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</div> <div class="control"> <button class="button is-small is-link">Go</button> </div> </div> </form> </div> </div> <nav class="pagination is-small is-centered breathe-horizontal" role="navigation" aria-label="pagination"> <a href="" class="pagination-previous is-invisible">Previous </a> <a href="/search/?searchtype=author&query=Lemos%2C+J+P+S&start=50" class="pagination-next" >Next </a> <ul class="pagination-list"> <li> <a href="/search/?searchtype=author&query=Lemos%2C+J+P+S&start=0" class="pagination-link is-current" aria-label="Goto page 1">1 </a> </li> <li> <a href="/search/?searchtype=author&query=Lemos%2C+J+P+S&start=50" class="pagination-link " aria-label="Page 2" aria-current="page">2 </a> </li> <li> <a href="/search/?searchtype=author&query=Lemos%2C+J+P+S&start=100" class="pagination-link " aria-label="Page 3" aria-current="page">3 </a> </li> <li> <a href="/search/?searchtype=author&query=Lemos%2C+J+P+S&start=150" class="pagination-link " aria-label="Page 4" aria-current="page">4 </a> </li> </ul> </nav> <ol class="breathe-horizontal" start="1"> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2411.14528">arXiv:2411.14528</a> <span> [<a href="https://arxiv.org/pdf/2411.14528">pdf</a>, <a href="https://arxiv.org/format/2411.14528">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="General Relativity and Quantum Cosmology">gr-qc</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="High Energy Physics - Theory">hep-th</span> </div> </div> <p class="title is-5 mathjax"> Penrose and super-Penrose energy extraction from a Reissner-Nordstr枚m black hole spacetime with a cosmological constant through the BSW mechanism: Full story </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/gr-qc?searchtype=author&query=Feiteira%2C+D">Duarte Feiteira</a>, <a href="/search/gr-qc?searchtype=author&query=Lemos%2C+J+P+S">Jos茅 P. S. Lemos</a>, <a href="/search/gr-qc?searchtype=author&query=Zaslavskii%2C+O+B">Oleg B. Zaslavskii</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2411.14528v1-abstract-short" style="display: inline;"> The Penrose process, a process that transfers energy from a black hole to infinity, together with the BSW mechanism, which uses collisions of ingoing particles at the event horizon of a black hole to locally produce large amounts of energy, is studied in a combined description for a $d$ dimensional extremal Reissner-Nordstr枚m black hole spacetime with negative, zero, or positive cosmological const… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2411.14528v1-abstract-full').style.display = 'inline'; document.getElementById('2411.14528v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2411.14528v1-abstract-full" style="display: none;"> The Penrose process, a process that transfers energy from a black hole to infinity, together with the BSW mechanism, which uses collisions of ingoing particles at the event horizon of a black hole to locally produce large amounts of energy, is studied in a combined description for a $d$ dimensional extremal Reissner-Nordstr枚m black hole spacetime with negative, zero, or positive cosmological constant, i.e., for an asymptotically anti-de Sitter (AdS), flat, or de Sitter (dS) spacetime. In an extremal Reissner-Nordstr枚m black hole background, in the vicinity of the horizon, several types of radial collisions between electrically charged particles can be considered. The most interesting one is between a critical particle, with its electric charge adjusted in a specific way, and a usual particle, as it gives a divergent center of mass frame energy locally, this being a favorable but not sufficient condition to extract energy from the black hole. To understand whether energy can be extracted in such a collisional Penrose process, we investigate in detail a collision between ingoing particles 1 and 2, from which particles 3 and 4 emerge, with the possibility that particle 3 can carry energy far out from the black hole horizon. One finds that the mass, energy, electric charge, and initial direction of motion of particle 3 can have different values, depending on the collision internal process, but these values lie within some range. Moreover, the energy of particle 3 can be arbitrarily high but not infinite, characterizing a super-Penrose process. It is also shown that particle 4 has negative energy, living in its own electric ergosphere before being engulfed by the event horizon. For zero cosmological constant the results do not depend on the number of dimensions, but they do for nonzero cosmological constant, which also introduces differences in the lower bound for the energy extracted. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2411.14528v1-abstract-full').style.display = 'none'; document.getElementById('2411.14528v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 21 November, 2024; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> November 2024. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">20 pages, 1 figure</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2410.12902">arXiv:2410.12902</a> <span> [<a href="https://arxiv.org/pdf/2410.12902">pdf</a>, <a href="https://arxiv.org/format/2410.12902">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Physics - Theory">hep-th</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Statistical Mechanics">cond-mat.stat-mech</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="General Relativity and Quantum Cosmology">gr-qc</span> </div> </div> <p class="title is-5 mathjax"> Gibbons-Hawking action for electrically charged black holes in the canonical ensemble and Davies' thermodynamic theory of black holes </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/gr-qc?searchtype=author&query=Fernandes%2C+T+V">Tiago V. Fernandes</a>, <a href="/search/gr-qc?searchtype=author&query=Lemos%2C+J+P+S">Jos茅 P. S. Lemos</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2410.12902v1-abstract-short" style="display: inline;"> We establish the connection between the Gibbons-Hawking Euclidean path integral approach applied to the canonical ensemble of a Reissner-Nordstr枚m black hole and the thermodynamic theory of black holes of Davies. We build the ensemble, characterized by a reservoir at infinity at temperature $T$ and electric charge $Q$, in $d$ dimensions. The Euclidean path integral yields the action and partition… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2410.12902v1-abstract-full').style.display = 'inline'; document.getElementById('2410.12902v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2410.12902v1-abstract-full" style="display: none;"> We establish the connection between the Gibbons-Hawking Euclidean path integral approach applied to the canonical ensemble of a Reissner-Nordstr枚m black hole and the thermodynamic theory of black holes of Davies. We build the ensemble, characterized by a reservoir at infinity at temperature $T$ and electric charge $Q$, in $d$ dimensions. The Euclidean path integral yields the action and partition function. In zero loop, we uncover two solutions, one with horizon radius $r_{+1}$ the least massive, the other with $r_{+2}$. We find a saddle point separating the solutions at $T_s$ and $Q_s$ with radius $r_{+s}$. For $T > T_s$ there is only hot flat space with charge at infinity. We derive the thermodynamics. The heat capacity gives that $T_s$ and $Q_s$ separate stable, $r_{+1}$, from unstable, $r_{+2}$ , solutions, the phase transition being second order. The free energy of the stable solution is positive, so if the system is a black hole it makes a first order transition to hot space. An interpretation of the results as energy wavelengths is attempted. For $d = 4$, the thermodynamics from the path integral applied to the canonical ensemble is precisely the Davies thermodynamics theory of black holes, with $T_s$ being the Davies point. We sketch the case $d = 5$. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2410.12902v1-abstract-full').style.display = 'none'; document.getElementById('2410.12902v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 16 October, 2024; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> October 2024. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">15 pages, 2 figures</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2402.05166">arXiv:2402.05166</a> <span> [<a href="https://arxiv.org/pdf/2402.05166">pdf</a>, <a href="https://arxiv.org/format/2402.05166">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Physics - Theory">hep-th</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Statistical Mechanics">cond-mat.stat-mech</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="General Relativity and Quantum Cosmology">gr-qc</span> </div> </div> <p class="title is-5 mathjax"> Hot spaces with positive cosmological constant in the canonical ensemble: de Sitter solution, Schwarzschild-de Sitter black hole, and Nariai universe </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/gr-qc?searchtype=author&query=Lemos%2C+J+P+S">Jos茅 P. S. Lemos</a>, <a href="/search/gr-qc?searchtype=author&query=Zaslavskii%2C+O+B">Oleg B. Zaslavskii</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2402.05166v1-abstract-short" style="display: inline;"> In a space with positive cosmological constant $螞$, we consider a black hole surrounded by a heat reservoir at radius $R$ and temperature $T$, i.e., we analyze the Schwarzschild-de Sitter black hole in a cavity. We use the Euclidean path integral approach to quantum gravity to study its canonical ensemble and thermodynamics. We give the action, energy, entropy, temperature, and heat capacity. $T$,… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2402.05166v1-abstract-full').style.display = 'inline'; document.getElementById('2402.05166v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2402.05166v1-abstract-full" style="display: none;"> In a space with positive cosmological constant $螞$, we consider a black hole surrounded by a heat reservoir at radius $R$ and temperature $T$, i.e., we analyze the Schwarzschild-de Sitter black hole in a cavity. We use the Euclidean path integral approach to quantum gravity to study its canonical ensemble and thermodynamics. We give the action, energy, entropy, temperature, and heat capacity. $T$, $螞$, the black hole radius $r_+$, and the cosmological horizon radius $r_{\rm c}$, are gauged in $R$ units to $RT$, $螞R^2$, $\frac{r_+}{R}$, and $\frac{r_{\rm c}}{R}$. The whole extension of $螞R^2$, $0\leq螞R^2\leq 3$, is divided into three ranges. The first, $0\leq螞R^2<1$, includes York's Schwarzschild black holes. The second range, $螞R^2=1$, opens up a folder of Nariai universes. The third range, $1<螞R^2\leq 3$, is unusual. One feature here is that it interchanges the cosmological horizon with the black hole horizon. The end point, $螞R^2=3$, only existing for infinite $RT$, is a cavity filled with de Sitter space, except for a singularity, with the cosmological horizon coinciding with the reservoir. For the three ranges, for low temperatures, there are no black holes and no Nariai universes, the space is hot de Sitter. The value of $RT$ that divides the nonexistence from existence of black holes or Nariai universes, depends on $螞R^2$. For each $螞R^2\neq1$, for high temperatures, there is one small and thermodynamically unstable black hole, and one large and stable. For $螞R^2=1$, for high temperatures, there is the unstable black hole, and the neutrally stable Nariai universe. Phase transitions can be analyzed. The transitions are between the black hole and hot de Sitter and between Nariai and hot de Sitter. The Buchdahl radius, the radius for collapse, plays an interesting role in the analysis. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2402.05166v1-abstract-full').style.display = 'none'; document.getElementById('2402.05166v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 7 February, 2024; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> February 2024. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">34 pages, 8 figures</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Physical Review D 109, 084016 (2024) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2401.13039">arXiv:2401.13039</a> <span> [<a href="https://arxiv.org/pdf/2401.13039">pdf</a>, <a href="https://arxiv.org/format/2401.13039">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="General Relativity and Quantum Cosmology">gr-qc</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="High Energy Physics - Theory">hep-th</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1103/PhysRevD.109.064065">10.1103/PhysRevD.109.064065 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Penrose process in Reissner-Nordstr枚m-AdS black hole spacetimes: Black hole energy factories and black hole bombs </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/gr-qc?searchtype=author&query=Feiteira%2C+D">Duarte Feiteira</a>, <a href="/search/gr-qc?searchtype=author&query=Lemos%2C+J+P+S">Jos茅 P. S. Lemos</a>, <a href="/search/gr-qc?searchtype=author&query=Zaslavskii%2C+O+B">Oleg B. Zaslavskii</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2401.13039v1-abstract-short" style="display: inline;"> The Penrose process for the decay of electrically charged particles in a Reissner-Nordstr枚m-anti-de Sitter black hole spacetime is studied. To extract large quantities of energy one needs to mount a recursive Penrose process where particles are confined and can bounce back to suffer ever again a decaying process in the black hole electric ergoregion. In an asymptotically anti-de Sitter (AdS) space… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2401.13039v1-abstract-full').style.display = 'inline'; document.getElementById('2401.13039v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2401.13039v1-abstract-full" style="display: none;"> The Penrose process for the decay of electrically charged particles in a Reissner-Nordstr枚m-anti-de Sitter black hole spacetime is studied. To extract large quantities of energy one needs to mount a recursive Penrose process where particles are confined and can bounce back to suffer ever again a decaying process in the black hole electric ergoregion. In an asymptotically anti-de Sitter (AdS) spacetime, two situations of confinement are possible. One situation uses a reflecting mirror at some radius, which obliges the energetic outgoing particles to return to the decaying point. The other situation uses the natural AdS property that sends back at some intrinsic returning radius those outgoing energetic particles. In addition, besides the conservation laws the decaying process must obey, one has to set conditions at the decaying point for the particles debris. These conditions restrain the possible scenarios, but there are still a great number of available scenarios for the decays. Within these, we choose two scenarios, scenario 1 and scenario 2, that pertain to the masses and electric charges of the final particles. Thus, in the mirror situation we find that scenario 1 leads to a black hole energy factory, and scenario 2 ends in a black hole bomb. In the no mirror situation, i.e., pure Reissner-Nordstr枚m-AdS, scenario 1 leads again to a black hole energy factory, but scenario 2 yields no bomb. This happens because the volume in which the particles are confined increases to infinity along the chain of decays, leading to a zero value of the extracted energy per unit volume and the bomb is demined. The whole treatment performed here involves no backreaction on the black hole mass and electric charge, nevertheless we speculate that the end state of the recursive process is a Reissner-Nordstr枚m-AdS black hole with very short hair, i.e., with one particle at rest at some definite radius. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2401.13039v1-abstract-full').style.display = 'none'; document.getElementById('2401.13039v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 23 January, 2024; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> January 2024. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">20 pages, 1 figure</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Phys. Rev. D 109, 064065 (2024) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2401.13030">arXiv:2401.13030</a> <span> [<a href="https://arxiv.org/pdf/2401.13030">pdf</a>, <a href="https://arxiv.org/format/2401.13030">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="General Relativity and Quantum Cosmology">gr-qc</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="High Energy Physics - Theory">hep-th</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Mathematical Physics">math-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1103/PhysRevD.109.064041">10.1103/PhysRevD.109.064041 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Normal modes of Proca fields in AdS$_d$ spacetime </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/gr-qc?searchtype=author&query=Lopes%2C+D">David Lopes</a>, <a href="/search/gr-qc?searchtype=author&query=Fernandes%2C+T+V">Tiago V. Fernandes</a>, <a href="/search/gr-qc?searchtype=author&query=Lemos%2C+J+P+S">Jos茅 P. S. Lemos</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2401.13030v2-abstract-short" style="display: inline;"> The normal modes of Proca field perturbations in $d$-dimensional anti-de Sitter spacetime, AdS$_d$ for short, with reflective Dirichlet boundary conditions, are obtained exactly. Within the Ishibashi-Kodama framework, we decompose the Proca field in scalar-type and vector-type components, according to their tensorial behavior on the $(d-2)$-sphere $\mathcal{S}^{d-2}$. Two of the degrees of freedom… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2401.13030v2-abstract-full').style.display = 'inline'; document.getElementById('2401.13030v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2401.13030v2-abstract-full" style="display: none;"> The normal modes of Proca field perturbations in $d$-dimensional anti-de Sitter spacetime, AdS$_d$ for short, with reflective Dirichlet boundary conditions, are obtained exactly. Within the Ishibashi-Kodama framework, we decompose the Proca field in scalar-type and vector-type components, according to their tensorial behavior on the $(d-2)$-sphere $\mathcal{S}^{d-2}$. Two of the degrees of freedom of the Proca field are described by scalar-type components, which in general are coupled due to the mass of the field, but in AdS$_d$ we show that they can be decoupled. The other $d-3$ degrees of freedom of the field are described by a vector-type component that generically decouples completely. The normal modes and their frequencies for both the scalar-type and vector-type components of the Proca field are then obtained analytically. Additionally, we analyze the normal modes of the Maxwell field as the massless limit of the Proca field. We find that for scalar-type perturbations in $d=4$ there is a discontinuity in the massless limit, in $d=5$ the massless limit is well defined using Dirichlet-Neumann rather than Dirichlet boundary conditions, and in $d>5$ the massless limit is completely well defined, i.e., it is obtained smoothly from the massless limit of the scalar-type perturbations of the Proca field. For vector-type perturbations the Maxwell field limit is obtained smoothly for all $d$ from the massless limit of the vector-type perturbations of the Proca field. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2401.13030v2-abstract-full').style.display = 'none'; document.getElementById('2401.13030v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 15 March, 2024; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 23 January, 2024; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> January 2024. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">16 pages</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Phys. Rev. D 109, 064041 (2024) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2309.12388">arXiv:2309.12388</a> <span> [<a href="https://arxiv.org/pdf/2309.12388">pdf</a>, <a href="https://arxiv.org/format/2309.12388">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Physics - Theory">hep-th</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Statistical Mechanics">cond-mat.stat-mech</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="General Relativity and Quantum Cosmology">gr-qc</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1103/PhysRevD.108.084053">10.1103/PhysRevD.108.084053 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Grand canonical ensemble of a $d$-dimensional Reissner-Nordstr枚m black hole in a cavity </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/gr-qc?searchtype=author&query=Fernandes%2C+T+V">Tiago V. Fernandes</a>, <a href="/search/gr-qc?searchtype=author&query=Lemos%2C+J+P+S">Jos茅 P. S. Lemos</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2309.12388v2-abstract-short" style="display: inline;"> The grand canonical ensemble of a $d$-dimensional Reissner-Nordstr枚m black hole space in a cavity is analyzed. The realization of this ensemble is made through the Euclidean path integral approach by giving the Euclidean action for the black hole with the correct topology, and boundary conditions corresponding to a cavity, where the fixed quantities are the temperature and the electric potential.… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2309.12388v2-abstract-full').style.display = 'inline'; document.getElementById('2309.12388v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2309.12388v2-abstract-full" style="display: none;"> The grand canonical ensemble of a $d$-dimensional Reissner-Nordstr枚m black hole space in a cavity is analyzed. The realization of this ensemble is made through the Euclidean path integral approach by giving the Euclidean action for the black hole with the correct topology, and boundary conditions corresponding to a cavity, where the fixed quantities are the temperature and the electric potential. One performs a zero loop approximation to find and analyze the stationary points of the reduced action. This yields two solutions for the electrically charged black hole, $r_{+1}$, which is the smaller and unstable, and $r_{+2}$, which is the larger and stable. One also analyzes the most probable configurations, which are either a stable charged black hole or hot flat space, mimicked by a nongravitating charged shell. Making the correspondence between the action and the grand potential, one can get the black hole thermodynamic quantities, such as the entropy, the mean charge, the mean energy, and the thermodynamic pressure, as well as the Smarr formula, shown to be valid only for the unstable black hole. We find that thermodynamic stability is related to the positivity of the heat capacity at constant electric potential and area of the cavity. We also comment on the most favorable thermodynamic phases and phase transitions. We then choose $d = 5$, which is singled out naturally from the other higher dimensions as it provides an exact solution for the problem, and apply all the results previously found. The case $d = 4$ is mentioned. We compare thermodynamic radii with the photonic orbit radius and the Buchdahl-Andr茅asson-Wright bound radius in $d$-dimensional Reissner-Nordstr枚m spacetimes and find they are unconnected, showing that the connections displayed in the Schwarzschild case are not generic, rather they are very restricted holding only in the pure gravitational situation. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2309.12388v2-abstract-full').style.display = 'none'; document.getElementById('2309.12388v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 26 October, 2023; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 21 September, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> September 2023. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">28 pages, 5 figures</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Phys. Rev. D 108, 084053 (2023) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2305.06829">arXiv:2305.06829</a> <span> [<a href="https://arxiv.org/pdf/2305.06829">pdf</a>, <a href="https://arxiv.org/format/2305.06829">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="General Relativity and Quantum Cosmology">gr-qc</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="High Energy Physics - Theory">hep-th</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1007/s10714-023-03107-6">10.1007/s10714-023-03107-6 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Traversable wormholes with double layer thin shells in quadratic gravity </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/gr-qc?searchtype=author&query=Rosa%2C+J+L">Joao Lu铆s Rosa</a>, <a href="/search/gr-qc?searchtype=author&query=Andr%C3%A9%2C+R">Rui Andr茅</a>, <a href="/search/gr-qc?searchtype=author&query=Lemos%2C+J+P+S">Jos茅 P. S. Lemos</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2305.06829v1-abstract-short" style="display: inline;"> In quadratic gravity, the junction conditions are six and permit the appearance of double layer thin shells. Double layers arise typically in theories with dipoles, i.e., two opposite charges, such as electromagnetic theories, and appear exceptionally in gravitational theories, which are theories with a single charge. We explore this property of the existence of double layers in quadratic gravity… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2305.06829v1-abstract-full').style.display = 'inline'; document.getElementById('2305.06829v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2305.06829v1-abstract-full" style="display: none;"> In quadratic gravity, the junction conditions are six and permit the appearance of double layer thin shells. Double layers arise typically in theories with dipoles, i.e., two opposite charges, such as electromagnetic theories, and appear exceptionally in gravitational theories, which are theories with a single charge. We explore this property of the existence of double layers in quadratic gravity to find and study traversable wormholes in which the two domains of the wormhole interior region, where the throat is located, are matched to two vacuum domains of the exterior region via the use of two double layer thin shells. The quadratic gravity we use is essentially given by a $R+伪R^2$ Lagrangian, where $R$ is the Ricci scalar of the spacetime and $伪$ is a coupling constant, plus a matter Lagrangian. The null energy condition, or NEC for short, is tested for the whole wormhole spacetime. The analysis shows that the NEC is satisfied for the stress-energy tensor of the matter in the whole wormhole interior region, notably at the throat, and is satisfied for some of the stress-energy tensor components of the matter at the double layer thin shell, but is not satisfied for some other components, namely, the double layer stress-energy distribution component, at the thin shell. This seems to mean that the NEC is basically impossible, or at least very hard, to be satisfied when double layer thin shells are present. Single layer thin shells are also admitted within the theory, and we present thin shell traversable wormholes, i.e., wormholes without interior, with a single layer thin shell at the throat for which the corresponding stress-energy tensor satisfies the NEC, that are asymmetric, i.e., with two different vacuum domains of the exterior region joined at the wormhole throat. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2305.06829v1-abstract-full').style.display = 'none'; document.getElementById('2305.06829v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 11 May, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> May 2023. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">22 pages, 3 figures</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Gen. Relativ. Gravit. 55, 65 (2023) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2304.06740">arXiv:2304.06740</a> <span> [<a href="https://arxiv.org/pdf/2304.06740">pdf</a>, <a href="https://arxiv.org/ps/2304.06740">ps</a>, <a href="https://arxiv.org/format/2304.06740">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Physics - Theory">hep-th</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="General Relativity and Quantum Cosmology">gr-qc</span> </div> </div> <p class="title is-5 mathjax"> Black holes and hot shells in the Euclidean path integral approach to quantum gravity </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/gr-qc?searchtype=author&query=Lemos%2C+J+P+S">Jos茅 P. S. Lemos</a>, <a href="/search/gr-qc?searchtype=author&query=Zaslavskii%2C+O+B">O. B. Zaslavskii</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2304.06740v1-abstract-short" style="display: inline;"> We study a spherical black hole surrounded by a hot self-gravitating thin shell in the canonical ensemble, i.e., a black hole and a hot shell inside a heat reservoir acting as a boundary with its area and temperature fixed. To work out the quantum partition function, from which the thermodynamics of the system follows, we use the Euclidean path integral approach to quantum gravity that identifies… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2304.06740v1-abstract-full').style.display = 'inline'; document.getElementById('2304.06740v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2304.06740v1-abstract-full" style="display: none;"> We study a spherical black hole surrounded by a hot self-gravitating thin shell in the canonical ensemble, i.e., a black hole and a hot shell inside a heat reservoir acting as a boundary with its area and temperature fixed. To work out the quantum partition function, from which the thermodynamics of the system follows, we use the Euclidean path integral approach to quantum gravity that identifies the path integral of the gravitational system with the partition function. In a semiclassical approximation, one needs only to compute the classical action of the system. Then, one finds that the total entropy, i.e., the sum of black hole and matter entropies, is a function of the gravitational radius of the system alone. So, the black hole inside the shell has no direct influence on the entropy. One also finds the free energy, the thermodynamic energy, and the temperature stratification. The reservoir temperature is composed of a free function of the gravitational radius of the system divided by the redshift. Upon specification of the reduced temperature free function, the solutions for the gravitational radii compatible with the data are found. The black hole inside has two possible horizon radii. It is shown that there is a first law of thermodynamics for the system, another for the hot shell, and yet another for the black hole. A thermodynamic stability analysis is performed. By specifying for the free function the Hawking temperature for the gravitational radius of the system, which is not a black hole, one finds a remarkable exact thermodynamic solution. With it one establishes that pure black holes, hot shells with a black hole, pure hot shells, and hot flat spaces are phases that cohabit in the ensemble, with some acting as thermodynamic mimickers. This exact solution is a model to situations involving black holes and hot gravitons. The high temperature limits reveal important aspects. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2304.06740v1-abstract-full').style.display = 'none'; document.getElementById('2304.06740v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 13 April, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> April 2023. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">26 pages, 2 figures</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Classical Quantum Gravity 40, 235012 (2023) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2303.03104">arXiv:2303.03104</a> <span> [<a href="https://arxiv.org/pdf/2303.03104">pdf</a>, <a href="https://arxiv.org/ps/2303.03104">ps</a>, <a href="https://arxiv.org/format/2303.03104">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="General Relativity and Quantum Cosmology">gr-qc</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Cosmology and Nongalactic Astrophysics">astro-ph.CO</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="High Energy Physics - Theory">hep-th</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1103/PhysRevD.107.084004">10.1103/PhysRevD.107.084004 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Relativistic cosmology and intrinsic spin of matter: Results and theorems in Einstein-Cartan theory </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/gr-qc?searchtype=author&query=Luz%2C+P">Paulo Luz</a>, <a href="/search/gr-qc?searchtype=author&query=Lemos%2C+J+P+S">Jos茅 P. S. Lemos</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2303.03104v1-abstract-short" style="display: inline;"> We start by presenting the general set of structure equations for the 1+3 threading spacetime decomposition in 4 spacetime dimensions, valid for any theory of gravitation based on a metric compatible affine connection. We then apply these equations to the study of cosmological solutions of the Einstein-Cartan theory in which the matter is modeled by a perfect fluid with intrinsic spin. It is shown… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2303.03104v1-abstract-full').style.display = 'inline'; document.getElementById('2303.03104v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2303.03104v1-abstract-full" style="display: none;"> We start by presenting the general set of structure equations for the 1+3 threading spacetime decomposition in 4 spacetime dimensions, valid for any theory of gravitation based on a metric compatible affine connection. We then apply these equations to the study of cosmological solutions of the Einstein-Cartan theory in which the matter is modeled by a perfect fluid with intrinsic spin. It is shown that the metric tensor can be described by a generic FLRW solution. However, due to the presence of torsion the Weyl tensors might not vanish. The coupling between the torsion and Weyl tensors leads to the conclusion that, in this cosmological model, the universe must either be flat or open, excluding definitely the possibility of a closed universe. In the open case, we derive a wave equation for the traceless part of the magnetic part of the Weyl tensor and show how the intrinsic spin of matter in a dynamic universe leads to the generation and emission of gravitational waves. Lastly, in this cosmological model, it is found that the torsion tensor, which has an intrinsic spin as its source, contributes to a positive accelerated expansion of the universe. Comparing the theoretical predictions of the model with the current experimental data, we conclude that torsion cannot completely replace the role of a cosmological constant. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2303.03104v1-abstract-full').style.display = 'none'; document.getElementById('2303.03104v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 2 March, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> March 2023. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">43 pages</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Physical Review D 107, 084004 (2023) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2301.10248">arXiv:2301.10248</a> <span> [<a href="https://arxiv.org/pdf/2301.10248">pdf</a>, <a href="https://arxiv.org/ps/2301.10248">ps</a>, <a href="https://arxiv.org/format/2301.10248">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="General Relativity and Quantum Cosmology">gr-qc</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="High Energy Physics - Theory">hep-th</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1007/s10714-022-03052-w">10.1007/s10714-022-03052-w <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Normal modes of Proca fields in AdS spacetime </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/gr-qc?searchtype=author&query=Fernandes%2C+T+V">Tiago V. Fernandes</a>, <a href="/search/gr-qc?searchtype=author&query=Hilditch%2C+D">David Hilditch</a>, <a href="/search/gr-qc?searchtype=author&query=Lemos%2C+J+P+S">Jos茅 P. S. Lemos</a>, <a href="/search/gr-qc?searchtype=author&query=Cardoso%2C+V">V铆tor Cardoso</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2301.10248v1-abstract-short" style="display: inline;"> A normal mode analysis for Proca fields in the anti-de Sitter (AdS) spacetime is given. It is found that the equations for the Proca field can be decoupled analytically. This is performed by changing the basis of the vector spherical harmonics (VSH) decomposition. The normal modes and the normal mode frequencies of the Proca equation in the AdS spacetime are then analytically determined. It is als… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2301.10248v1-abstract-full').style.display = 'inline'; document.getElementById('2301.10248v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2301.10248v1-abstract-full" style="display: none;"> A normal mode analysis for Proca fields in the anti-de Sitter (AdS) spacetime is given. It is found that the equations for the Proca field can be decoupled analytically. This is performed by changing the basis of the vector spherical harmonics (VSH) decomposition. The normal modes and the normal mode frequencies of the Proca equation in the AdS spacetime are then analytically determined. It is also shown that the Maxwell field can be recovered by taking the massless limit of the Proca field with care so that the nonphysical gauge modes are eliminated. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2301.10248v1-abstract-full').style.display = 'none'; document.getElementById('2301.10248v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 24 January, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> January 2023. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">6 pages</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Gen. Relativ. Gravit. 55, 5 (2023) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2301.06563">arXiv:2301.06563</a> <span> [<a href="https://arxiv.org/pdf/2301.06563">pdf</a>, <a href="https://arxiv.org/format/2301.06563">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="General Relativity and Quantum Cosmology">gr-qc</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="High Energy Physics - Theory">hep-th</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1103/PhysRevD.107.064053">10.1103/PhysRevD.107.064053 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Stability of electrically charged stars, regular black holes, quasiblack holes, and quasinonblack holes </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/gr-qc?searchtype=author&query=Masa%2C+A+D+D">Angel D. D. Masa</a>, <a href="/search/gr-qc?searchtype=author&query=Lemos%2C+J+P+S">Jos茅 P. S. Lemos</a>, <a href="/search/gr-qc?searchtype=author&query=Zanchin%2C+V+T">Vilson T. Zanchin</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2301.06563v1-abstract-short" style="display: inline;"> The stability of a class of electrically charged fluid spheres under radial perturbations is studied. Among these spheres there are regular stars, overcharged tension stars, regular black holes, quasiblack holes, and quasinonblack holes, all of which have a Reissner-Nordstr枚m exterior. We formulate the dynamical perturbed equations by following the Chandrasekhar approach and investigate the stabil… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2301.06563v1-abstract-full').style.display = 'inline'; document.getElementById('2301.06563v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2301.06563v1-abstract-full" style="display: none;"> The stability of a class of electrically charged fluid spheres under radial perturbations is studied. Among these spheres there are regular stars, overcharged tension stars, regular black holes, quasiblack holes, and quasinonblack holes, all of which have a Reissner-Nordstr枚m exterior. We formulate the dynamical perturbed equations by following the Chandrasekhar approach and investigate the stability against radial perturbations through numerical methods. It is found that (i) under certain conditions that depend on the adiabatic index of the radial perturbation, there are stable charged stars and stable tension stars; (ii) also depending on the adiabatic index there are stable regular black holes; (iii) quasiblack hole configurations formed by, e.g., charging regular pressure stars or by discharging regular tension stars, can be stable against radial perturbations for reasonable values of the adiabatic index; (iv) quasinonblack holes are unstable against radial perturbations. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2301.06563v1-abstract-full').style.display = 'none'; document.getElementById('2301.06563v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 16 January, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> January 2023. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">38 pages, 15 figures, 18 tables</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Phys. Rev. D 107, 064053 (2023) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2208.11127">arXiv:2208.11127</a> <span> [<a href="https://arxiv.org/pdf/2208.11127">pdf</a>, <a href="https://arxiv.org/format/2208.11127">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="General Relativity and Quantum Cosmology">gr-qc</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Other Condensed Matter">cond-mat.other</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="High Energy Physics - Theory">hep-th</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1103/PhysRevD.106.104008">10.1103/PhysRevD.106.104008 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Electrically charged spherical matter shells in higher dimensions: Entropy, thermodynamic stability, and the black hole limit </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/gr-qc?searchtype=author&query=Fernandes%2C+T+V">Tiago V. Fernandes</a>, <a href="/search/gr-qc?searchtype=author&query=Lemos%2C+J+P+S">Jos茅 P. S. Lemos</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2208.11127v2-abstract-short" style="display: inline;"> We study the thermodynamic properties of a static electrically charged spherical thin shell in $d$ dimensions by imposing the first law of thermodynamics on the shell. The shell is at radius $R$, inside it the spacetime is Minkowski, and outside it the spacetime is Reissner-Nordstr枚m. We obtain that the shell thermodynamics is fully described by giving two additional reduced equations of state, on… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2208.11127v2-abstract-full').style.display = 'inline'; document.getElementById('2208.11127v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2208.11127v2-abstract-full" style="display: none;"> We study the thermodynamic properties of a static electrically charged spherical thin shell in $d$ dimensions by imposing the first law of thermodynamics on the shell. The shell is at radius $R$, inside it the spacetime is Minkowski, and outside it the spacetime is Reissner-Nordstr枚m. We obtain that the shell thermodynamics is fully described by giving two additional reduced equations of state, one for the temperature and another for the electrostatic potential. We choose the equation of state for the temperature as a power law in the gravitational radius $r_+$ with exponent $a$, such that the $a=1$ case gives the temperature of a shell with black hole thermodynamic properties, and for the electrostatic potential we choose an equation of state characteristic of a Reissner-Nordstr枚m black hole spacetime. The entropy of the shell is found to be proportional to $A_+^a$, where $A_+$ is the gravitational area corresponding to $r_+$, with $a>0$. We are then able to perform the black hole limit $R=r_+$, find the Smarr formula, and recover the thermodynamics of a $d$-dimensional Reissner-Nordstr枚m black hole. We study the intrinsic thermodynamic stability of the shell with the chosen equations of state. We obtain that for $0<a\leq \frac{d-3}{d-2}$ all the configurations of the shell are thermodynamically stable, for $\frac{d-3}{d-2}<a<1$ stability depends on the mass and electric charge, and for $a>1$ all the configurations are unstable, except for the shell at its own gravitational radius, which is marginally stable. We rewrite the stability conditions in terms of laboratory variables. We find that the sufficient condition for the stability of these shells is when the isothermal electric susceptibility $蠂_{p,T}$ is positive, marginal stability happening when this quantity is infinite, and instability arising for configurations with a negative electric susceptibility. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2208.11127v2-abstract-full').style.display = 'none'; document.getElementById('2208.11127v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 24 November, 2022; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 23 August, 2022; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> August 2022. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">28 pages, 7 figures</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Phys. Rev. D 106, 104008 (2022) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2202.13113">arXiv:2202.13113</a> <span> [<a href="https://arxiv.org/pdf/2202.13113">pdf</a>, <a href="https://arxiv.org/ps/2202.13113">ps</a>, <a href="https://arxiv.org/format/2202.13113">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="General Relativity and Quantum Cosmology">gr-qc</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.5506/APhysPolBSupp.15.1-A5">10.5506/APhysPolBSupp.15.1-A5 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Notes on extraction of energy from an extremal Kerr-Newman black hole via charged particle collisions </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/gr-qc?searchtype=author&query=Hejda%2C+F">Filip Hejda</a>, <a href="/search/gr-qc?searchtype=author&query=Lemos%2C+J+P+S">Jos茅 P. S. Lemos</a>, <a href="/search/gr-qc?searchtype=author&query=Zaslavskii%2C+O+B">Oleg B. Zaslavskii</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2202.13113v1-abstract-short" style="display: inline;"> The so-called BSW effect is an idealised scenario for high-energy test particle collisions in the vicinity of black holes; if the black hole is extremal and one of the particles fine-tuned, the centre-of-mass collision energy can be arbitrarily high. It has been recently shown that the energy of escaping particles produced in this process can also be arbitrarily high in the given approximation, as… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2202.13113v1-abstract-full').style.display = 'inline'; document.getElementById('2202.13113v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2202.13113v1-abstract-full" style="display: none;"> The so-called BSW effect is an idealised scenario for high-energy test particle collisions in the vicinity of black holes; if the black hole is extremal and one of the particles fine-tuned, the centre-of-mass collision energy can be arbitrarily high. It has been recently shown that the energy of escaping particles produced in this process can also be arbitrarily high in the given approximation, as long as both the black hole and the escaping particles are charged, regardless of how small the black-hole charge might be. We revisit these results and show that they are also compatible with properties of microscopic particles for the case of motion in the equatorial plane of an extremal Kerr-Newman black hole. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2202.13113v1-abstract-full').style.display = 'none'; document.getElementById('2202.13113v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 26 February, 2022; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> February 2022. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">7 pages</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Acta Phys. Pol. B Proc. Suppl. 15, 1-A5 (2022) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2201.02203">arXiv:2201.02203</a> <span> [<a href="https://arxiv.org/pdf/2201.02203">pdf</a>, <a href="https://arxiv.org/format/2201.02203">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="General Relativity and Quantum Cosmology">gr-qc</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Cosmology and Nongalactic Astrophysics">astro-ph.CO</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="High Energy Physics - Theory">hep-th</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1103/PhysRevD.105.044058">10.1103/PhysRevD.105.044058 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Bubble universes and traversable wormholes </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/gr-qc?searchtype=author&query=Lemos%2C+J+P+S">Jos茅 P. S. Lemos</a>, <a href="/search/gr-qc?searchtype=author&query=Luz%2C+P">Paulo Luz</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2201.02203v1-abstract-short" style="display: inline;"> Bubble universes and traversable wormholes in general relativity can be realized as two sides of the same concept. To exemplify, we find, display, and study in a unified manner a Minkowski-Minkowski closed universe and a Minkowski-Minkowski traversable wormhole. By joining two 3-dimensional flat balls along a thin shell two-sphere of matter, i.e., a spherical domain wall, into a single spacetime o… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2201.02203v1-abstract-full').style.display = 'inline'; document.getElementById('2201.02203v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2201.02203v1-abstract-full" style="display: none;"> Bubble universes and traversable wormholes in general relativity can be realized as two sides of the same concept. To exemplify, we find, display, and study in a unified manner a Minkowski-Minkowski closed universe and a Minkowski-Minkowski traversable wormhole. By joining two 3-dimensional flat balls along a thin shell two-sphere of matter, i.e., a spherical domain wall, into a single spacetime one gets a Minkowski-Minkowski static closed universe, i.e., a bubble universe. By joining two 3-dimensional complements of flat balls along a thin shell two-sphere of matter, i.e., a spherical throat, into a single spacetime one gets a Minkowski-Minkowski static open universe which is a traversable wormhole. Thus, Minkowski-Minkowski bubble universes and wormholes can be seen as complementary. It is also striking that these two spacetimes have resemblances with two well-known static universes. The Minkowski-Minkowski static closed universe resembles the Einstein universe, a static closed spherical universe homogeneously filled with dust matter and with a cosmological constant. The Minkowski-Minkowski static open universe resembles the Friedmann static universe, a static open hyperbolic universe homogeneously filled with negative energy density dust and with a negative cosmological, a universe with two disjoint branes that can be considered a failed wormhole. In this light, the Einstein and Friedmann universes are also two sides of the same concept. A linear stability analysis for all these spacetimes is performed. The complementarity between bubble universes and traversable wormholes, that exists for these static spacetimes, can be can carried out for dynamical spacetimes, indicating that such a complementarity is general. The study suggests that bubble universes and traversable wormholes can be seen as coming out of the same concept, and thus, if ones exist the others should also exist. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2201.02203v1-abstract-full').style.display = 'none'; document.getElementById('2201.02203v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 6 January, 2022; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> January 2022. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">24 pages, 8 figures</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Physical Review D 105, 044058 (2022) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2112.14346">arXiv:2112.14346</a> <span> [<a href="https://arxiv.org/pdf/2112.14346">pdf</a>, <a href="https://arxiv.org/format/2112.14346">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="History and Philosophy of Physics">physics.hist-ph</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Cosmology and Nongalactic Astrophysics">astro-ph.CO</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="General Relativity and Quantum Cosmology">gr-qc</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="High Energy Physics - Theory">hep-th</span> </div> </div> <p class="title is-5 mathjax"> The Nobel prizes in physics for astrophysics and gravitation and the Nobel prize for black holes: Past, present, and future </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/gr-qc?searchtype=author&query=Lemos%2C+J+P+S">Jos茅 P. S. Lemos</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2112.14346v1-abstract-short" style="display: inline;"> We analyze the Nobel prizes in physics for astrophysics and gravitation since the establishment of the prize and highlight the 2020 Nobel prize for black holes. In addition, we comment on the names that could have received the prize in astrophysics and gravitation, and draw attention to the individuals who made outstanding contributions to black hole physics and astrophysics and should be mentione… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2112.14346v1-abstract-full').style.display = 'inline'; document.getElementById('2112.14346v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2112.14346v1-abstract-full" style="display: none;"> We analyze the Nobel prizes in physics for astrophysics and gravitation since the establishment of the prize and highlight the 2020 Nobel prize for black holes. In addition, we comment on the names that could have received the prize in astrophysics and gravitation, and draw attention to the individuals who made outstanding contributions to black hole physics and astrophysics and should be mentioned as possible and deserved recipients of the prize. We speculate about the branches of research in astrophysics and gravitation, with an emphasis on the latter, that can be contemplated in the future with a Nobel prize. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2112.14346v1-abstract-full').style.display = 'none'; document.getElementById('2112.14346v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 28 December, 2021; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> December 2021. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">26 pages, 7 figures</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Gazeta de Fisica 44(2/3), 58 (2021) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2112.03282">arXiv:2112.03282</a> <span> [<a href="https://arxiv.org/pdf/2112.03282">pdf</a>, <a href="https://arxiv.org/format/2112.03282">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="General Relativity and Quantum Cosmology">gr-qc</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="High Energy Physics - Theory">hep-th</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1103/PhysRevD.105.044017">10.1103/PhysRevD.105.044017 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Quasinormal modes of Proca fields in a Schwarzschild-AdS spacetime </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/gr-qc?searchtype=author&query=Fernandes%2C+T+V">Tiago V. Fernandes</a>, <a href="/search/gr-qc?searchtype=author&query=Hilditch%2C+D">David Hilditch</a>, <a href="/search/gr-qc?searchtype=author&query=Lemos%2C+J+P+S">Jos茅 P. S. Lemos</a>, <a href="/search/gr-qc?searchtype=author&query=Cardoso%2C+V">Vitor Cardoso</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2112.03282v2-abstract-short" style="display: inline;"> We present new results concerning the Proca massive vector field in a Schwarzschild-AdS black hole geometry. We provide a first principles analysis of Proca vector fields in this geometry using both the vector spherical harmonic (VSH) separation method and the Frolov-Krtou拧-Kubiz艌谩k-Santos (FKKS) method that separates the relevant equations in spinning geometries. The analysis in the VSH method sh… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2112.03282v2-abstract-full').style.display = 'inline'; document.getElementById('2112.03282v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2112.03282v2-abstract-full" style="display: none;"> We present new results concerning the Proca massive vector field in a Schwarzschild-AdS black hole geometry. We provide a first principles analysis of Proca vector fields in this geometry using both the vector spherical harmonic (VSH) separation method and the Frolov-Krtou拧-Kubiz艌谩k-Santos (FKKS) method that separates the relevant equations in spinning geometries. The analysis in the VSH method shows, on one hand, that it is arduous to separate the scalar-type from the vector-type polarizations of the electric sector of the Proca field, and on the other hand, it displays clearly the electric and the magnetic mode sectors. The analysis in the FKKS method is performed by taking the nonrotating limit of the Kerr-AdS spacetime, and shows that the ansatz decouples the polarizations in the electric mode sector even in the nonrotating limit. On the other hand, it captures only two of the three possible polarizations, the magnetic mode sector is missing. The reason for the absence of this polarization is related to the degeneracy of the principal tensor in static spherical symmetric spacetimes. The degrees of freedom and quasinormal modes in both separation methods of the Proca field are found. The frequencies of the quasinormal modes are also computed. For the electric mode sector in the VSH method the frequencies are found through an extension, which substitutes number coefficients by matrix coefficients, of the Horowitz-Hubeny numerical procedure, whereas for the magnetic mode sector in the VSH method and the electric sector of the FKKS method it is shown that a direct use of the procedure can be made. The values of the quasinormal mode frequencies obtained for each method are compared and showed to be in good agreement with each other. This further supports the analytical approaches presented here for the behavior of the Proca field in a Schwarzschild-AdS black hole background. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2112.03282v2-abstract-full').style.display = 'none'; document.getElementById('2112.03282v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 10 February, 2022; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 6 December, 2021; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> December 2021. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">15 pages, 4 tables, 1 appendix with 2 figures</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Phys. Rev. D 105, 044017 (2022) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2111.12109">arXiv:2111.12109</a> <span> [<a href="https://arxiv.org/pdf/2111.12109">pdf</a>, <a href="https://arxiv.org/format/2111.12109">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="General Relativity and Quantum Cosmology">gr-qc</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Cosmology and Nongalactic Astrophysics">astro-ph.CO</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="High Energy Physics - Theory">hep-th</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1103/PhysRevD.104.124076">10.1103/PhysRevD.104.124076 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Junction conditions for generalized hybrid metric-Palatini gravity with applications </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/gr-qc?searchtype=author&query=Rosa%2C+J+L">Jo茫o Lu铆s Rosa</a>, <a href="/search/gr-qc?searchtype=author&query=Lemos%2C+J+P+S">Jos茅 P. S. Lemos</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2111.12109v1-abstract-short" style="display: inline;"> The generalized hybrid metric-Palatini gravity is a theory of gravitation that has an action composed of a Lagrangian $f(R,\cal R)$, where $f$ is a function of the metric Ricci scalar $R$ and a new Ricci scalar $\cal R$ formed from a Palatini connection, plus a matter Lagrangian. This theory can be rewritten by trading the new geometric degrees of freedom of $f(R,\cal R)$ into two scalar fields,… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2111.12109v1-abstract-full').style.display = 'inline'; document.getElementById('2111.12109v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2111.12109v1-abstract-full" style="display: none;"> The generalized hybrid metric-Palatini gravity is a theory of gravitation that has an action composed of a Lagrangian $f(R,\cal R)$, where $f$ is a function of the metric Ricci scalar $R$ and a new Ricci scalar $\cal R$ formed from a Palatini connection, plus a matter Lagrangian. This theory can be rewritten by trading the new geometric degrees of freedom of $f(R,\cal R)$ into two scalar fields, $\varphi$ and $蠄$, yielding an equivalent scalar-tensor theory. Given a spacetime theory, the next step is to find solutions. To construct solutions it is often necessary to know the junction conditions between two regions at a separation hypersurface $危$, with each region being an independent solution. The junction conditions for the generalized hybrid metric-Palatini gravity are found here, in the geometric and in the scalar-tensor representations, and in addition, for each representation, the junction conditions for a matching with a thin-shell and for a smooth matching at $危$ are worked out. These junction conditions are applied to three configurations, a star, a quasistar with a black hole, and a wormhole. The star has a Minkowski interior, a thin shell at the interface with all the energy conditions being satisfied, and a Schwarzschild exterior with mass $M$, and for this theory the matching can only be performed at the shell radius given by $r_危=\frac{9M}4$, the Buchdahl radius in general relativity. The quasistar with a black hole has an interior Schwarzschild black hole surrounded by a thick shell that matches smoothly to a mass $M$ Schwarzschild exterior at the light ring, and with the energy conditions being satisfied everywhere. The wormhole has an interior that contains the throat, a thin shell at the interface, and a Schwarzschild-AdS exterior with mass $M$ and negative cosmological constant $螞$, with the null energy condition being obeyed. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2111.12109v1-abstract-full').style.display = 'none'; document.getElementById('2111.12109v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 23 November, 2021; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> November 2021. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">26 pages, 3 figures</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Phys. Rev. D 104, 124076 (2021) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2109.04477">arXiv:2109.04477</a> <span> [<a href="https://arxiv.org/pdf/2109.04477">pdf</a>, <a href="https://arxiv.org/ps/2109.04477">ps</a>, <a href="https://arxiv.org/format/2109.04477">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="General Relativity and Quantum Cosmology">gr-qc</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="High Energy Physics - Theory">hep-th</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1103/PhysRevD.105.024014">10.1103/PhysRevD.105.024014 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Extraction of energy from an extremal rotating electrovacuum black hole: Particle collisions in the equatorial plane </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/gr-qc?searchtype=author&query=Hejda%2C+F">Filip Hejda</a>, <a href="/search/gr-qc?searchtype=author&query=Lemos%2C+J+P+S">Jos茅 P. S. Lemos</a>, <a href="/search/gr-qc?searchtype=author&query=Zaslavskii%2C+O+B">Oleg B. Zaslavskii</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2109.04477v2-abstract-short" style="display: inline;"> The collisional Penrose process received much attention when Banados, Silk and West (BSW) pointed out the possibility of test-particle collisions with arbitrarily high center-of-mass energy in the vicinity of the horizon of an extremally rotating black hole. However, the energy that can be extracted from the black hole in this promising, if simplified, scenario, called the BSW effect, turned out t… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2109.04477v2-abstract-full').style.display = 'inline'; document.getElementById('2109.04477v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2109.04477v2-abstract-full" style="display: none;"> The collisional Penrose process received much attention when Banados, Silk and West (BSW) pointed out the possibility of test-particle collisions with arbitrarily high center-of-mass energy in the vicinity of the horizon of an extremally rotating black hole. However, the energy that can be extracted from the black hole in this promising, if simplified, scenario, called the BSW effect, turned out to be subject to unconditional upper bounds. And although such bounds were not found for the electrostatic variant of the process, this version is also astrophysically unfeasible, since it requires a maximally charged black hole. In order to deal with these deficiencies, we revisit the unified version of the BSW effect concerning collisions of charged particles in the equatorial plane of a rotating electrovacuum black hole spacetime. Performing a general analysis of energy extraction through this process, we explain in detail how the seemingly incompatible limiting cases arise. Furthermore, we demonstrate that the unconditional upper bounds on the extracted energy are absent for arbitrarily small values of the black hole electric charge. Therefore, our setup represents an intriguing simplified model for possible highly energetic processes happening around astrophysical black holes, which may spin fast but can have only a tiny electric charge induced via interaction with an external magnetic field. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2109.04477v2-abstract-full').style.display = 'none'; document.getElementById('2109.04477v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 27 February, 2022; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 9 September, 2021; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> September 2021. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">25 pages, 2 tables, 1 figure</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Phys. Rev. D 105, 024014 (2022) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2105.03433">arXiv:2105.03433</a> <span> [<a href="https://arxiv.org/pdf/2105.03433">pdf</a>, <a href="https://arxiv.org/format/2105.03433">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="General Relativity and Quantum Cosmology">gr-qc</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1103/PhysRevD.103.124037">10.1103/PhysRevD.103.124037 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Self-collision of a portal wormhole </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/gr-qc?searchtype=author&query=Feng%2C+J+C">Justin C. Feng</a>, <a href="/search/gr-qc?searchtype=author&query=Lemos%2C+J+P+S">Jos茅 P. S. Lemos</a>, <a href="/search/gr-qc?searchtype=author&query=Matzner%2C+R+A">Richard A. Matzner</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2105.03433v2-abstract-short" style="display: inline;"> We consider the self-collision of portals in classical general relativity. Portals are wormholes supported by a single loop of negative mass cosmic string, and being wormholes, portals have a nontrivial topology. Portals can be constructed so that the curvature is zero everywhere outside the cosmic string, with vanishing ADM mass. The conical singularities of these wormholes can be smoothed, yield… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2105.03433v2-abstract-full').style.display = 'inline'; document.getElementById('2105.03433v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2105.03433v2-abstract-full" style="display: none;"> We consider the self-collision of portals in classical general relativity. Portals are wormholes supported by a single loop of negative mass cosmic string, and being wormholes, portals have a nontrivial topology. Portals can be constructed so that the curvature is zero everywhere outside the cosmic string, with vanishing ADM mass. The conical singularities of these wormholes can be smoothed, yielding a spatial topology of $S^2 \times S^1$ with a point corresponding to spatial infinity removed. If one attempts to collide the mouths of a smoothed portal to induce self-annihilation, one naively might think that a Euclidean topology is recovered, which would violate the classical no topology change theorems. We consider a particular limit of smoothed portals supported by an anisotropic fluid, and find that while the portal mouths do not experience an acceleration as they are brought close together, a curvature singularity forms in the limit that the separation distance vanishes. We find that in general relativity, the interaction between portal mouths is not primarily gravitational in nature, but depends critically on matter interactions. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2105.03433v2-abstract-full').style.display = 'none'; document.getElementById('2105.03433v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 14 June, 2021; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 7 May, 2021; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> May 2021. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">12 pages, 8 figures</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Physical Review D 103, 124037 (2021) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2103.15832">arXiv:2103.15832</a> <span> [<a href="https://arxiv.org/pdf/2103.15832">pdf</a>, <a href="https://arxiv.org/format/2103.15832">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="General Relativity and Quantum Cosmology">gr-qc</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="High Energy Physics - Theory">hep-th</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Mathematical Physics">math-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1103/PhysRevD.103.104046">10.1103/PhysRevD.103.104046 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> All fundamental electrically charged thin shells in general relativity: From star shells to tension shell black holes and regular black holes and beyond </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/gr-qc?searchtype=author&query=Lemos%2C+J+P+S">Jos茅 P. S. Lemos</a>, <a href="/search/gr-qc?searchtype=author&query=Luz%2C+P">Paulo Luz</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2103.15832v1-abstract-short" style="display: inline;"> We classify all fundamental electrically charged thin shells in general relativity, i.e., static spherically symmetric perfect fluid thin shells with a Minkowski spacetime interior and a Reissner-Nordstr枚m spacetime exterior, characterized by the spacetime mass and electric charge. The fundamental shell can exist in three states, nonextremal, extremal, and overcharged. The nonextremal state allows… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2103.15832v1-abstract-full').style.display = 'inline'; document.getElementById('2103.15832v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2103.15832v1-abstract-full" style="display: none;"> We classify all fundamental electrically charged thin shells in general relativity, i.e., static spherically symmetric perfect fluid thin shells with a Minkowski spacetime interior and a Reissner-Nordstr枚m spacetime exterior, characterized by the spacetime mass and electric charge. The fundamental shell can exist in three states, nonextremal, extremal, and overcharged. The nonextremal state allows the shell to be located such that its radius can be outside its own gravitational radius, or can be inside its own Cauchy radius. The extremal state allows the shell to be located such that its radius can be outside its own gravitational radius, or can be inside it. The overcharged state allows the shell to be located anywhere. There is a further division, one has to specify the orientation of the shell, i.e., whether the normal out of the shell points toward increasing or decreasing radii. There is still a subdivision in the extremal state when the shell is at the gravitational radius, in that the shell can approach it from above or from below. The shell is assumed to be composed of an electrically charged perfect fluid, and the energy conditions are tested. Carter-Penrose diagrams are drawn for the shell spacetimes. There are fourteen cases in the classification of the fundamental shells, namely, nonextremal star shells, nonextremal tension shell black holes, nonextremal tension shell regular and nonregular black holes, nonextremal compact shell naked singularities, Majumdar-Papapetrou star shells, extremal tension shell singularities, extremal tension shell regular and nonregular black holes, Majumdar-Papapetrou compact shell naked singularities, Majumdar-Papapetrou shell quasiblack holes, extremal null shell quasinonblack holes, extremal null shell singularities, Majumdar-Papapetrou null shell singularities, overcharged star shells, and overcharged compact shell naked singularities. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2103.15832v1-abstract-full').style.display = 'none'; document.getElementById('2103.15832v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 29 March, 2021; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> March 2021. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">56 pages including 31 figures, plus 2 appendices including 2 figures, plus references; all together 67 pages and 33 figures</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Phys. Rev. D 103, 104046 (2021) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2101.11010">arXiv:2101.11010</a> <span> [<a href="https://arxiv.org/pdf/2101.11010">pdf</a>, <a href="https://arxiv.org/format/2101.11010">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Physics - Theory">hep-th</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Statistical Mechanics">cond-mat.stat-mech</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="General Relativity and Quantum Cosmology">gr-qc</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1103/PhysRevD.103.064069">10.1103/PhysRevD.103.064069 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Thermodynamics of $d$-dimensional Schwarzschild black holes in the canonical ensemble </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/gr-qc?searchtype=author&query=Andr%C3%A9%2C+R">Rui Andr茅</a>, <a href="/search/gr-qc?searchtype=author&query=Lemos%2C+J+P+S">Jos茅 P. S. Lemos</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2101.11010v2-abstract-short" style="display: inline;"> We study the thermodynamics of a $d$-dimensional Schwarzschild black hole in the canonical ensemble. This generalizes York's formalism to any number $d$ of dimensions. The canonical ensemble, characterized by a cavity of fixed radius $r$ and fixed temperature $T$ at the boundary, allows for two possible solutions in thermal equilibrium, a small and a large black hole. From the Euclidean action and… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2101.11010v2-abstract-full').style.display = 'inline'; document.getElementById('2101.11010v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2101.11010v2-abstract-full" style="display: none;"> We study the thermodynamics of a $d$-dimensional Schwarzschild black hole in the canonical ensemble. This generalizes York's formalism to any number $d$ of dimensions. The canonical ensemble, characterized by a cavity of fixed radius $r$ and fixed temperature $T$ at the boundary, allows for two possible solutions in thermal equilibrium, a small and a large black hole. From the Euclidean action and the path integral approach, we obtain the free energy, the thermodynamic energy, the pressure, and the entropy, of the black hole plus cavity system. The entropy is given by the Bekenstein-Hawking area law. The heat capacity shows that the smaller black hole is in unstable equilibrium and the larger is stable. The photon sphere radius divides the stability criterion. To study perturbations, a generalized free energy function is obtained that allows to understand the possible phase transitions between classical hot flat space and the black holes. The Buchdahl radius, that appears naturally in the general relativistic study of star structure, also shows up in our context, the free energy is zero when the cavity's radius has the Buchdahl radius value. Then, if the cavity's radius is smaller than the Buchdahl radius classical hot flat space can nucleate a black hole. It is also pointed out the link between the canonical analysis performed and the direct perturbation of the path integral. Since gravitational hot flat space is a quantum system made purely of gravitons it is of interest to compare the free energies of quantum hot flat space and the stable black hole to find for which ranges of $r$ and $T$ one phase predominates over the other. Phase diagrams are displayed. The density of states at a given energy is found. Further calculations and comments are carried out, notably, a connection to thin shells in $d$ spacetime dimensions which are systems that are also apt to rigorous thermodynamics. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2101.11010v2-abstract-full').style.display = 'none'; document.getElementById('2101.11010v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 19 April, 2021; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 26 January, 2021; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> January 2021. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">19 pages, 6 figures</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Phys. Rev. D 103, 064069 (2021) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2007.00665">arXiv:2007.00665</a> <span> [<a href="https://arxiv.org/pdf/2007.00665">pdf</a>, <a href="https://arxiv.org/format/2007.00665">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="General Relativity and Quantum Cosmology">gr-qc</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="High Energy Physics - Theory">hep-th</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1142/S0218271820410199">10.1142/S0218271820410199 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Compact objects in general relativity: From Buchdahl stars to quasiblack holes </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/gr-qc?searchtype=author&query=Lemos%2C+J+P+S">Jos茅 P. S. Lemos</a>, <a href="/search/gr-qc?searchtype=author&query=Zaslavskii%2C+O+B">Oleg B. Zaslavskii</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2007.00665v2-abstract-short" style="display: inline;"> A Buchdahl star is a highly compact star for which the boundary radius $R$ obeys $R=\frac98 r_+$, where $r_+$ is the gravitational radius of the star itself. A quasiblack hole is a maximum compact star, or more generically a maximum compact object, for which the boundary radius $R$ obeys $R=r_+$. Quasiblack holes are objects on the verge of becoming black holes. Continued gravitational collapse en… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2007.00665v2-abstract-full').style.display = 'inline'; document.getElementById('2007.00665v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2007.00665v2-abstract-full" style="display: none;"> A Buchdahl star is a highly compact star for which the boundary radius $R$ obeys $R=\frac98 r_+$, where $r_+$ is the gravitational radius of the star itself. A quasiblack hole is a maximum compact star, or more generically a maximum compact object, for which the boundary radius $R$ obeys $R=r_+$. Quasiblack holes are objects on the verge of becoming black holes. Continued gravitational collapse ends in black holes and has to be handled with the Oppenheimer-Snyder formalism. Quasistatic contraction ends in a quasiblack hole and should be treated with appropriate techniques. Quasiblack holes, not black holes, are the real descendants of Mitchell and Laplace dark stars. Quasiblack holes have many interesting properties. We develop the concept of a quasiblack hole, give several examples of such an object, define what it is, draw its Carter-Penrose diagram, study its pressure properties, obtain its mass formula, derive the entropy of a nonextremal quasiblack hole, and through an extremal quasiblack hole give a solution to the puzzling entropy of extremal black holes. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2007.00665v2-abstract-full').style.display = 'none'; document.getElementById('2007.00665v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 16 September, 2020; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 1 July, 2020; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> July 2020. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">25 pages, 7 figures</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> International Journal of Modern Physics D 29, 2041019 (2020) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2006.10050">arXiv:2006.10050</a> <span> [<a href="https://arxiv.org/pdf/2006.10050">pdf</a>, <a href="https://arxiv.org/format/2006.10050">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Physics - Theory">hep-th</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="General Relativity and Quantum Cosmology">gr-qc</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1103/PhysRevD.102.024006">10.1103/PhysRevD.102.024006 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Thermodynamics of five-dimensional Schwarzschild black holes in the canonical ensemble </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/gr-qc?searchtype=author&query=Andr%C3%A9%2C+R">Rui Andr茅</a>, <a href="/search/gr-qc?searchtype=author&query=Lemos%2C+J+P+S">Jos茅 P. S. Lemos</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2006.10050v1-abstract-short" style="display: inline;"> We study the thermodynamics of a five-dimensional Schwarzschild black hole in the canonical ensemble using York's formalism. Inside a cavity of fixed size $r$ and fixed temperature $T$, there is a threshold at $蟺r T = 1$ above which a black hole can be in thermal equilibrium. This thermal equilibrium can be achieved for two specific black holes, a small black hole of horizon radius $r_{+1}$, and a… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2006.10050v1-abstract-full').style.display = 'inline'; document.getElementById('2006.10050v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2006.10050v1-abstract-full" style="display: none;"> We study the thermodynamics of a five-dimensional Schwarzschild black hole in the canonical ensemble using York's formalism. Inside a cavity of fixed size $r$ and fixed temperature $T$, there is a threshold at $蟺r T = 1$ above which a black hole can be in thermal equilibrium. This thermal equilibrium can be achieved for two specific black holes, a small black hole of horizon radius $r_{+1}$, and a large black hole of radius $r_{+2}$. In five dimensions, the radii $r_{+1}$ and $r_{+2}$ have an exact expression. Through the path integral formalism and the partition function, one obtains the action and the free energy. This leads to the thermal energy and entropy of the system, the latter turning out to be given by the Bekenstein-Hawking area law $S = \frac{A_{+}}{4}$, where $A_+$ is the black hole's surface area. The heat capacity is positive when the heat bath is placed at a radius $r$ that is equal or less than the photonic orbit, implying thermodynamic stability. This means that the small black hole is unstable and the large one is stable. A generalized free energy is used to show that it is feasible that classical hot flat space transits through $r_{+1}$ to settle at the stable $r_{+2}$. Remarkably, the free energy of the larger $r_{+2}$ black hole is zero when the cavity radius is equal to the Buchdahl radius. The relation to the instabilities that arise due to perturbations in the path integral in the instanton solution is mentioned. Quantum hot flat space has negative free energy and we find the conditions for which the large black hole, quantum hot flat space, or both are the ground state. The corresponding phase diagram is displayed. Using the density of states $谓$ at a given energy $E$ we also find that the entropy of the large black hole $r_{+2}$. In addition, we make the connection between the five-dimensional thermodynamics and York's four-dimensional results. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2006.10050v1-abstract-full').style.display = 'none'; document.getElementById('2006.10050v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 17 June, 2020; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> June 2020. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">11 pages, 3 figures</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Phys. Rev. D 102, 024006 (2020) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2005.14211">arXiv:2005.14211</a> <span> [<a href="https://arxiv.org/pdf/2005.14211">pdf</a>, <a href="https://arxiv.org/format/2005.14211">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="General Relativity and Quantum Cosmology">gr-qc</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="High Energy Physics - Theory">hep-th</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Mathematical Physics">math-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1016/j.aop.2021.168497">10.1016/j.aop.2021.168497 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Maximal extension of the Schwarzschild metric: From Painlev茅-Gullstrand to Kruskal-Szekeres </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/gr-qc?searchtype=author&query=Lemos%2C+J+P+S">Jos茅 P. S. Lemos</a>, <a href="/search/gr-qc?searchtype=author&query=Silva%2C+D+L+F+G">Diogo L. F. G. Silva</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2005.14211v1-abstract-short" style="display: inline;"> We find a specific coordinate system that goes from the Painlev茅-Gullstrand partial extension to the Kruskal-Szekeres maximal extension and thus exhibit the maximal extension of the Schwarzschild metric in a unified picture. We do this by adopting two time coordinates, one being the proper time of a congruence of outgoing timelike geodesics, the other being the proper time of a congruence of ingoi… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2005.14211v1-abstract-full').style.display = 'inline'; document.getElementById('2005.14211v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2005.14211v1-abstract-full" style="display: none;"> We find a specific coordinate system that goes from the Painlev茅-Gullstrand partial extension to the Kruskal-Szekeres maximal extension and thus exhibit the maximal extension of the Schwarzschild metric in a unified picture. We do this by adopting two time coordinates, one being the proper time of a congruence of outgoing timelike geodesics, the other being the proper time of a congruence of ingoing timelike geodesics, both parameterized by the same energy per unit mass $E$. $E$ is in the range $1\leq E<\infty$ with the limit $E=\infty$ yielding the Kruskal-Szekeres maximal extension. So, through such an integrated description one sees that the Kruskal-Szekeres solution belongs to this family of extensions parameterized by $E$. Our family of extensions is different from the Novikov-Lema卯tre family parameterized also by the energy $E$ of timelike geodesics, with the Novikov extension holding for $0<E<1$ and being maximal, and the Lema卯tre extension holding for $1\leq E<\infty$ and being partial, not maximal, and moreover its $E=\infty$ limit evanescing in a Minkowski spacetime rather than ending in the Kruskal-Szekeres spacetime. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2005.14211v1-abstract-full').style.display = 'none'; document.getElementById('2005.14211v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 28 May, 2020; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> May 2020. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">18 pages, 7 figures</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Annals of Physics 430, 168497 (2021) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2004.06117">arXiv:2004.06117</a> <span> [<a href="https://arxiv.org/pdf/2004.06117">pdf</a>, <a href="https://arxiv.org/ps/2004.06117">ps</a>, <a href="https://arxiv.org/format/2004.06117">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="General Relativity and Quantum Cosmology">gr-qc</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="High Energy Physics - Theory">hep-th</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1103/PhysRevD.102.044060">10.1103/PhysRevD.102.044060 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Gravitational field of a pit and maximal mass defects </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/gr-qc?searchtype=author&query=Lemos%2C+J+P+S">Jos茅 P. S. Lemos</a>, <a href="/search/gr-qc?searchtype=author&query=Zaslavskii%2C+O+B">Oleg B. Zaslavskii</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2004.06117v2-abstract-short" style="display: inline;"> A general relativistic solution, composed of a Zel'dovich-Letelier interior made of radial strings matched through a spherical thin shell at radius $r_0$ to an exterior Schwarzschild solution with mass $m$, is presented. It is the Zel'dovich-Letelier-Schwarzschild star. When the radius $r_0$ of the star is shrunk to its gravitational radius $2m$, the solutions have interesting properties. There ar… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2004.06117v2-abstract-full').style.display = 'inline'; document.getElementById('2004.06117v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2004.06117v2-abstract-full" style="display: none;"> A general relativistic solution, composed of a Zel'dovich-Letelier interior made of radial strings matched through a spherical thin shell at radius $r_0$ to an exterior Schwarzschild solution with mass $m$, is presented. It is the Zel'dovich-Letelier-Schwarzschild star. When the radius $r_0$ of the star is shrunk to its gravitational radius $2m$, the solutions have interesting properties. There are solutions with $m=0$ and $r_0=0$ that obey $\frac{2m}{r_0}=1$. The solutions have a horizon, but are not black holes, they are quasiblack holes, though atypical. The proper mass $m_p$ of the interior is nonzero and made of one string. Hence, a Minkowski exterior space hides an interior with matter in a pit. These are the pit solutions and show a maximal mass defect. There are two classes of pit solutions, one a finite string and the other a semi-infinite one. These pits are really string pits, that can be seen as Wheeler bags of gold, albeit squashed bags. There is another class, which is a compact stringy star at the $\frac{2m}{r_0}=1$ limit with $m$ nonzero. It is a typical quasiblack hole and it has maximal mass defect. Generically pit solutions with $\frac{2m}{r_0}=1$ and $m=0$ can exist with maximal mass defects. The Zel'dovich-Letelier-Schwarzschild star at the $r_0=2m$ limit is an instance of it. These three classes of static solutions yield the same spectrum of solutions that appear in critical gravitational collapse, there are solutions that yield naked null singularities, which here are the two string pit classes, there are solutions that yield black holes, which here are represented by the compact stringy stars at the quasiblack hole limit, and the solutions that disperse away in critical collapse here are the static Zel'dovich-Letelier-Schwarzschild stars. Thermodynamics of the string pit and stringy star quasiblack hole solutions is provided, and other connections are mentioned. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2004.06117v2-abstract-full').style.display = 'none'; document.getElementById('2004.06117v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 15 September, 2020; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 13 April, 2020; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> April 2020. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">10 pages, 3 figures, 1 table</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Physical Review D 102, 044060 (2020) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2003.00090">arXiv:2003.00090</a> <span> [<a href="https://arxiv.org/pdf/2003.00090">pdf</a>, <a href="https://arxiv.org/format/2003.00090">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="General Relativity and Quantum Cosmology">gr-qc</span> </div> </div> <p class="title is-5 mathjax"> Stability of Kerr black holes in generalized hybrid metric-Palatini gravity </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/gr-qc?searchtype=author&query=Rosa%2C+J+L">Jo茫o Lu铆s Rosa</a>, <a href="/search/gr-qc?searchtype=author&query=Lemos%2C+J+P+S">Jos茅 P. S. Lemos</a>, <a href="/search/gr-qc?searchtype=author&query=Lobo%2C+F+S+N">Francisco S. N. Lobo</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2003.00090v1-abstract-short" style="display: inline;"> It is shown that the Kerr solution exists in the generalized hybrid metric-Palatini gravity theory and that for certain choices of the function $f(R,\mathcal R)$ that characterizes the theory, the Kerr solution can be stable against perturbations on the scalar degree of freedom of the theory. We start by verifying which are the most general conditions on the function $f(R,\mathcal R)$ that allow f… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2003.00090v1-abstract-full').style.display = 'inline'; document.getElementById('2003.00090v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2003.00090v1-abstract-full" style="display: none;"> It is shown that the Kerr solution exists in the generalized hybrid metric-Palatini gravity theory and that for certain choices of the function $f(R,\mathcal R)$ that characterizes the theory, the Kerr solution can be stable against perturbations on the scalar degree of freedom of the theory. We start by verifying which are the most general conditions on the function $f(R,\mathcal R)$ that allow for the general relativistic Kerr solution to also be a solution of this theory. We perform a scalar perturbation in the trace of the metric tensor, which in turn imposes a perturbation in both the Ricci and Palatini scalar curvatures. To first order in the perturbation, the equations of motion, namely the field equations and the equation that relates the Ricci and the Palatini curvature scalars, can be rewritten in terms of a fourth-order wave equation for the perturbation $未R$ which can be factorized into two second-order massive wave equations for the same variable. The usual ansatz and separation methods are applied and stability bounds on the effective mass of the Ricci scalar perturbation are obtained. These stability regimes are studied case by case and specific forms of the function $f(R,\mathcal R)$ that allow for a stable Kerr solution to exist within the perturbation regime studied are obtained. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2003.00090v1-abstract-full').style.display = 'none'; document.getElementById('2003.00090v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 28 February, 2020; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> March 2020. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">11 pages, 1 figure</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Phys. Rev. D 101, 044055 (2020) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1912.08833">arXiv:1912.08833</a> <span> [<a href="https://arxiv.org/pdf/1912.08833">pdf</a>, <a href="https://arxiv.org/format/1912.08833">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="General Relativity and Quantum Cosmology">gr-qc</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="High Energy Physics - Theory">hep-th</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1088/1475-7516/2020/03/035">10.1088/1475-7516/2020/03/035 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Lensing and shadow of a black hole surrounded by a heavy accretion disk </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/gr-qc?searchtype=author&query=Cunha%2C+P+V+P">Pedro V. P. Cunha</a>, <a href="/search/gr-qc?searchtype=author&query=Eir%C3%B3%2C+N+A">Nelson A. Eir贸</a>, <a href="/search/gr-qc?searchtype=author&query=Herdeiro%2C+C+A+R">Carlos A. R. Herdeiro</a>, <a href="/search/gr-qc?searchtype=author&query=Lemos%2C+J+P+S">Jos茅 P. S. Lemos</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1912.08833v2-abstract-short" style="display: inline;"> We consider a static, axially symmetric spacetime describing the superposition of a Schwarzschild black hole (BH) with a thin and heavy accretion disk. The BH-disk configuration is a solution of the Einstein field equations within the Weyl class. The disk is sourced by a distributional energy-momentum tensor and it is located at the equatorial plane. It can be interpreted as two streams of counter… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1912.08833v2-abstract-full').style.display = 'inline'; document.getElementById('1912.08833v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1912.08833v2-abstract-full" style="display: none;"> We consider a static, axially symmetric spacetime describing the superposition of a Schwarzschild black hole (BH) with a thin and heavy accretion disk. The BH-disk configuration is a solution of the Einstein field equations within the Weyl class. The disk is sourced by a distributional energy-momentum tensor and it is located at the equatorial plane. It can be interpreted as two streams of counter-rotating particles, yielding a total vanishing angular momentum. The phenomenology of the composed system depends on two parameters: the fraction of the total mass in the disk, $m$, and the location of the inner edge of the disk, $a$. We start by determining the sub-region of the space of parameters wherein the solution is physical, by requiring the velocity of the disk particles to be sub-luminal and real. Then, we study the null geodesic flow by performing backwards ray-tracing under two scenarios. In the first scenario the composed system is illuminated by the disk and in the second scenario the composed system is illuminated by a far-away celestial sphere. Both cases show that, as $m$ grows, the shadow becomes more prolate. Additionally, the first scenario makes clear that as $m$ grows, for fixed $a$, the geometrically thin disk appears optically enlarged, i.e., thicker, when observed from the equatorial plane. This is to due to light rays that are bent towards the disk, when backwards ray traced. In the second scenario, these light rays can cross the disk (which is assumed to be transparent) and may oscillate up to a few times before reaching the far away celestial sphere. Consequently, an almost equatorial observer sees different patches of the sky near the equatorial plane, as a chaotic "mirage". As $m\rightarrow 0$ one recovers the standard test, i.e., negligible mass, disk appearance. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1912.08833v2-abstract-full').style.display = 'none'; document.getElementById('1912.08833v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 27 December, 2019; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 18 December, 2019; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> December 2019. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">24 pages, 15 figures</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> JCAP 03 (2020) 035 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1912.08354">arXiv:1912.08354</a> <span> [<a href="https://arxiv.org/pdf/1912.08354">pdf</a>, <a href="https://arxiv.org/format/1912.08354">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="History and Philosophy of Physics">physics.hist-ph</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="General Relativity and Quantum Cosmology">gr-qc</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="High Energy Physics - Theory">hep-th</span> </div> </div> <p class="title is-5 mathjax"> Einstein and Eddington and the eclipse in Principe: Celebration and science 100 years after </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/gr-qc?searchtype=author&query=Lemos%2C+J+P+S">Jos茅 P. S. Lemos</a>, <a href="/search/gr-qc?searchtype=author&query=Herdeiro%2C+C+A+R">Carlos A. R. Herdeiro</a>, <a href="/search/gr-qc?searchtype=author&query=Cardoso%2C+V">Vitor Cardoso</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1912.08354v1-abstract-short" style="display: inline;"> On May 29, 1919, at Ro莽a Sundy, Principe island, Eddington confirms Einstein's general relativity theory for the first time by photographing stars behind the obscured Sun during a total eclipse. History was made. At Sobral, Eddington's astronomer colleagues photograph the same eclipse and also conclude that light from distant stars suffers a deflection when passing by the gravitational field of th… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1912.08354v1-abstract-full').style.display = 'inline'; document.getElementById('1912.08354v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1912.08354v1-abstract-full" style="display: none;"> On May 29, 1919, at Ro莽a Sundy, Principe island, Eddington confirms Einstein's general relativity theory for the first time by photographing stars behind the obscured Sun during a total eclipse. History was made. At Sobral, Eddington's astronomer colleagues photograph the same eclipse and also conclude that light from distant stars suffers a deflection when passing by the gravitational field of the Sun, in accordance with general relativity. With the confirmation of general relativity, a theory of gravitation at a fundamental level, physics became, once and for all, relativist and its future was outlined. The first world war had finished a few months before and the deep wounds between nations were yet to heal. Science wanted to be above it all showing that people could be united by a common goal. This year, the 100 years of this achievement was commemorated with the scientific conference "From Einstein and Eddington to LIGO: 100 years of gravitational light deflection" in Principe to celebrate this landmark event. We report here on this conference of celebration. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1912.08354v1-abstract-full').style.display = 'none'; document.getElementById('1912.08354v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 17 December, 2019; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> December 2019. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">12 pages, 4 figures</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Gazeta de Fisica 42(4/5), 26 (2019) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1912.05587">arXiv:1912.05587</a> <span> [<a href="https://arxiv.org/pdf/1912.05587">pdf</a>, <a href="https://arxiv.org/format/1912.05587">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="History and Philosophy of Physics">physics.hist-ph</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="General Relativity and Quantum Cosmology">gr-qc</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="High Energy Physics - Theory">hep-th</span> </div> </div> <p class="title is-5 mathjax"> Shadow of the Moon and general relativity: Einstein, Dyson, Eddington and the 1919 light deflection </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/gr-qc?searchtype=author&query=Lemos%2C+J+P+S">Jos茅 P. S. Lemos</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1912.05587v1-abstract-short" style="display: inline;"> The eclipse of the Sun of 1919 was fundamental in the development of physics and earns a high place in the history of science. Several players took part in this adventure. The most important are Einstein, Dyson, Eddington, the Sun, the Moon, Sobral, and Principe. Einstein's theory of gravitation, general relativity, had the prediction that the gravitational field of the Sun deflects an incoming li… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1912.05587v1-abstract-full').style.display = 'inline'; document.getElementById('1912.05587v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1912.05587v1-abstract-full" style="display: none;"> The eclipse of the Sun of 1919 was fundamental in the development of physics and earns a high place in the history of science. Several players took part in this adventure. The most important are Einstein, Dyson, Eddington, the Sun, the Moon, Sobral, and Principe. Einstein's theory of gravitation, general relativity, had the prediction that the gravitational field of the Sun deflects an incoming light ray from a background star on its way to Earth. The calculation gave that the shift in the star's position was 1.75 arcseconds for light rays passing at the Sun's rim. So to test it definitely it was necessary to be in the right places on May 29, 1919, the day of the eclipse. That indeed happened, with a Royal Greenwich Observatory team composed of Crommelin and Davidson that went to Sobral, and that was led at a distance by the Astronomer Royal Frank Dyson, and with Eddington of Cambridge University that went to Principe with his assistant Cottingham. The adventure is fascinating, from the preparations, to the day of the eclipse, the data analysis, the results, and the history that has been made. It confirmed general relativity, and marked an epoch that helped in delineating science in the post eclipse era up to now and into the future. This year of 2019 we are celebrating this enormous breakthrough <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1912.05587v1-abstract-full').style.display = 'none'; document.getElementById('1912.05587v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 11 December, 2019; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> December 2019. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">63 pages, 39 figures</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Revista Brasileira de Ensino de Fisica 41 suppl 1, e20190260 (2019) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1911.01959">arXiv:1911.01959</a> <span> [<a href="https://arxiv.org/pdf/1911.01959">pdf</a>, <a href="https://arxiv.org/format/1911.01959">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="History and Philosophy of Physics">physics.hist-ph</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="General Relativity and Quantum Cosmology">gr-qc</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="High Energy Physics - Theory">hep-th</span> </div> </div> <p class="title is-5 mathjax"> Einstein and Eddington and the consequences of general relativity: Black holes and gravitational waves </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/gr-qc?searchtype=author&query=Lemos%2C+J+P+S">Jos茅 P. S. Lemos</a>, <a href="/search/gr-qc?searchtype=author&query=Herdeiro%2C+C+A+R">Carlos A. R. Herdeiro</a>, <a href="/search/gr-qc?searchtype=author&query=Cardoso%2C+V">Vitor Cardoso</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1911.01959v1-abstract-short" style="display: inline;"> For the celebrations of the 100 years of the observations undertaken by Eddington at the island of Principe and collaborators at Sobral during a total solar eclipse in May 29, 1919, which have confirmed Einstein's theory of general relativity through the deflection of the incoming light from distant stars due to the spacetime curvature caused by the Sun, we highlight the main aspects of the theory… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1911.01959v1-abstract-full').style.display = 'inline'; document.getElementById('1911.01959v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1911.01959v1-abstract-full" style="display: none;"> For the celebrations of the 100 years of the observations undertaken by Eddington at the island of Principe and collaborators at Sobral during a total solar eclipse in May 29, 1919, which have confirmed Einstein's theory of general relativity through the deflection of the incoming light from distant stars due to the spacetime curvature caused by the Sun, we highlight the main aspects of the theory, its tests and applications, focusing on some of its outstanding consequences. These are black holes, the object par excellence of general relativity, and gravitational waves, the gravitational probe for the distant Universe. We also point out some open issues. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1911.01959v1-abstract-full').style.display = 'none'; document.getElementById('1911.01959v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 5 November, 2019; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> November 2019. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">16 pages, 2 figures</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Gazeta de Fisica 42(2), 36 (2019) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1908.07778">arXiv:1908.07778</a> <span> [<a href="https://arxiv.org/pdf/1908.07778">pdf</a>, <a href="https://arxiv.org/format/1908.07778">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="General Relativity and Quantum Cosmology">gr-qc</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="High Energy Physics - Theory">hep-th</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1103/PhysRevD.101.104056">10.1103/PhysRevD.101.104056 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Cosmological phase space of generalized hybrid metric-Palatini theories of gravity </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/gr-qc?searchtype=author&query=Rosa%2C+J+L">Jo茫o L. Rosa</a>, <a href="/search/gr-qc?searchtype=author&query=Carloni%2C+S">Sante Carloni</a>, <a href="/search/gr-qc?searchtype=author&query=Lemos%2C+J+P+S">Jos茅 P. S. Lemos</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1908.07778v2-abstract-short" style="display: inline;"> Using a dynamical system approach we study the cosmological phase space of the generalized hybrid metric-Palatini gravity theory, characterized by the function $f\left(R,\mathcal R\right)$, where $R$ is the metric scalar curvature and $\mathcal R$ the Palatini scalar curvature of the spacetime. We formulate the propagation equations of the suitable dimensionless variables that describe FLRW univer… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1908.07778v2-abstract-full').style.display = 'inline'; document.getElementById('1908.07778v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1908.07778v2-abstract-full" style="display: none;"> Using a dynamical system approach we study the cosmological phase space of the generalized hybrid metric-Palatini gravity theory, characterized by the function $f\left(R,\mathcal R\right)$, where $R$ is the metric scalar curvature and $\mathcal R$ the Palatini scalar curvature of the spacetime. We formulate the propagation equations of the suitable dimensionless variables that describe FLRW universes as an autonomous system. The fixed points are obtained for four different forms of the function $f\left(R,\mathcal R\right)$, and the behavior of the cosmic scale factor $a(t)$ is computed. We show that due to the structure of the system, no global attractors can be present and also that two different classes of solutions for the scale factor $a(t)$ exist. Numerical integrations of the dynamical system equations are performed with initial conditions consistent with the observations of the cosmological parameters of the present state of the Universe. In addition, using a redefinition of the dynamic variables, we are able to compute interesting solutions for static universes. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1908.07778v2-abstract-full').style.display = 'none'; document.getElementById('1908.07778v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 1 June, 2020; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 21 August, 2019; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> August 2019. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">26 pages, 6 figures, 6 tables</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Phys. Rev. D 101, 104056 (2020) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1905.05239">arXiv:1905.05239</a> <span> [<a href="https://arxiv.org/pdf/1905.05239">pdf</a>, <a href="https://arxiv.org/format/1905.05239">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Physics - Theory">hep-th</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="General Relativity and Quantum Cosmology">gr-qc</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Mathematical Physics">math-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1103/PhysRevD.99.125013">10.1103/PhysRevD.99.125013 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Thermodynamics and entropy of self-gravitating matter shells and black holes in $d$ dimensions </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/gr-qc?searchtype=author&query=Andr%C3%A9%2C+R">Rui Andr茅</a>, <a href="/search/gr-qc?searchtype=author&query=Lemos%2C+J+P+S">Jos茅 P. S. Lemos</a>, <a href="/search/gr-qc?searchtype=author&query=Quinta%2C+G+M">Gon莽alo M. Quinta</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1905.05239v1-abstract-short" style="display: inline;"> The thermodynamic properties of self-gravitating spherical thin matter shells an black holes in $d>4$ dimensions are studied, extending previous analysis for $d=4$. The shell joins a Minkowski interior to a Tangherlini exterior, i.e., a Schwarzschild exterior in $d$ dimensions, with $d\geqslant4$, The junction conditions alone together with the first law of thermodynamics enable one to establish t… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1905.05239v1-abstract-full').style.display = 'inline'; document.getElementById('1905.05239v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1905.05239v1-abstract-full" style="display: none;"> The thermodynamic properties of self-gravitating spherical thin matter shells an black holes in $d>4$ dimensions are studied, extending previous analysis for $d=4$. The shell joins a Minkowski interior to a Tangherlini exterior, i.e., a Schwarzschild exterior in $d$ dimensions, with $d\geqslant4$, The junction conditions alone together with the first law of thermodynamics enable one to establish that the entropy of the thin shell depends only on its own gravitational radius. Endowing the shell with a power-law temperature equation of state allows to establish a precise form for the entropy and to perform a thermodynamic stability analysis for the shell. An interesting case is when the shell's temperature has the Hawking form, i.e., it is inversely proportional to the shell's gravitational radius. It is shown in this case that the shell's heat capacity is positive, and thus there is stability, for shells with radii in-between their own gravitational radius and the photonic radius, i.e., the radius of circular photon orbits, reproducing unexpectedly York's thermodynamic stability criterion for a $d=4$ black hole in the canonical ensemble. Additionally, the Euler equation for the matter shell is derived, the Bekenstein and holographic entropy bounds are studied, and the large $d$ limit is analyzed. Within this formalism the thermodynamic properties of black holes can be studied too. Putting the shell at its own gravitational radius, i.e., in the black hole situation, obliges one to choose precisely the Hawking temperature for the shell which in turn yields the Bekenstein-Hawking entropy. The stability analysis implies that the black hole is thermodynamically stable substantiating that in this configuration our system and York's canonical ensemble black hole are indeed the same system. Also relevant is the derivation in a surprising way of the Smarr formula for black holes in $d$ dimensions. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1905.05239v1-abstract-full').style.display = 'none'; document.getElementById('1905.05239v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 13 May, 2019; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> May 2019. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">12 pages, 3 figures</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Phys. Rev. D 99, 125013 (2019) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1904.00260">arXiv:1904.00260</a> <span> [<a href="https://arxiv.org/pdf/1904.00260">pdf</a>, <a href="https://arxiv.org/ps/1904.00260">ps</a>, <a href="https://arxiv.org/format/1904.00260">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="General Relativity and Quantum Cosmology">gr-qc</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Cosmology and Nongalactic Astrophysics">astro-ph.CO</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="High Energy Physics - Theory">hep-th</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1016/j.aop.2019.02.010">10.1016/j.aop.2019.02.010 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Covariant action for bouncing cosmologies in modified Gauss-Bonnet gravity </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/gr-qc?searchtype=author&query=Terrucha%2C+I">In锚s Terrucha</a>, <a href="/search/gr-qc?searchtype=author&query=Vernieri%2C+D">Daniele Vernieri</a>, <a href="/search/gr-qc?searchtype=author&query=Lemos%2C+J+P+S">Jos茅 P. S. Lemos</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1904.00260v1-abstract-short" style="display: inline;"> Cyclic universes with bouncing solutions are candidates for solving the big bang initial singularity problem. Here we seek bouncing solutions in a modified Gauss-Bonnet gravity theory, of the type $R+f(G)$, where $R$ is the Ricci scalar, $G$ is the Gauss-Bonnet term, and $f$ some function of it. In finding such a bouncing solution we resort to a technique that reduces the order of the differential… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1904.00260v1-abstract-full').style.display = 'inline'; document.getElementById('1904.00260v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1904.00260v1-abstract-full" style="display: none;"> Cyclic universes with bouncing solutions are candidates for solving the big bang initial singularity problem. Here we seek bouncing solutions in a modified Gauss-Bonnet gravity theory, of the type $R+f(G)$, where $R$ is the Ricci scalar, $G$ is the Gauss-Bonnet term, and $f$ some function of it. In finding such a bouncing solution we resort to a technique that reduces the order of the differential equations of the $R+f(G)$ theory to second order equations. As general relativity is a theory whose equations are of second order, this order reduction technique enables one to find solutions which are perturbatively close to general relativity. We also build the covariant action of the order reduced theory. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1904.00260v1-abstract-full').style.display = 'none'; document.getElementById('1904.00260v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 30 March, 2019; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> April 2019. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">8 pages</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Annals of Physics 404 (2019) 39 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1901.00218">arXiv:1901.00218</a> <span> [<a href="https://arxiv.org/pdf/1901.00218">pdf</a>, <a href="https://arxiv.org/ps/1901.00218">ps</a>, <a href="https://arxiv.org/format/1901.00218">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="General Relativity and Quantum Cosmology">gr-qc</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1007/JHEP04(2019)139">10.1007/JHEP04(2019)139 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Spontaneously broken symmetry restoration of quantum fields in the vicinity of neutral and electrically charged black holes </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/gr-qc?searchtype=author&query=Quinta%2C+G+M">Gon莽alo M. Quinta</a>, <a href="/search/gr-qc?searchtype=author&query=Flachi%2C+A">Antonino Flachi</a>, <a href="/search/gr-qc?searchtype=author&query=Lemos%2C+J+P+S">Jos茅 P. S. Lemos</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1901.00218v1-abstract-short" style="display: inline;"> We consider the restoration of a spontaneously broken symmetry of an interacting quantum scalar field around neutral, i.e., Schwarzschild, and electrically charged, i.e., Reissner-Nordstr枚m, black holes in four dimensions. This is done through a semiclassical self-consistent procedure, by solving the system of non-linear coupled equations describing the dynamics of the background field and the vac… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1901.00218v1-abstract-full').style.display = 'inline'; document.getElementById('1901.00218v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1901.00218v1-abstract-full" style="display: none;"> We consider the restoration of a spontaneously broken symmetry of an interacting quantum scalar field around neutral, i.e., Schwarzschild, and electrically charged, i.e., Reissner-Nordstr枚m, black holes in four dimensions. This is done through a semiclassical self-consistent procedure, by solving the system of non-linear coupled equations describing the dynamics of the background field and the vacuum polarization. The black hole at its own horizon generates an indefinitely high temperature which decreases to the Hawking temperature at infinity. Due to the high temperature in its vicinity, there forms a bubble around the black hole in which the scalar field can only assume a value equal to zero, a minimum of energy. Thus, in this region the symmetry of the energy and the field is preserved. At the bubble radius, there is a phase transition in the value of the scalar field due to a spontaneous symmetry breaking mechanism. Indeed, outside the bubble radius the temperature is low enough such that the scalar field settles with a nonzero value in a new energy minimum, indicating a breaking of the symmetry in this outer region. Conversely, there is symmetry restoration from the outer region to the inner bubble close to the horizon. Specific properties that emerge from different black hole electric charges are also noteworthy. It is found that colder black holes, i.e., more charged ones, have a smaller bubble length of restored symmetry. In the extremal case the bubble has zero length, i.e., there is no bubble. Additionally, for colder black holes, it becomes harder to excite the quantum field modes, so the vacuum polarization has smaller values. In the extremal case, the black hole temperature is zero and the vacuum polarization is never excited. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1901.00218v1-abstract-full').style.display = 'none'; document.getElementById('1901.00218v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 1 January, 2019; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> January 2019. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">16 pages, 4 figures</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> JHEP 04 (2019) 139 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1811.06587">arXiv:1811.06587</a> <span> [<a href="https://arxiv.org/pdf/1811.06587">pdf</a>, <a href="https://arxiv.org/ps/1811.06587">ps</a>, <a href="https://arxiv.org/format/1811.06587">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="History and Philosophy of Physics">physics.hist-ph</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="General Relativity and Quantum Cosmology">gr-qc</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="High Energy Physics - Theory">hep-th</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Popular Physics">physics.pop-ph</span> </div> </div> <p class="title is-5 mathjax"> The black hole fifty years after: Genesis of the name </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/gr-qc?searchtype=author&query=Herdeiro%2C+C+A+R">Carlos A. R. Herdeiro</a>, <a href="/search/gr-qc?searchtype=author&query=Lemos%2C+J+P+S">Jos茅 P. S. Lemos</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1811.06587v2-abstract-short" style="display: inline;"> Black holes are extreme spacetime deformations where even light is imprisoned. There is an extensive astrophysical evidence for the real and abundant existence of these prisons of matter and light in the Universe. Mathematically, black holes are described by solutions of the field equations of the theory of general relativity, the first of which was published in 1916 by Karl Schwarzschild. Another… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1811.06587v2-abstract-full').style.display = 'inline'; document.getElementById('1811.06587v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1811.06587v2-abstract-full" style="display: none;"> Black holes are extreme spacetime deformations where even light is imprisoned. There is an extensive astrophysical evidence for the real and abundant existence of these prisons of matter and light in the Universe. Mathematically, black holes are described by solutions of the field equations of the theory of general relativity, the first of which was published in 1916 by Karl Schwarzschild. Another highly relevant solution, representing a rotating black hole, was found by Roy Kerr in 1963. It was only much after the publication of the Schwarzschild solution, however, that the term black hole was employed to describe these objects. Who invented it? Conventional wisdom attributes the origin of the term to the prominent North American physicist John Wheeler who first adopted it in a general audience article published in 1968. This, however, is just one side of a story that begins two hundred years before in an Indian prison colloquially known as the Black Hole of Calcutta. Robert Dicke, also a distinguished physicist and colleague of Wheeler at Princeton University, aware of the prison's tragedy began, around 1960, to compare gravitationally completely collapsed stars to the black hole of Calcutta. The whole account thus suggests reconsidering who indeed coined the name black hole and commends acknowledging its definitive birth to a partnership between Wheeler and Dicke. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1811.06587v2-abstract-full').style.display = 'none'; document.getElementById('1811.06587v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 12 December, 2019; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 15 November, 2018; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> November 2018. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">17 pages, 3 figures</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Gazeta de Fisica 41(2), 2 (2018) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1808.08975">arXiv:1808.08975</a> <span> [<a href="https://arxiv.org/pdf/1808.08975">pdf</a>, <a href="https://arxiv.org/format/1808.08975">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="General Relativity and Quantum Cosmology">gr-qc</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="High Energy Physics - Theory">hep-th</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1103/PhysRevD.98.064054">10.1103/PhysRevD.98.064054 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Wormholes in generalized hybrid metric-Palatini gravity obeying the matter null energy condition everywhere </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/gr-qc?searchtype=author&query=Rosa%2C+J+L">Jo茫o Lu铆s Rosa</a>, <a href="/search/gr-qc?searchtype=author&query=Lemos%2C+J+P+S">Jos茅 P. S. Lemos</a>, <a href="/search/gr-qc?searchtype=author&query=Lobo%2C+F+S+N">Francisco S. N. Lobo</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1808.08975v1-abstract-short" style="display: inline;"> Wormhole solutions in a generalized hybrid metric-Palatini matter theory, given by a gravitational Lagrangian $f\left(R,\cal{R}\right)$, where $R$ is the metric Ricci scalar, and $\mathcal{R}$ is a Palatini scalar curvature defined in terms of an independent connection, and a matter Lagrangian, are found. The solutions are worked in the scalar-tensor representation of the theory, where the Palatin… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1808.08975v1-abstract-full').style.display = 'inline'; document.getElementById('1808.08975v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1808.08975v1-abstract-full" style="display: none;"> Wormhole solutions in a generalized hybrid metric-Palatini matter theory, given by a gravitational Lagrangian $f\left(R,\cal{R}\right)$, where $R$ is the metric Ricci scalar, and $\mathcal{R}$ is a Palatini scalar curvature defined in terms of an independent connection, and a matter Lagrangian, are found. The solutions are worked in the scalar-tensor representation of the theory, where the Palatini field is traded for two scalars, $\varphi$ and $蠄$, and the gravitational term $R$ is maintained. The main interest in the solutions found is that the matter field obeys the null energy condition (NEC) everywhere, including the throat and up to infinity, so that there is no need for exotic matter. The wormhole geometry with its flaring out at the throat is supported by the higher-order curvature terms, or equivalently, by the two fundamental scalar fields, which either way can be interpreted as a gravitational fluid. Thus, in this theory, in building a wormhole, it is possible to exchange the exoticity of matter by the exoticity of the gravitational sector. The specific wormhole displayed, built to obey the matter NEC from the throat to infinity, has three regions, namely, an interior region containing the throat, a thin shell of matter, and a vacuum Schwarzschild anti-de Sitter (AdS) exterior. For hybrid metric-Palatini matter theories this wormhole solution is the first where the NEC for the matter is verified for the entire spacetime keeping the solution under asymptotic control. The existence of this type of solutions is in line with the idea that traversable wormholes bore by additional fundamental gravitational fields, here disguised as scalar fields, can be found without exotic matter. Concomitantly, the somewhat concocted architecture needed to assemble a complete wormhole solution for the whole spacetime may imply that in this class of theories such solutions are scarce. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1808.08975v1-abstract-full').style.display = 'none'; document.getElementById('1808.08975v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 27 August, 2018; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> August 2018. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">12 pages, 2 figures</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Phys. Rev. D 98, 064054 (2018) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1808.07316">arXiv:1808.07316</a> <span> [<a href="https://arxiv.org/pdf/1808.07316">pdf</a>, <a href="https://arxiv.org/format/1808.07316">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="General Relativity and Quantum Cosmology">gr-qc</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1103/PhysRevD.99.104001">10.1103/PhysRevD.99.104001 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Cosmology of $f(R, \Box R)$ gravity </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/gr-qc?searchtype=author&query=Carloni%2C+S">Sante Carloni</a>, <a href="/search/gr-qc?searchtype=author&query=Rosa%2C+J+L">Jo茫o Lu铆s Rosa</a>, <a href="/search/gr-qc?searchtype=author&query=Lemos%2C+J+P+S">Jos茅 P. S. Lemos</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1808.07316v2-abstract-short" style="display: inline;"> Using dynamical system analysis, we explore the cosmology of theories of order up to eight order of the form $f(R, \Box R)$. The phase space of these cosmology reveals that higher-order terms can have a dramatic influence on the evolution of the cosmology, avoiding the onset of finite time singularities. We also confirm and extend some of results which were obtained in the past for this class of t… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1808.07316v2-abstract-full').style.display = 'inline'; document.getElementById('1808.07316v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1808.07316v2-abstract-full" style="display: none;"> Using dynamical system analysis, we explore the cosmology of theories of order up to eight order of the form $f(R, \Box R)$. The phase space of these cosmology reveals that higher-order terms can have a dramatic influence on the evolution of the cosmology, avoiding the onset of finite time singularities. We also confirm and extend some of results which were obtained in the past for this class of theories. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1808.07316v2-abstract-full').style.display = 'none'; document.getElementById('1808.07316v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 2 April, 2019; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 22 August, 2018; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> August 2018. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">26 pages, 7 tables, 8 figures, extended and improved version of the paper</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Phys. Rev. D 99, 104001 (2019) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1807.00036">arXiv:1807.00036</a> <span> [<a href="https://arxiv.org/pdf/1807.00036">pdf</a>, <a href="https://arxiv.org/ps/1807.00036">ps</a>, <a href="https://arxiv.org/format/1807.00036">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="General Relativity and Quantum Cosmology">gr-qc</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Cosmology and Nongalactic Astrophysics">astro-ph.CO</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="High Energy Physics - Theory">hep-th</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1140/epjc/s10052-018-6006-7">10.1140/epjc/s10052-018-6006-7 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Stratified scalar field theories of gravitation with self-energy term and effective particle Lagrangian </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/gr-qc?searchtype=author&query=Bragan%C3%A7a%2C+D+P+L">Diogo P. L. Bragan莽a</a>, <a href="/search/gr-qc?searchtype=author&query=Lemos%2C+J+P+S">Jos茅 P. S. Lemos</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1807.00036v1-abstract-short" style="display: inline;"> We construct a general stratified scalar theory of gravitation from a field equation that accounts for the self-interaction of the field and a particle Lagrangian, and calculate its post-Newtonian parameters. Using this general framework, we analyze several specific scalar theories of gravitation and check their predictions for the solar system post-Newtonian effects. </span> <span class="abstract-full has-text-grey-dark mathjax" id="1807.00036v1-abstract-full" style="display: none;"> We construct a general stratified scalar theory of gravitation from a field equation that accounts for the self-interaction of the field and a particle Lagrangian, and calculate its post-Newtonian parameters. Using this general framework, we analyze several specific scalar theories of gravitation and check their predictions for the solar system post-Newtonian effects. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1807.00036v1-abstract-full').style.display = 'none'; document.getElementById('1807.00036v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 29 June, 2018; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> July 2018. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">12 pages</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Eur. Phys. J. C 78:, 533 (2018) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1806.07910">arXiv:1806.07910</a> <span> [<a href="https://arxiv.org/pdf/1806.07910">pdf</a>, <a href="https://arxiv.org/ps/1806.07910">ps</a>, <a href="https://arxiv.org/format/1806.07910">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Physics - Theory">hep-th</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="General Relativity and Quantum Cosmology">gr-qc</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1016/j.physletb.2018.08.075">10.1016/j.physletb.2018.08.075 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Black hole thermodynamics with the cosmological constant as independent variable: Bridge between the enthalpy and the Euclidean path integral approaches </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/gr-qc?searchtype=author&query=Lemos%2C+J+P+S">Jos茅 P. S. Lemos</a>, <a href="/search/gr-qc?searchtype=author&query=Zaslavskii%2C+O+B">Oleg B. Zaslavskii</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1806.07910v1-abstract-short" style="display: inline;"> Viewing the cosmological constant $螞<0$ as an independent variable, we consider the thermodynamics of the Schwarzschild black hole in an anti-de Sitter (AdS) background. For this system, there is one approach which regards the enthalpy as the master thermodynamic variable and makes sense if one considers the vacuum pressure due to the cosmological constant acting in the volume inside the horizon a… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1806.07910v1-abstract-full').style.display = 'inline'; document.getElementById('1806.07910v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1806.07910v1-abstract-full" style="display: none;"> Viewing the cosmological constant $螞<0$ as an independent variable, we consider the thermodynamics of the Schwarzschild black hole in an anti-de Sitter (AdS) background. For this system, there is one approach which regards the enthalpy as the master thermodynamic variable and makes sense if one considers the vacuum pressure due to the cosmological constant acting in the volume inside the horizon and the outer size of the system is not restricted. From this approach a first law of thermodynamics emerges naturally. There is yet another approach based on the Euclidean action principle and its path integral that puts the black hole inside a cavity, defines a quasilocal energy at the cavity's boundary, and from which a first law of thermodynamics in a different version also emerges naturally. The first approach has affinities with critical phenomena in condensed matter physics and the second approach is an ingredient necessary for the construction of quantum gravity. The bridge between the two approaches is carried out rigorously, putting thus the enthalpic thermodynamics with $螞$ as independent variable on the same footing as the quasilocal energy approach. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1806.07910v1-abstract-full').style.display = 'none'; document.getElementById('1806.07910v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 20 June, 2018; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> June 2018. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">4 pages</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Physics Letters B 786 (2018) 296 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1806.05195">arXiv:1806.05195</a> <span> [<a href="https://arxiv.org/pdf/1806.05195">pdf</a>, <a href="https://arxiv.org/format/1806.05195">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="General Relativity and Quantum Cosmology">gr-qc</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="High Energy Physics - Theory">hep-th</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1088/1361-6382/ab0587">10.1088/1361-6382/ab0587 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Black holes, gravitational waves and fundamental physics: a roadmap </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/gr-qc?searchtype=author&query=Barack%2C+L">Leor Barack</a>, <a href="/search/gr-qc?searchtype=author&query=Cardoso%2C+V">Vitor Cardoso</a>, <a href="/search/gr-qc?searchtype=author&query=Nissanke%2C+S">Samaya Nissanke</a>, <a href="/search/gr-qc?searchtype=author&query=Sotiriou%2C+T+P">Thomas P. Sotiriou</a>, <a href="/search/gr-qc?searchtype=author&query=Askar%2C+A">Abbas Askar</a>, <a href="/search/gr-qc?searchtype=author&query=Belczynski%2C+K">Krzysztof Belczynski</a>, <a href="/search/gr-qc?searchtype=author&query=Bertone%2C+G">Gianfranco Bertone</a>, <a href="/search/gr-qc?searchtype=author&query=Bon%2C+E">Edi Bon</a>, <a href="/search/gr-qc?searchtype=author&query=Blas%2C+D">Diego Blas</a>, <a href="/search/gr-qc?searchtype=author&query=Brito%2C+R">Richard Brito</a>, <a href="/search/gr-qc?searchtype=author&query=Bulik%2C+T">Tomasz Bulik</a>, <a href="/search/gr-qc?searchtype=author&query=Burrage%2C+C">Clare Burrage</a>, <a href="/search/gr-qc?searchtype=author&query=Byrnes%2C+C+T">Christian T. Byrnes</a>, <a href="/search/gr-qc?searchtype=author&query=Caprini%2C+C">Chiara Caprini</a>, <a href="/search/gr-qc?searchtype=author&query=Chernyakova%2C+M">Masha Chernyakova</a>, <a href="/search/gr-qc?searchtype=author&query=Chrusciel%2C+P">Piotr Chrusciel</a>, <a href="/search/gr-qc?searchtype=author&query=Colpi%2C+M">Monica Colpi</a>, <a href="/search/gr-qc?searchtype=author&query=Ferrari%2C+V">Valeria Ferrari</a>, <a href="/search/gr-qc?searchtype=author&query=Gaggero%2C+D">Daniele Gaggero</a>, <a href="/search/gr-qc?searchtype=author&query=Gair%2C+J">Jonathan Gair</a>, <a href="/search/gr-qc?searchtype=author&query=Garcia-Bellido%2C+J">Juan Garcia-Bellido</a>, <a href="/search/gr-qc?searchtype=author&query=Hassan%2C+S+F">S. F. Hassan</a>, <a href="/search/gr-qc?searchtype=author&query=Heisenberg%2C+L">Lavinia Heisenberg</a>, <a href="/search/gr-qc?searchtype=author&query=Hendry%2C+M">Martin Hendry</a>, <a href="/search/gr-qc?searchtype=author&query=Heng%2C+I+S">Ik Siong Heng</a> , et al. (181 additional authors not shown) </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1806.05195v4-abstract-short" style="display: inline;"> The grand challenges of contemporary fundamental physics---dark matter, dark energy, vacuum energy, inflation and early universe cosmology, singularities and the hierarchy problem---all involve gravity as a key component. And of all gravitational phenomena, black holes stand out in their elegant simplicity, while harbouring some of the most remarkable predictions of General Relativity: event horiz… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1806.05195v4-abstract-full').style.display = 'inline'; document.getElementById('1806.05195v4-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1806.05195v4-abstract-full" style="display: none;"> The grand challenges of contemporary fundamental physics---dark matter, dark energy, vacuum energy, inflation and early universe cosmology, singularities and the hierarchy problem---all involve gravity as a key component. And of all gravitational phenomena, black holes stand out in their elegant simplicity, while harbouring some of the most remarkable predictions of General Relativity: event horizons, singularities and ergoregions. The hitherto invisible landscape of the gravitational Universe is being unveiled before our eyes: the historical direct detection of gravitational waves by the LIGO-Virgo collaboration marks the dawn of a new era of scientific exploration. Gravitational-wave astronomy will allow us to test models of black hole formation, growth and evolution, as well as models of gravitational-wave generation and propagation. It will provide evidence for event horizons and ergoregions, test the theory of General Relativity itself, and may reveal the existence of new fundamental fields. The synthesis of these results has the potential to radically reshape our understanding of the cosmos and of the laws of Nature. The purpose of this work is to present a concise, yet comprehensive overview of the state of the art in the relevant fields of research, summarize important open problems, and lay out a roadmap for future progress. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1806.05195v4-abstract-full').style.display = 'none'; document.getElementById('1806.05195v4-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 1 February, 2019; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 13 June, 2018; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> June 2018. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">White Paper for the COST action "Gravitational Waves, Black Holes, and Fundamental Physics", 272 pages, 12 figures; v4: updated references and author list. Overall improvements and corrections. To appear in Classical and Quantum Gravity</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1712.08171">arXiv:1712.08171</a> <span> [<a href="https://arxiv.org/pdf/1712.08171">pdf</a>, <a href="https://arxiv.org/ps/1712.08171">ps</a>, <a href="https://arxiv.org/format/1712.08171">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="General Relativity and Quantum Cosmology">gr-qc</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="High Energy Physics - Theory">hep-th</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1103/PhysRevD.97.025023">10.1103/PhysRevD.97.025023 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Quantum vacuum polarization around a Reissner-Nordstr枚m black hole in five dimensions </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/gr-qc?searchtype=author&query=Quinta%2C+G+M">Gon莽alo M. Quinta</a>, <a href="/search/gr-qc?searchtype=author&query=Flachi%2C+A">Antonino Flachi</a>, <a href="/search/gr-qc?searchtype=author&query=Lemos%2C+J+P+S">Jos茅 P. S. Lemos</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1712.08171v2-abstract-short" style="display: inline;"> WKB approximation methods are applied to the case of a massive scalar field around a 5-dimensional Reissner-Nordstr枚m black hole. The divergences are explicitly isolated and the cancellation against the Schwinger-De Witt counter-terms proven. The resulting finite quantity is evaluated for different values of the free parameters, namely the black hole mass and charge, and the scalar field mass. We… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1712.08171v2-abstract-full').style.display = 'inline'; document.getElementById('1712.08171v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1712.08171v2-abstract-full" style="display: none;"> WKB approximation methods are applied to the case of a massive scalar field around a 5-dimensional Reissner-Nordstr枚m black hole. The divergences are explicitly isolated and the cancellation against the Schwinger-De Witt counter-terms proven. The resulting finite quantity is evaluated for different values of the free parameters, namely the black hole mass and charge, and the scalar field mass. We thus extend our previous results on quantum vacuum polarization effects for uncharged asymptotically flat higher dimensional black holes to electrically charged black holes. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1712.08171v2-abstract-full').style.display = 'none'; document.getElementById('1712.08171v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 1 February, 2018; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 21 December, 2017; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> December 2017. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">6 pages, 3 figures</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Phys. Rev. D 97, 025023 (2018) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1712.03236">arXiv:1712.03236</a> <span> [<a href="https://arxiv.org/pdf/1712.03236">pdf</a>, <a href="https://arxiv.org/ps/1712.03236">ps</a>, <a href="https://arxiv.org/format/1712.03236">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="General Relativity and Quantum Cosmology">gr-qc</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="High Energy Physics - Theory">hep-th</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Mathematical Physics">math-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1103/PhysRevD.97.064008">10.1103/PhysRevD.97.064008 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Black hole mass formula in the membrane paradigm </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/gr-qc?searchtype=author&query=Lemos%2C+J+P+S">Jos茅 P. S. Lemos</a>, <a href="/search/gr-qc?searchtype=author&query=Zaslavskii%2C+O+B">Oleg B. Zaslavskii</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1712.03236v2-abstract-short" style="display: inline;"> The membrane paradigm approach adopts a timelike surface, stretched out off the null event horizon, to study several important black hole properties. We use this powerful tool to give a direct derivation of the black hole mass formula in the static and stationary cases without and with electric field. Since here the membrane is a self-gravitating material system we go beyond the usual applicabilit… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1712.03236v2-abstract-full').style.display = 'inline'; document.getElementById('1712.03236v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1712.03236v2-abstract-full" style="display: none;"> The membrane paradigm approach adopts a timelike surface, stretched out off the null event horizon, to study several important black hole properties. We use this powerful tool to give a direct derivation of the black hole mass formula in the static and stationary cases without and with electric field. Since here the membrane is a self-gravitating material system we go beyond the usual applicability on test particles and test fields of the paradigm. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1712.03236v2-abstract-full').style.display = 'none'; document.getElementById('1712.03236v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 25 March, 2018; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 8 December, 2017; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> December 2017. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">27 pages, no figures. The revised version emphasizes the novelty of the result within the membrane paradigm. Other minor corrections</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Phys. Rev. D 97, 064008 (2018) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1709.08637">arXiv:1709.08637</a> <span> [<a href="https://arxiv.org/pdf/1709.08637">pdf</a>, <a href="https://arxiv.org/ps/1709.08637">ps</a>, <a href="https://arxiv.org/format/1709.08637">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Physics - Theory">hep-th</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="General Relativity and Quantum Cosmology">gr-qc</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Mathematical Physics">math-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1103/PhysRevD.96.084068">10.1103/PhysRevD.96.084068 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Unified approach to the entropy of an extremal rotating BTZ black hole: Thin shells and horizon limits </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/gr-qc?searchtype=author&query=Lemos%2C+J+P+S">Jos茅 P. S. Lemos</a>, <a href="/search/gr-qc?searchtype=author&query=Minamitsuji%2C+M">Masato Minamitsuji</a>, <a href="/search/gr-qc?searchtype=author&query=Zaslavskii%2C+O+B">Oleg B. Zaslavskii</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1709.08637v2-abstract-short" style="display: inline;"> Using a thin shell, the first law of thermodynamics, and a unified approach, we study the thermodymanics and find the entropy of a (2+1)-dimensional extremal rotating Ba帽ados-Teitelbom-Zanelli (BTZ) black hole. The shell in (2+1) dimensions, i.e., a ring, is taken to be circularly symmetric and rotating, with the inner region being a ground state of the anti-de Sitter (AdS) spacetime and the outer… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1709.08637v2-abstract-full').style.display = 'inline'; document.getElementById('1709.08637v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1709.08637v2-abstract-full" style="display: none;"> Using a thin shell, the first law of thermodynamics, and a unified approach, we study the thermodymanics and find the entropy of a (2+1)-dimensional extremal rotating Ba帽ados-Teitelbom-Zanelli (BTZ) black hole. The shell in (2+1) dimensions, i.e., a ring, is taken to be circularly symmetric and rotating, with the inner region being a ground state of the anti-de Sitter (AdS) spacetime and the outer region being the rotating BTZ spacetime. The extremal BTZ rotating black hole can be obtained in three different ways depending on the way the shell approaches its own gravitational or horizon radius. These ways are explicitly worked out. The resulting three cases give that the BTZ black hole entropy is either the Bekenstein-Hawking entropy, $S=\frac{A_+}{4G}$, or it is an arbitrary function of $A_+$, $S=S(A_+)$, where $A_+=2蟺r_+$ is the area, i.e., the perimeter, of the event horizon in (2+1) dimensions. We speculate that the entropy of an extremal black hole should obey $0\leq S(A_+)\leq\frac{A_+}{4G}$. We also show that the contributions from the various thermodynamic quantities, namely, the mass, the circular velocity, and the temperature, for the entropy in all three cases are distinct. This study complements the previous studies in thin shell thermodynamics and entropy for BTZ black holes. It also corroborates the results found for a (3+1)-dimensional extremal electrically charged Reissner-Nordstr枚m black hole. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1709.08637v2-abstract-full').style.display = 'none'; document.getElementById('1709.08637v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 1 November, 2017; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 25 September, 2017; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> September 2017. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">8 pages, 1 table, no figure</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Phys. Rev. D 96, 084068 (2017) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1704.07840">arXiv:1704.07840</a> <span> [<a href="https://arxiv.org/pdf/1704.07840">pdf</a>, <a href="https://arxiv.org/ps/1704.07840">ps</a>, <a href="https://arxiv.org/format/1704.07840">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="General Relativity and Quantum Cosmology">gr-qc</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="High Energy Physics - Theory">hep-th</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1103/PhysRevD.95.104040">10.1103/PhysRevD.95.104040 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Plethora of relativistic charged spheres: The full spectrum of Guilfoyle's static, electrically charged spherical solutions </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/gr-qc?searchtype=author&query=Lemos%2C+J+P+S">Jos茅 P. S. Lemos</a>, <a href="/search/gr-qc?searchtype=author&query=Zanchin%2C+V+T">Vilson T. Zanchin</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1704.07840v2-abstract-short" style="display: inline;"> We show that Guilfoyle's exact solutions of the Einstein-Maxwell equations for spherical symmetric static electrically charged matter with a Reissner-Nordstr枚m exterior possess a bewildering plethora of different types of solutions. For the parameter space of the solutions we use two normalized variables, $q^2/R^2$ and $r_0/R$, where $q$ is the total electric charge, $r_0$ is the radius of the obj… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1704.07840v2-abstract-full').style.display = 'inline'; document.getElementById('1704.07840v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1704.07840v2-abstract-full" style="display: none;"> We show that Guilfoyle's exact solutions of the Einstein-Maxwell equations for spherical symmetric static electrically charged matter with a Reissner-Nordstr枚m exterior possess a bewildering plethora of different types of solutions. For the parameter space of the solutions we use two normalized variables, $q^2/R^2$ and $r_0/R$, where $q$ is the total electric charge, $r_0$ is the radius of the object, and $R$ is a length representing the square root of the inverse energy density of the matter. The two other parameters, the mass $m$ and the Guilfoyle parameter $a$, both dependent on $q$, $r_0$ and $R$, are analyzed in detail. The full parameter space of solutions $q^2/R^2\times r_0/R$ is explored with the corresponding types of solutions being identified and analyzed. The different types of solutions are regular charged stars, including charged dust stars and stars saturating the Buchdahl-Andr茅asson bound, quasiblack holes, regular charged black holes with a de Sitter core, regular black holes with a core of phantom charged matter, other exotic regular black holes, Schwarzschild stars, Schwarzschild black holes, Kasner spacetimes, pointlike and planar naked singularities, and the Minkowski spacetime. Allowing for $q^2<0$, in which case it is not possible to interpret $q$ as electric charge, also yields new solutions, some of which are interesting and regular, others are singular. Some of these types of solutions as well as the matter properties have been previously found and studied, here the full spectrum being presented in a unified manner. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1704.07840v2-abstract-full').style.display = 'none'; document.getElementById('1704.07840v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 16 September, 2020; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 25 April, 2017; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> April 2017. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">23 pages, 4 figures</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Physical Review D 95, 104040 (2017) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1703.03335">arXiv:1703.03335</a> <span> [<a href="https://arxiv.org/pdf/1703.03335">pdf</a>, <a href="https://arxiv.org/format/1703.03335">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="General Relativity and Quantum Cosmology">gr-qc</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Cosmology and Nongalactic Astrophysics">astro-ph.CO</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="High Energy Physics - Theory">hep-th</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1103/PhysRevD.95.124035">10.1103/PhysRevD.95.124035 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Cosmological solutions in generalized hybrid metric-Palatini gravity </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/gr-qc?searchtype=author&query=Rosa%2C+J+L">Jo茫o L. Rosa</a>, <a href="/search/gr-qc?searchtype=author&query=Carloni%2C+S">Sante Carloni</a>, <a href="/search/gr-qc?searchtype=author&query=Lemos%2C+J+P+S">Jos茅 P. S. Lemos</a>, <a href="/search/gr-qc?searchtype=author&query=Lobo%2C+F+S+N">Francisco S. N. Lobo</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1703.03335v2-abstract-short" style="display: inline;"> We construct exact solutions representing a Friedmann-Lema卯tre-Robsertson-Walker (FLRW) universe in a generalized hybrid metric-Palatini theory. By writing the gravitational action in a scalar-tensor representation, the new solutions are obtained by either making an ansatz on the scale factor or on the effective potential. Among other relevant results, we show that it is possible to obtain exponen… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1703.03335v2-abstract-full').style.display = 'inline'; document.getElementById('1703.03335v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1703.03335v2-abstract-full" style="display: none;"> We construct exact solutions representing a Friedmann-Lema卯tre-Robsertson-Walker (FLRW) universe in a generalized hybrid metric-Palatini theory. By writing the gravitational action in a scalar-tensor representation, the new solutions are obtained by either making an ansatz on the scale factor or on the effective potential. Among other relevant results, we show that it is possible to obtain exponentially expanding solutions for flat universes even when the cosmology is not purely vacuum. We then derive the classes of actions for the original theory which generate these solutions. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1703.03335v2-abstract-full').style.display = 'none'; document.getElementById('1703.03335v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 14 July, 2017; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 9 March, 2017; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> March 2017. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">14 pages, 17 figures</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Phys. Rev. D 95, 124035 (2017) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1701.02348">arXiv:1701.02348</a> <span> [<a href="https://arxiv.org/pdf/1701.02348">pdf</a>, <a href="https://arxiv.org/ps/1701.02348">ps</a>, <a href="https://arxiv.org/format/1701.02348">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Physics - Theory">hep-th</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="General Relativity and Quantum Cosmology">gr-qc</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1103/PhysRevD.95.044003">10.1103/PhysRevD.95.044003 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Thermodynamics of extremal rotating thin shells in an extremal BTZ spacetime and the extremal black hole entropy </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/gr-qc?searchtype=author&query=Lemos%2C+J+P+S">Jos茅 P. S. Lemos</a>, <a href="/search/gr-qc?searchtype=author&query=Minamitsuji%2C+M">Masato Minamitsuji</a>, <a href="/search/gr-qc?searchtype=author&query=Zaslavskii%2C+O+B">Oleg B. Zaslavskii</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1701.02348v2-abstract-short" style="display: inline;"> In a (2+1)-dimensional spacetime with a negative cosmological constant, the thermodynamics and the entropy of an extremal rotating thin shell, i.e., an extremal rotating ring, are investigated. The outer and inner regions are taken to be the Ba帽ados-Teitelbom-Zanelli (BTZ) spacetime and the vacuum ground state anti-de Sitter (AdS) spacetime, respectively. By applying the first law of thermodynamic… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1701.02348v2-abstract-full').style.display = 'inline'; document.getElementById('1701.02348v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1701.02348v2-abstract-full" style="display: none;"> In a (2+1)-dimensional spacetime with a negative cosmological constant, the thermodynamics and the entropy of an extremal rotating thin shell, i.e., an extremal rotating ring, are investigated. The outer and inner regions are taken to be the Ba帽ados-Teitelbom-Zanelli (BTZ) spacetime and the vacuum ground state anti-de Sitter (AdS) spacetime, respectively. By applying the first law of thermodynamics to the extremal shell one shows that its entropy is an arbitrary function of the gravitational area $A_+$ alone, $S=S(A_+)$. When the shell approaches its own gravitational radius $r_+$ and turns into an extremal rotating BTZ black hole, it is found that the entropy of the spacetime remains such a function of $A_+$. It is thus vindicated, that extremal black holes, here extremal BTZ black holes, have different properties from the corresponding nonextremal black holes, which have the Bekenstein-Hawking entropy $S(A_+)= \frac{A_+}{4G}$, where $G$ is the gravitational constant. It is argued that for the extremal case $0\leq S(A_+)\leq \frac{A_+}{4G}$. Thus, rather than having just two entropies for extremal black holes, as previous results debated, 0 and $\frac{A_+}{4G}$, it is shown that extremal black holes may have a continuous range of entropies, limited by precisely those two entropies. Surely, the entropy that a particular extremal black hole picks must depend on past processes, notably on how it was formed. It is also found a remarkable relation between the third law of thermodynamics and the impossibility for a massive body to reach the velocity of light. In the procedure, it becomes clear that there are two distinct angular velocities for the shell, the mechanical and thermodynamic angular velocities. In passing, we clarify, for a static spacetime with a thermal shell, the meaning of the Tolman temperature formula at a generic radius and at the shell. (Abridged version). <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1701.02348v2-abstract-full').style.display = 'none'; document.getElementById('1701.02348v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 21 February, 2017; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 9 January, 2017; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> January 2017. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">14 pages, no figures</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Physical Review D 95, 044003 (2017) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1609.06794">arXiv:1609.06794</a> <span> [<a href="https://arxiv.org/pdf/1609.06794">pdf</a>, <a href="https://arxiv.org/format/1609.06794">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="General Relativity and Quantum Cosmology">gr-qc</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="High Energy Physics - Theory">hep-th</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1103/PhysRevD.94.105001">10.1103/PhysRevD.94.105001 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Black Hole Quantum Vacuum Polarization in Higher Dimensions </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/gr-qc?searchtype=author&query=Flachi%2C+A">Antonino Flachi</a>, <a href="/search/gr-qc?searchtype=author&query=Quinta%2C+G+M">Gon莽alo M. Quinta</a>, <a href="/search/gr-qc?searchtype=author&query=Lemos%2C+J+P+S">Jos茅 P. S. Lemos</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1609.06794v1-abstract-short" style="display: inline;"> The goal of this paper is to extend to higher dimensionality the methods and computations of vacuum polarization effects in black hole spacetimes. We focus our attention on the case of five dimensional Schwarzschild-Tangherlini black holes, for which we adapt the general method initially developed by Candelas and later refined by Anderson and others. We make use of point splitting regularization a… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1609.06794v1-abstract-full').style.display = 'inline'; document.getElementById('1609.06794v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1609.06794v1-abstract-full" style="display: none;"> The goal of this paper is to extend to higher dimensionality the methods and computations of vacuum polarization effects in black hole spacetimes. We focus our attention on the case of five dimensional Schwarzschild-Tangherlini black holes, for which we adapt the general method initially developed by Candelas and later refined by Anderson and others. We make use of point splitting regularization and of the WKB approximation to extract the divergences occuring in the coincidence limit of the Green function and, after calculating the counter-terms using the Schwinger - De Witt expansion, we explicitly prove the cancellation of the divergences and the regularity of the vacuum polarization once counter-terms are added up. We finally handle numerically the renormalized expression of the vacuum polarization. As a check on the method we also prove the regularity of the vacuum polarization in the six dimensional case in the large mass limit. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1609.06794v1-abstract-full').style.display = 'none'; document.getElementById('1609.06794v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 21 September, 2016; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> September 2016. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">14 pages, 2 Figures</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Phys. Rev. D 94, 105001 (2016) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1608.08360">arXiv:1608.08360</a> <span> [<a href="https://arxiv.org/pdf/1608.08360">pdf</a>, <a href="https://arxiv.org/ps/1608.08360">ps</a>, <a href="https://arxiv.org/format/1608.08360">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="General Relativity and Quantum Cosmology">gr-qc</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> </div> </div> <p class="title is-5 mathjax"> Gravitational fields with sources: From compact objects to black holes </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/gr-qc?searchtype=author&query=Lemos%2C+J+P+S">Jos茅 P. S. Lemos</a>, <a href="/search/gr-qc?searchtype=author&query=Pani%2C+P">Paolo Pani</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1608.08360v1-abstract-short" style="display: inline;"> We report on the Parallel Session BH4 "Gravitational fields with sources: From compact objects to black holes" of the 14th Marcel Grossmann Meeting held at Sapienza University of Rome in 2015. </span> <span class="abstract-full has-text-grey-dark mathjax" id="1608.08360v1-abstract-full" style="display: none;"> We report on the Parallel Session BH4 "Gravitational fields with sources: From compact objects to black holes" of the 14th Marcel Grossmann Meeting held at Sapienza University of Rome in 2015. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1608.08360v1-abstract-full').style.display = 'none'; document.getElementById('1608.08360v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 30 August, 2016; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> August 2016. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">Report of the BH4 Parallel Session of the 14th Marcel Grossmann Meeting - MG14</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1604.00495">arXiv:1604.00495</a> <span> [<a href="https://arxiv.org/pdf/1604.00495">pdf</a>, <a href="https://arxiv.org/ps/1604.00495">ps</a>, <a href="https://arxiv.org/format/1604.00495">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="General Relativity and Quantum Cosmology">gr-qc</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1103/PhysRevD.93.124073">10.1103/PhysRevD.93.124073 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Vacuum polarization in asymptotically Lifshitz black holes </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/gr-qc?searchtype=author&query=Quinta%2C+G+M">Gon莽alo M. Quinta</a>, <a href="/search/gr-qc?searchtype=author&query=Flachi%2C+A">Antonino Flachi</a>, <a href="/search/gr-qc?searchtype=author&query=Lemos%2C+J+P+S">Jos茅 P. S. Lemos</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1604.00495v1-abstract-short" style="display: inline;"> There has been considerable interest in applying the gauge/gravity duality to condensed matter theories with particular attention being devoted to gravity duals (Lifshitz spacetimes) of theories that exhibit anisotropic scaling. In this context, black hole solutions with Lifshitz asymptotics have also been constructed aiming at incorporating finite temperature effects. The goal here is to look at… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1604.00495v1-abstract-full').style.display = 'inline'; document.getElementById('1604.00495v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1604.00495v1-abstract-full" style="display: none;"> There has been considerable interest in applying the gauge/gravity duality to condensed matter theories with particular attention being devoted to gravity duals (Lifshitz spacetimes) of theories that exhibit anisotropic scaling. In this context, black hole solutions with Lifshitz asymptotics have also been constructed aiming at incorporating finite temperature effects. The goal here is to look at quantum polarization effects in these spacetimes, and to this aim, we develop a way to compute the coincidence limit of the Green's function for massive, non-minimally coupled scalar fields, adapting to the present situation the analysis developed for the case of asymptotically anti de Sitter black holes. The basics are similar to previous calculations, however in the Lifshitz case one needs to extend previous results to include a more general form for the metric and dependence on the dynamical exponent. All formulae are shown to reduce to the AdS case studied before once the value of the dynamical exponent is set to unity and the metric functions are accordingly chosen. The analytical results we present are general and can be applied to a variety of cases, in fact, to all spherically symmetric Lifshitz black hole solutions. We also implement the numerical analysis choosing some known Lifshitz black hole solutions as illustration. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1604.00495v1-abstract-full').style.display = 'none'; document.getElementById('1604.00495v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 2 April, 2016; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> April 2016. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Phys. Rev. D 93, 124073 (2016) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1603.07359">arXiv:1603.07359</a> <span> [<a href="https://arxiv.org/pdf/1603.07359">pdf</a>, <a href="https://arxiv.org/ps/1603.07359">ps</a>, <a href="https://arxiv.org/format/1603.07359">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="General Relativity and Quantum Cosmology">gr-qc</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="High Energy Physics - Theory">hep-th</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1103/PhysRevD.93.124012">10.1103/PhysRevD.93.124012 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Regular black holes: Guilfoyle's electrically charged solutions with a perfect fluid phantom core </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/gr-qc?searchtype=author&query=Lemos%2C+J+P+S">Jos茅 P. S. Lemos</a>, <a href="/search/gr-qc?searchtype=author&query=Zanchin%2C+V+T">Vilson T. Zanchin</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1603.07359v2-abstract-short" style="display: inline;"> Regular black hole solutions are found among the Guilfoyle exact solutions. These are spherically symmetric solutions of general relativity coupled to Maxwell's electromagnetism and charged matter where the metric potentials and electromagnetic fields are related in some particularly simple form. We show that, for certain ranges of the parameters, there are objects which correspond to regular char… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1603.07359v2-abstract-full').style.display = 'inline'; document.getElementById('1603.07359v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1603.07359v2-abstract-full" style="display: none;"> Regular black hole solutions are found among the Guilfoyle exact solutions. These are spherically symmetric solutions of general relativity coupled to Maxwell's electromagnetism and charged matter where the metric potentials and electromagnetic fields are related in some particularly simple form. We show that, for certain ranges of the parameters, there are objects which correspond to regular charged black holes, whose interior region is filled by an electrically charged phantom-like fluid, or, in the limiting case, a de Sitter false vacuum fluid, and whose exterior region is Reissner-Nordstr枚m. The boundary between both regions is a smooth boundary surface, except in the limiting case where the boundary is made of a massless electrically charged spherically symmetric coat. The main physical and geometrical properties of such charged regular solutions are analyzed. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1603.07359v2-abstract-full').style.display = 'none'; document.getElementById('1603.07359v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 28 June, 2016; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 23 March, 2016; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> March 2016. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Phys. Rev. D 93, 124012 (2016) </p> </li> </ol> <nav class="pagination is-small is-centered breathe-horizontal" role="navigation" aria-label="pagination"> <a href="" class="pagination-previous is-invisible">Previous </a> <a href="/search/?searchtype=author&query=Lemos%2C+J+P+S&start=50" class="pagination-next" >Next </a> <ul class="pagination-list"> <li> <a href="/search/?searchtype=author&query=Lemos%2C+J+P+S&start=0" class="pagination-link is-current" aria-label="Goto page 1">1 </a> </li> <li> <a href="/search/?searchtype=author&query=Lemos%2C+J+P+S&start=50" class="pagination-link " aria-label="Page 2" aria-current="page">2 </a> </li> <li> <a href="/search/?searchtype=author&query=Lemos%2C+J+P+S&start=100" class="pagination-link " aria-label="Page 3" aria-current="page">3 </a> </li> <li> <a href="/search/?searchtype=author&query=Lemos%2C+J+P+S&start=150" class="pagination-link " aria-label="Page 4" aria-current="page">4 </a> </li> </ul> </nav> <div class="is-hidden-tablet">  <span class="help" 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