the Doppler Imaging technique. The theoretical light curve was calculated using a grid of synthetic fluxes from line-by-line stellar atmosphere models with individual chemical abundances. The observational TESS light curve was fitted by a synthetic one with an accuracy better than 0.001 mag. The influence of Si and Fe abundance stratification on the amplitude of variability was estimated. Also, the wavelength dependence of the photometric amplitude and phase of the maximum light was modeled showing the typical Ap Si star behavior with increased amplitude and anti-phase variability in far ultraviolet caused by the flux redistribution.</description> <pubDate>2024-08-26</pubDate> <content:encoded><![CDATA[ Universe, Vol. 10, Pages 341: Modeling the TESS Light Curve of Ap Si Star MX TrA Universe <a href="https://www.mdpi.com/2218-1997/10/9/341">doi: 10.3390/universe10090341</a> Authors: Yury Pakhomov Ilya Potravnov Anna Romanovskaya Tatiana Ryabchikova The TESS light curve of the silicon Ap star MX TrA was modeled using the observational surface distribution of silicon, iron, helium, and chromium obtained previously with the Doppler Imaging technique. The theoretical light curve was calculated using a grid of synthetic fluxes from line-by-line stellar atmosphere models with individual chemical abundances. The observational TESS light curve was fitted by a synthetic one with an accuracy better than 0.001 mag. The influence of Si and Fe abundance stratification on the amplitude of variability was estimated. Also, the wavelength dependence of the photometric amplitude and phase of the maximum light was modeled showing the typical Ap Si star behavior with increased amplitude and anti-phase variability in far ultraviolet caused by the flux redistribution. ]]></content:encoded> <dc:title>Modeling the TESS Light Curve of Ap Si Star MX TrA</dc:title> <dc:creator>Yury Pakhomov</dc:creator> <dc:creator>Ilya Potravnov</dc:creator> <dc:creator>Anna Romanovskaya</dc:creator> <dc:creator>Tatiana Ryabchikova</dc:creator> <dc:identifier>doi: 10.3390/universe10090341</dc:identifier> <dc:source>Universe</dc:source> <dc:date>2024-08-26</dc:date> <prism:publicationName>Universe</prism:publicationName> <prism:publicationDate>2024-08-26</prism:publicationDate> <prism:volume>10</prism:volume> <prism:number>9</prism:number> <prism:section>Article</prism:section> <prism:startingPage>341</prism:startingPage> <prism:doi>10.3390/universe10090341</prism:doi> <prism:url>https://www.mdpi.com/2218-1997/10/9/341</prism:url> <cc:license rdf:resource="CC BY 4.0"/> </item> <item rdf:about="https://www.mdpi.com/2218-1997/10/9/340"> <title>Universe, Vol. 10, Pages 340: Source Count Distribution of Fermi LAT Gamma-Ray Blazars Using Novel Nonparametric Methods</title> <link>https://www.mdpi.com/2218-1997/10/9/340</link> <description>We utilized a sample from the Fermi-LAT 14-year Source Catalog by adjusting the flux detection threshold, enabling us to derive the intrinsic source count distribution dN/dF25 of extragalactic blazars using nonparametric, unbinned methods developed by Efron and Petrosian and Lynden-Bell. Subsequently, we evaluated the contribution of blazars to the extragalactic gamma-ray background. Our findings are summarized as follows: (1) There is no significant correlation between flux and spectral index values among blazars and their subclasses FSRQs and BL Lacs. (2) The intrinsic differential distributions of flux values exhibit a broken-power-law form, with parameters that closely match previous findings. The intrinsic photon index distributions are well described by a Gaussian form for FSRQs and BL Lacs individually, while a dual-Gaussian model provides a more appropriate fit for blazars as a whole. (3) Blazars contribute 34.5% to the extragalactic gamma-ray background and 16.8% to the extragalactic diffuse gamma-ray background. When examined separately, FSRQs and BL Lacs contribute 19.6% and 13% to the extragalactic gamma-ray background, respectively.</description> <pubDate>2024-08-26</pubDate> <content:encoded><![CDATA[ Universe, Vol. 10, Pages 340: Source Count Distribution of Fermi LAT Gamma-Ray Blazars Using Novel Nonparametric Methods Universe <a href="https://www.mdpi.com/2218-1997/10/9/340">doi: 10.3390/universe10090340</a> Authors: Xuhang Yin Houdun Zeng We utilized a sample from the Fermi-LAT 14-year Source Catalog by adjusting the flux detection threshold, enabling us to derive the intrinsic source count distribution dN/dF25 of extragalactic blazars using nonparametric, unbinned methods developed by Efron and Petrosian and Lynden-Bell. Subsequently, we evaluated the contribution of blazars to the extragalactic gamma-ray background. Our findings are summarized as follows: (1) There is no significant correlation between flux and spectral index values among blazars and their subclasses FSRQs and BL Lacs. (2) The intrinsic differential distributions of flux values exhibit a broken-power-law form, with parameters that closely match previous findings. The intrinsic photon index distributions are well described by a Gaussian form for FSRQs and BL Lacs individually, while a dual-Gaussian model provides a more appropriate fit for blazars as a whole. (3) Blazars contribute 34.5% to the extragalactic gamma-ray background and 16.8% to the extragalactic diffuse gamma-ray background. When examined separately, FSRQs and BL Lacs contribute 19.6% and 13% to the extragalactic gamma-ray background, respectively. ]]></content:encoded> <dc:title>Source Count Distribution of Fermi LAT Gamma-Ray Blazars Using Novel Nonparametric Methods</dc:title> <dc:creator>Xuhang Yin</dc:creator> <dc:creator>Houdun Zeng</dc:creator> <dc:identifier>doi: 10.3390/universe10090340</dc:identifier> <dc:source>Universe</dc:source> <dc:date>2024-08-26</dc:date> <prism:publicationName>Universe</prism:publicationName> <prism:publicationDate>2024-08-26</prism:publicationDate> <prism:volume>10</prism:volume> <prism:number>9</prism:number> <prism:section>Article</prism:section> <prism:startingPage>340</prism:startingPage> <prism:doi>10.3390/universe10090340</prism:doi> <prism:url>https://www.mdpi.com/2218-1997/10/9/340</prism:url> <cc:license rdf:resource="CC BY 4.0"/> </item> <item rdf:about="https://www.mdpi.com/2218-1997/10/9/339"> <title>Universe, Vol. 10, Pages 339: Energy-Momentum Squared Gravity: A Brief Overview</title> <link>https://www.mdpi.com/2218-1997/10/9/339</link> <description>In this work, we present a review of Energy-Momentum Squared Gravity (EMSG)&amp;mdash;more specifically, f(R,T&amp;mu;&amp;nu;T&amp;mu;&amp;nu;) gravity, where R represents the Ricci scalar and T&amp;mu;&amp;nu; denotes the energy-momentum tensor. The inclusion of quadratic contributions from the energy-momentum components has intriguing cosmological implications, particularly during the Universe&amp;rsquo;s early epochs. These effects dominate under high-energy conditions, enabling EMSG to potentially address unresolved issues in General Relativity (GR), such as the initial singularity and aspects of big-bang nucleosynthesis in certain models. The theory&amp;rsquo;s explicit non-minimal coupling between matter and geometry leads to the non-conservation of the energy-momentum tensor, which prompts the investigation of cosmological scenarios through the framework of irreversible thermodynamics of open systems. By employing this formalism, we interpret the energy-balance equations within EMSG from a thermodynamic perspective, viewing them as descriptions of irreversible matter creation processes. Since EMSG converges to GR in a vacuum and differences emerge only in the presence of an energy-momentum distribution, these distinctions become significant in high-curvature regions. Therefore, deviations from GR are expected to be pronounced in the dense cores of compact objects. This review delves into these facets of EMSG, highlighting its potential to shed light on some of the fundamental questions in modern cosmology and gravitational theory.</description> <pubDate>2024-08-23</pubDate> <content:encoded><![CDATA[ Universe, Vol. 10, Pages 339: Energy-Momentum Squared Gravity: A Brief Overview Universe <a href="https://www.mdpi.com/2218-1997/10/9/339">doi: 10.3390/universe10090339</a> Authors: Ricardo A. C. Cipriano Nailya Ganiyeva Tiberiu Harko Francisco S. N. Lobo Miguel A. S. Pinto Jo茫o Lu铆s Rosa In this work, we present a review of Energy-Momentum Squared Gravity (EMSG)&amp;mdash;more specifically, f(R,T&amp;mu;&amp;nu;T&amp;mu;&amp;nu;) gravity, where R represents the Ricci scalar and T&amp;mu;&amp;nu; denotes the energy-momentum tensor. The inclusion of quadratic contributions from the energy-momentum components has intriguing cosmological implications, particularly during the Universe&amp;rsquo;s early epochs. These effects dominate under high-energy conditions, enabling EMSG to potentially address unresolved issues in General Relativity (GR), such as the initial singularity and aspects of big-bang nucleosynthesis in certain models. The theory&amp;rsquo;s explicit non-minimal coupling between matter and geometry leads to the non-conservation of the energy-momentum tensor, which prompts the investigation of cosmological scenarios through the framework of irreversible thermodynamics of open systems. By employing this formalism, we interpret the energy-balance equations within EMSG from a thermodynamic perspective, viewing them as descriptions of irreversible matter creation processes. Since EMSG converges to GR in a vacuum and differences emerge only in the presence of an energy-momentum distribution, these distinctions become significant in high-curvature regions. Therefore, deviations from GR are expected to be pronounced in the dense cores of compact objects. This review delves into these facets of EMSG, highlighting its potential to shed light on some of the fundamental questions in modern cosmology and gravitational theory. ]]></content:encoded> <dc:title>Energy-Momentum Squared Gravity: A Brief Overview</dc:title> <dc:creator>Ricardo A. C. Cipriano</dc:creator> <dc:creator>Nailya Ganiyeva</dc:creator> <dc:creator>Tiberiu Harko</dc:creator> <dc:creator>Francisco S. N. Lobo</dc:creator> <dc:creator>Miguel A. S. Pinto</dc:creator> <dc:creator>Jo茫o Lu铆s Rosa</dc:creator> <dc:identifier>doi: 10.3390/universe10090339</dc:identifier> <dc:source>Universe</dc:source> <dc:date>2024-08-23</dc:date> <prism:publicationName>Universe</prism:publicationName> <prism:publicationDate>2024-08-23</prism:publicationDate> <prism:volume>10</prism:volume> <prism:number>9</prism:number> <prism:section>Review</prism:section> <prism:startingPage>339</prism:startingPage> <prism:doi>10.3390/universe10090339</prism:doi> <prism:url>https://www.mdpi.com/2218-1997/10/9/339</prism:url> <cc:license rdf:resource="CC BY 4.0"/> </item> <item rdf:about="https://www.mdpi.com/2218-1997/10/9/338"> <title>Universe, Vol. 10, Pages 338: Gravitational Particle Production and the Hubble Tension</title> <link>https://www.mdpi.com/2218-1997/10/9/338</link> <description>The effect of gravitational particle production of scalar particles on the total effective cosmic energy density (in the era after photon decoupling till the present) is considered. The effect is significant for heavy particles. It is found that gravitational particle production results in an effective increase in the directly measured value of the Hubble constant H0, while it does not affect the value of the Hubble constant in the calculation of the number density of baryons at the present time that is used to calculate recombination redshift. This may explain why the Hubble constants determined by local measurements and non-local measurements (such as CMB) are different. This suggests that gravitational particle production may have a non-negligible impact on H0 tension.</description> <pubDate>2024-08-23</pubDate> <content:encoded><![CDATA[ Universe, Vol. 10, Pages 338: Gravitational Particle Production and the Hubble Tension Universe <a href="https://www.mdpi.com/2218-1997/10/9/338">doi: 10.3390/universe10090338</a> Authors: Recai Erdem The effect of gravitational particle production of scalar particles on the total effective cosmic energy density (in the era after photon decoupling till the present) is considered. The effect is significant for heavy particles. It is found that gravitational particle production results in an effective increase in the directly measured value of the Hubble constant H0, while it does not affect the value of the Hubble constant in the calculation of the number density of baryons at the present time that is used to calculate recombination redshift. This may explain why the Hubble constants determined by local measurements and non-local measurements (such as CMB) are different. This suggests that gravitational particle production may have a non-negligible impact on H0 tension. ]]></content:encoded> <dc:title>Gravitational Particle Production and the Hubble Tension</dc:title> <dc:creator>Recai Erdem</dc:creator> <dc:identifier>doi: 10.3390/universe10090338</dc:identifier> <dc:source>Universe</dc:source> <dc:date>2024-08-23</dc:date> <prism:publicationName>Universe</prism:publicationName> <prism:publicationDate>2024-08-23</prism:publicationDate> <prism:volume>10</prism:volume> <prism:number>9</prism:number> <prism:section>Article</prism:section> <prism:startingPage>338</prism:startingPage> <prism:doi>10.3390/universe10090338</prism:doi> <prism:url>https://www.mdpi.com/2218-1997/10/9/338</prism:url> <cc:license rdf:resource="CC BY 4.0"/> </item> <item rdf:about="https://www.mdpi.com/2218-1997/10/9/337"> <title>Universe, Vol. 10, Pages 337: Minute-Cadence Observations of the LAMOST Fields with the TMTS: IV&mdash;Catalog of Cataclysmic Variables from the First 3-yr Survey</title> <link>https://www.mdpi.com/2218-1997/10/9/337</link> <description>The Tsinghua University&amp;ndash;Ma Huateng Telescopes for Survey (TMTS) started to monitor the LAMOST plates in 2020, leading to the discovery of numerous short-period eclipsing binaries, peculiar pulsators, flare stars, and other variable objects. Here, we present the uninterrupted light curves for a sample of 64 cataclysmic variables (CVs) observed/discovered using the TMTS during its first three-year observations, and we introduce new CVs and new light-variation periods (from known CVs) revealed through the TMTS observations. Thanks to the high-cadence observations of TMTS, diverse light variations, including superhumps, quasi-periodic oscillations, large-amplitude orbital modulations, and rotational modulations, are able to be detected in our CV samples, providing key observational clues for understanding the fast-developing physical processes in various CVs. All of these short-timescale light-curve features help further classify the subtypes of CV systems. We highlight the light-curve features observed in our CV sample and discuss further implications of minute-cadence light curves for CV identifications and classifications. Moreover, we examine the H&amp;alpha; emission lines in the spectra from our nonmagnetic CV samples (i.e., dwarf novae and nova-like subclasses) and find that the distribution of H&amp;alpha; emission strength shows significant differences between the sources with orbital periods above and below the period gap, which agrees with the trend seen from the SDSS nonmagnetic CV sample.</description> <pubDate>2024-08-23</pubDate> <content:encoded><![CDATA[ Universe, Vol. 10, Pages 337: Minute-Cadence Observations of the LAMOST Fields with the TMTS: IV&mdash;Catalog of Cataclysmic Variables from the First 3-yr Survey Universe <a href="https://www.mdpi.com/2218-1997/10/9/337">doi: 10.3390/universe10090337</a> Authors: Qichun Liu Jie Lin Xiaofeng Wang Zhibin Dai Yongkang Sun Gaobo Xi Jun Mo Jialian Liu Shengyu Yan Alexei V. Filippenko Thomas G. Brink Yi Yang Kishore C. Patra Yongzhi Cai Zhihao Chen Liyang Chen Fangzhou Guo Xiaojun Jiang Gaici Li Wenxiong Li Weili Lin Cheng Miao Xiaoran Ma Haowei Peng Qiqi Xia Danfeng Xiang Jicheng Zhang The Tsinghua University&amp;ndash;Ma Huateng Telescopes for Survey (TMTS) started to monitor the LAMOST plates in 2020, leading to the discovery of numerous short-period eclipsing binaries, peculiar pulsators, flare stars, and other variable objects. Here, we present the uninterrupted light curves for a sample of 64 cataclysmic variables (CVs) observed/discovered using the TMTS during its first three-year observations, and we introduce new CVs and new light-variation periods (from known CVs) revealed through the TMTS observations. Thanks to the high-cadence observations of TMTS, diverse light variations, including superhumps, quasi-periodic oscillations, large-amplitude orbital modulations, and rotational modulations, are able to be detected in our CV samples, providing key observational clues for understanding the fast-developing physical processes in various CVs. All of these short-timescale light-curve features help further classify the subtypes of CV systems. We highlight the light-curve features observed in our CV sample and discuss further implications of minute-cadence light curves for CV identifications and classifications. Moreover, we examine the H&amp;alpha; emission lines in the spectra from our nonmagnetic CV samples (i.e., dwarf novae and nova-like subclasses) and find that the distribution of H&amp;alpha; emission strength shows significant differences between the sources with orbital periods above and below the period gap, which agrees with the trend seen from the SDSS nonmagnetic CV sample. ]]></content:encoded> <dc:title>Minute-Cadence Observations of the LAMOST Fields with the TMTS: IV&amp;mdash;Catalog of Cataclysmic Variables from the First 3-yr Survey</dc:title> <dc:creator>Qichun Liu</dc:creator> <dc:creator>Jie Lin</dc:creator> <dc:creator>Xiaofeng Wang</dc:creator> <dc:creator>Zhibin Dai</dc:creator> <dc:creator>Yongkang Sun</dc:creator> <dc:creator>Gaobo Xi</dc:creator> <dc:creator>Jun Mo</dc:creator> <dc:creator>Jialian Liu</dc:creator> <dc:creator>Shengyu Yan</dc:creator> <dc:creator>Alexei V. Filippenko</dc:creator> <dc:creator>Thomas G. Brink</dc:creator> <dc:creator>Yi Yang</dc:creator> <dc:creator>Kishore C. Patra</dc:creator> <dc:creator>Yongzhi Cai</dc:creator> <dc:creator>Zhihao Chen</dc:creator> <dc:creator>Liyang Chen</dc:creator> <dc:creator>Fangzhou Guo</dc:creator> <dc:creator>Xiaojun Jiang</dc:creator> <dc:creator>Gaici Li</dc:creator> <dc:creator>Wenxiong Li</dc:creator> <dc:creator>Weili Lin</dc:creator> <dc:creator>Cheng Miao</dc:creator> <dc:creator>Xiaoran Ma</dc:creator> <dc:creator>Haowei Peng</dc:creator> <dc:creator>Qiqi Xia</dc:creator> <dc:creator>Danfeng Xiang</dc:creator> <dc:creator>Jicheng Zhang</dc:creator> <dc:identifier>doi: 10.3390/universe10090337</dc:identifier> <dc:source>Universe</dc:source> <dc:date>2024-08-23</dc:date> <prism:publicationName>Universe</prism:publicationName> <prism:publicationDate>2024-08-23</prism:publicationDate> <prism:volume>10</prism:volume> <prism:number>9</prism:number> <prism:section>Article</prism:section> <prism:startingPage>337</prism:startingPage> <prism:doi>10.3390/universe10090337</prism:doi> <prism:url>https://www.mdpi.com/2218-1997/10/9/337</prism:url> <cc:license rdf:resource="CC BY 4.0"/> </item> <cc:License rdf:about="https://creativecommons.org/licenses/by/4.0/"> <cc:permits rdf:resource="https://creativecommons.org/ns#Reproduction" /> <cc:permits rdf:resource="https://creativecommons.org/ns#Distribution" /> <cc:permits rdf:resource="https://creativecommons.org/ns#DerivativeWorks" /> </cc:License> </rdf:RDF>