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breathe-horizontal" role="navigation" aria-label="pagination"> <a href="" class="pagination-previous is-invisible">Previous </a> <a href="/search/?searchtype=author&query=Giri%2C+S+K&start=50" class="pagination-next" >Next </a> <ul class="pagination-list"> <li> <a href="/search/?searchtype=author&query=Giri%2C+S+K&start=0" class="pagination-link is-current" aria-label="Goto page 1">1 </a> </li> <li> <a href="/search/?searchtype=author&query=Giri%2C+S+K&start=50" class="pagination-link " aria-label="Page 2" aria-current="page">2 </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/2410.11620">arXiv:2410.11620</a> <span> [<a href="https://arxiv.org/pdf/2410.11620">pdf</a>, <a href="https://arxiv.org/format/2410.11620">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link 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="Astrophysics of Galaxies">astro-ph.GA</span> </div> </div> <p class="title is-5 mathjax"> Exploring the effect of different cosmologies on the Epoch of Reionization 21-cm signal with POLAR </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Acharya%2C+A">Anshuman Acharya</a>, <a href="/search/?searchtype=author&query=Ma%2C+Q">Qing-bo Ma</a>, <a href="/search/?searchtype=author&query=Giri%2C+S+K">Sambit K. Giri</a>, <a href="/search/?searchtype=author&query=Ciardi%2C+B">Benedetta Ciardi</a>, <a href="/search/?searchtype=author&query=Ghara%2C+R">Raghunath Ghara</a>, <a href="/search/?searchtype=author&query=Mellema%2C+G">Garrelt Mellema</a>, <a href="/search/?searchtype=author&query=Zaroubi%2C+S">Saleem Zaroubi</a>, <a href="/search/?searchtype=author&query=Hothi%2C+I">Ian Hothi</a>, <a href="/search/?searchtype=author&query=Iliev%2C+I+T">Ilian T. Iliev</a>, <a href="/search/?searchtype=author&query=Koopmans%2C+L+V+E">L茅on V. E. Koopmans</a>, <a href="/search/?searchtype=author&query=Bianco%2C+M">Michele Bianco</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="2410.11620v1-abstract-short" style="display: inline;"> A detection of the 21-cm signal power spectrum from the Epoch of Reionization is imminent, thanks to consistent advancements from telescopes such as LOFAR, MWA, and HERA, along with the development of SKA. In light of this progress, it is crucial to expand the parameter space of simulations used to infer astrophysical properties from this signal. In this work, we explore the role of cosmological p… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2410.11620v1-abstract-full').style.display = 'inline'; document.getElementById('2410.11620v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2410.11620v1-abstract-full" style="display: none;"> A detection of the 21-cm signal power spectrum from the Epoch of Reionization is imminent, thanks to consistent advancements from telescopes such as LOFAR, MWA, and HERA, along with the development of SKA. In light of this progress, it is crucial to expand the parameter space of simulations used to infer astrophysical properties from this signal. In this work, we explore the role of cosmological parameters such as the Hubble constant $H_0$ and the matter clustering amplitude $蟽_8$, whose values as provided by measurements at different redshifts are in tension. We run $N$-body simulations using GADGET-4, and post-process them with the reionization simulation code POLAR, that uses L-GALAXIES to include galaxy formation and evolution properties and GRIZZLY to execute 1-D radiative transfer of ionizing photons in the intergalactic medium (IGM). We compare our results with the latest JWST observations and explore which astrophysical properties for different cosmologies are necessary to match the observed UV luminosity functions at redshifts $z = 10$ and 9. Additionally, we explore the impact of these parameters on the observed 21-cm signal power spectrum, focusing on the redshifts within the range of LOFAR 21-cm signal observations ($z \approx 8.5-10$). Despite differences in cosmological and astrophysical parameters, the 21-cm power spectrum at these redshifts agrees with presently observed upper limits. This suggests the need for broader physical parameter spaces for inference modeling to account for all models that agree with observations. However, we also propose stronger constraining power by using a combination of galactic and IGM observables. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2410.11620v1-abstract-full').style.display = 'none'; document.getElementById('2410.11620v1-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 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">16 pages, 8 figures, 2 tables. Submitted to the Monthly Notices of the Royal Astronomical Society (MNRAS)</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Report number:</span> NORDITA-2024-035 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2409.19288">arXiv:2409.19288</a> <span> [<a href="https://arxiv.org/pdf/2409.19288">pdf</a>, <a href="https://arxiv.org/format/2409.19288">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Astrophysics of Galaxies">astro-ph.GA</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="Atomic Physics">physics.atom-ph</span> </div> </div> <p class="title is-5 mathjax"> Lyman-$伪$ feedback prevails at Cosmic Dawn: Implications for the first galaxies, stars, and star clusters </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Nebrin%2C+O">Olof Nebrin</a>, <a href="/search/?searchtype=author&query=Smith%2C+A">Aaron Smith</a>, <a href="/search/?searchtype=author&query=Lorinc%2C+K">Kevin Lorinc</a>, <a href="/search/?searchtype=author&query=H%C3%B6rnquist%2C+J">Johan H枚rnquist</a>, <a href="/search/?searchtype=author&query=Larson%2C+%C3%85">脜sa Larson</a>, <a href="/search/?searchtype=author&query=Mellema%2C+G">Garrelt Mellema</a>, <a href="/search/?searchtype=author&query=Giri%2C+S+K">Sambit K. Giri</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="2409.19288v1-abstract-short" style="display: inline;"> Radiation pressure from Lyman-$伪$ (Ly$伪$) scattering is a potentially dominant form of early stellar feedback, capable of injecting up to $\sim 100 \, \times$ more momentum into the interstellar medium (ISM) than UV continuum radiation pressure and stellar winds. Ly$伪$ feedback is particularly strong in dust-poor environments and is thus especially important during the formation of the first stars… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2409.19288v1-abstract-full').style.display = 'inline'; document.getElementById('2409.19288v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2409.19288v1-abstract-full" style="display: none;"> Radiation pressure from Lyman-$伪$ (Ly$伪$) scattering is a potentially dominant form of early stellar feedback, capable of injecting up to $\sim 100 \, \times$ more momentum into the interstellar medium (ISM) than UV continuum radiation pressure and stellar winds. Ly$伪$ feedback is particularly strong in dust-poor environments and is thus especially important during the formation of the first stars and galaxies. As upcoming galaxy formation simulations incorporate Ly$伪$ feedback, it is crucial to consider processes that can limit it to avoid placing $螞$CDM in apparent tension with recent \textit{JWST} observations indicating efficient star formation at Cosmic Dawn. We study Ly$伪$ feedback using a novel analytical Ly$伪$ radiative transfer solution that includes the effects of continuum absorption, gas velocity gradients, Ly$伪$ destruction (e.g. by $2p \rightarrow 2s$ transitions), ISM turbulence, and atomic recoil. We verify our solution for uniform clouds using extensive Monte Carlo radiative transfer (MCRT) tests, and resolve a previous discrepancy between analytical and MCRT predictions. We then study the sensitivity of Ly$伪$ feedback to the aforementioned effects. While these can dampen Ly$伪$ feedback by a factor $\lesssim \textrm{few} \times 10$, we find it remains $\gtrsim 5 - 100 \, \times$ stronger than direct radiation pressure and therefore cannot be neglected. We provide an accurate fit for the Ly$伪$ force multiplier $M_{\rm F}$, suitable for implementation in subgrid models for galaxy formation simulations. Our findings highlight the critical role of Ly$伪$ feedback in regulating star formation at Cosmic Dawn, and underscore the necessity of incorporating it into simulations to accurately model early galaxy evolution. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2409.19288v1-abstract-full').style.display = 'none'; document.getElementById('2409.19288v1-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 September, 2024; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> September 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">Comments welcome! 42 pages (31 pages main text, the rest an extensive Appendix + references), 20 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/2409.11368">arXiv:2409.11368</a> <span> [<a href="https://arxiv.org/pdf/2409.11368">pdf</a>, <a href="https://arxiv.org/format/2409.11368">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Chemical Physics">physics.chem-ph</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Quantum Physics">quant-ph</span> </div> </div> <p class="title is-5 mathjax"> Manipulating Two-Photon Absorption of Molecules through Efficient Optimization of Entangled Light </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Giri%2C+S+K">Sajal Kumar Giri</a>, <a href="/search/?searchtype=author&query=Schatz%2C+G+C">George C. Schatz</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="2409.11368v1-abstract-short" style="display: inline;"> We report how the unique temporal and spectral features of pulsed entangled photons from a parametric downconversion source can be utilized for manipulating electronic excitations through the optimization of their spectral phase. A new comprehensive optimization protocol based on Bayesian optimization has been developed in this work to selectively excite electronic states accessible by two-photon… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2409.11368v1-abstract-full').style.display = 'inline'; document.getElementById('2409.11368v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2409.11368v1-abstract-full" style="display: none;"> We report how the unique temporal and spectral features of pulsed entangled photons from a parametric downconversion source can be utilized for manipulating electronic excitations through the optimization of their spectral phase. A new comprehensive optimization protocol based on Bayesian optimization has been developed in this work to selectively excite electronic states accessible by two-photon absorption. Using our optimization method, the entangled two-photon absorption probability for a thiophene dendrimer can be enhanced by up to a factor of 20 while classical light turns out to be nonoptimizable. Moreover, the optimization involving photon entanglement enables selective excitation that would not be possible otherwise. In addition to optimization, we have explored entangled two-photon absorption in the small entanglement time limit showing that entangled light can excite molecular electronic states that are vanishingly small for classical light. We demonstrate these opportunities with an application to a thiophene dendrimer. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2409.11368v1-abstract-full').style.display = 'none'; document.getElementById('2409.11368v1-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 September, 2024; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> September 2024. </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2408.16814">arXiv:2408.16814</a> <span> [<a href="https://arxiv.org/pdf/2408.16814">pdf</a>, <a href="https://arxiv.org/format/2408.16814">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Cosmology and Nongalactic Astrophysics">astro-ph.CO</span> </div> </div> <p class="title is-5 mathjax"> Deep learning approach for identification of HII regions during reionization in 21-cm observations -- III. image recovery </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Bianco%2C+M">Michele Bianco</a>, <a href="/search/?searchtype=author&query=Giri%2C+S+K">Sambit. K. Giri</a>, <a href="/search/?searchtype=author&query=Sharma%2C+R">Rohit Sharma</a>, <a href="/search/?searchtype=author&query=Chen%2C+T">Tianyue Chen</a>, <a href="/search/?searchtype=author&query=Krishna%2C+S+P">Shreyam Parth Krishna</a>, <a href="/search/?searchtype=author&query=Finlay%2C+C">Chris Finlay</a>, <a href="/search/?searchtype=author&query=Nistane%2C+V">Viraj Nistane</a>, <a href="/search/?searchtype=author&query=Denzel%2C+P">Philipp Denzel</a>, <a href="/search/?searchtype=author&query=De+Santis%2C+M">Massimo De Santis</a>, <a href="/search/?searchtype=author&query=Ghorbel%2C+H">Hatem Ghorbel</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="2408.16814v1-abstract-short" style="display: inline;"> The low-frequency component of the upcoming Square Kilometre Array Observatory (SKA-Low) will be sensitive enough to construct 3D tomographic images of the 21-cm signal distribution during reionization. However, foreground contamination poses challenges for detecting this signal, and image recovery will heavily rely on effective mitigation methods. We introduce \texttt{SERENEt}, a deep-learning fr… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2408.16814v1-abstract-full').style.display = 'inline'; document.getElementById('2408.16814v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2408.16814v1-abstract-full" style="display: none;"> The low-frequency component of the upcoming Square Kilometre Array Observatory (SKA-Low) will be sensitive enough to construct 3D tomographic images of the 21-cm signal distribution during reionization. However, foreground contamination poses challenges for detecting this signal, and image recovery will heavily rely on effective mitigation methods. We introduce \texttt{SERENEt}, a deep-learning framework designed to recover the 21-cm signal from SKA-Low's foreground-contaminated observations, enabling the detection of ionized (HII) and neutral (HI) regions during reionization. \texttt{SERENEt} can recover the signal distribution with an average accuracy of 75 per cent at the early stages ($\overline{x}_\mathrm{HI}\simeq0.9$) and up to 90 per cent at the late stages of reionization ($\overline{x}_\mathrm{HI}\simeq0.1$). Conversely, HI region detection starts at 92 per cent accuracy, decreasing to 73 per cent as reionization progresses. Beyond improving image recovery, \texttt{SERENEt} provides cylindrical power spectra with an average accuracy exceeding 93 per cent throughout the reionization period. We tested \texttt{SERENEt} on a 10-degree field-of-view simulation, consistently achieving better and more stable results when prior maps were provided. Notably, including prior information about HII region locations improved 21-cm signal recovery by approximately 10 per cent. This capability was demonstrated by supplying \texttt{SERENEt} with ionizing source distribution measurements, showing that high-redshift galaxy surveys of similar observation fields can optimize foreground mitigation and enhance 21-cm image construction. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2408.16814v1-abstract-full').style.display = 'none'; document.getElementById('2408.16814v1-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 August, 2024; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> August 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, 14 figures, 1 table</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2407.03523">arXiv:2407.03523</a> <span> [<a href="https://arxiv.org/pdf/2407.03523">pdf</a>, <a href="https://arxiv.org/format/2407.03523">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Cosmology and Nongalactic Astrophysics">astro-ph.CO</span> </div> </div> <p class="title is-5 mathjax"> Inferring IGM parameters from the redshifted 21-cm Power Spectrum using Artificial Neural Networks </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Choudhury%2C+M">Madhurima Choudhury</a>, <a href="/search/?searchtype=author&query=Ghara%2C+R">Raghunath Ghara</a>, <a href="/search/?searchtype=author&query=Zaroubi%2C+S">Saleem Zaroubi</a>, <a href="/search/?searchtype=author&query=Ciardi%2C+B">Benedetta Ciardi</a>, <a href="/search/?searchtype=author&query=Koopmans%2C+L+V+E">Leon V. E. Koopmans</a>, <a href="/search/?searchtype=author&query=Mellema%2C+G">Garrelt Mellema</a>, <a href="/search/?searchtype=author&query=Shaw%2C+A+K">Abinash Kumar Shaw</a>, <a href="/search/?searchtype=author&query=Acharya%2C+A">Anshuman Acharya</a>, <a href="/search/?searchtype=author&query=Iliev%2C+I+T">I. T. Iliev</a>, <a href="/search/?searchtype=author&query=Ma%2C+Q">Qing-Bo Ma</a>, <a href="/search/?searchtype=author&query=Giri%2C+S+K">Sambit K. Giri</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="2407.03523v1-abstract-short" style="display: inline;"> The high redshift 21-cm signal promises to be a crucial probe of the state of the intergalactic medium (IGM). Understanding the connection between the observed 21-cm power spectrum and the physical quantities intricately associated with the IGM is crucial to fully understand the evolution of our Universe. In this study, we develop an emulator using artificial neural network (ANN) to predict the 21… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2407.03523v1-abstract-full').style.display = 'inline'; document.getElementById('2407.03523v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2407.03523v1-abstract-full" style="display: none;"> The high redshift 21-cm signal promises to be a crucial probe of the state of the intergalactic medium (IGM). Understanding the connection between the observed 21-cm power spectrum and the physical quantities intricately associated with the IGM is crucial to fully understand the evolution of our Universe. In this study, we develop an emulator using artificial neural network (ANN) to predict the 21-cm power spectrum from a given set of IGM properties, namely, the bubble size distribution and the volume averaged ionization fraction. This emulator is implemented within a standard Bayesian framework to constrain the IGM parameters from a given 21-cm power spectrum. We compare the performance of the Bayesian method to an alternate method using ANN to predict the IGM parameters from a given input power spectrum, and find that both methods yield similar levels of accuracy, while the ANN is significantly faster. We also use this ANN method of parameter estimation to predict the IGM parameters from a test set contaminated with noise levels expected from the SKA-LOW instrument after 1000 hours of observation. Finally, we train a separate ANN to predict the source parameters from the IGM parameters directly, at a redshift of $z=9.1$, demonstrating the possibility of a non-analytic inference of the source parameters from the IGM parameters for the first time. We achieve high accuracies, with R2-scores ranging between $0.898-0.978$ for the ANN emulator and between $0.966-0.986$ and $0.817-0.981$ for the predictions of IGM parameters from 21-cm power spectrum and source parameters from IGM parameters, respectively. The predictions of the IGM parameters from the Bayesian method incorporating the ANN emulator leads to tight constraints with error bars around $\pm{0.14}$ on the IGM parameters. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2407.03523v1-abstract-full').style.display = 'none'; document.getElementById('2407.03523v1-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> 3 July, 2024; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> July 2024. </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2406.18274">arXiv:2406.18274</a> <span> [<a href="https://arxiv.org/pdf/2406.18274">pdf</a>, <a href="https://arxiv.org/format/2406.18274">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Cosmology and Nongalactic Astrophysics">astro-ph.CO</span> </div> </div> <p class="title is-5 mathjax"> Euclid preparation. Sensitivity to non-standard particle dark matter model </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Euclid+Collaboration"> Euclid Collaboration</a>, <a href="/search/?searchtype=author&query=Lesgourgues%2C+J">J. Lesgourgues</a>, <a href="/search/?searchtype=author&query=Schwagereit%2C+J">J. Schwagereit</a>, <a href="/search/?searchtype=author&query=Bucko%2C+J">J. Bucko</a>, <a href="/search/?searchtype=author&query=Parimbelli%2C+G">G. Parimbelli</a>, <a href="/search/?searchtype=author&query=Giri%2C+S+K">S. K. Giri</a>, <a href="/search/?searchtype=author&query=Hervas-Peters%2C+F">F. Hervas-Peters</a>, <a href="/search/?searchtype=author&query=Schneider%2C+A">A. Schneider</a>, <a href="/search/?searchtype=author&query=Archidiacono%2C+M">M. Archidiacono</a>, <a href="/search/?searchtype=author&query=Pace%2C+F">F. Pace</a>, <a href="/search/?searchtype=author&query=Sakr%2C+Z">Z. Sakr</a>, <a href="/search/?searchtype=author&query=Amara%2C+A">A. Amara</a>, <a href="/search/?searchtype=author&query=Amendola%2C+L">L. Amendola</a>, <a href="/search/?searchtype=author&query=Andreon%2C+S">S. Andreon</a>, <a href="/search/?searchtype=author&query=Auricchio%2C+N">N. Auricchio</a>, <a href="/search/?searchtype=author&query=Aussel%2C+H">H. Aussel</a>, <a href="/search/?searchtype=author&query=Baccigalupi%2C+C">C. Baccigalupi</a>, <a href="/search/?searchtype=author&query=Baldi%2C+M">M. Baldi</a>, <a href="/search/?searchtype=author&query=Bardelli%2C+S">S. Bardelli</a>, <a href="/search/?searchtype=author&query=Bender%2C+R">R. Bender</a>, <a href="/search/?searchtype=author&query=Bodendorf%2C+C">C. Bodendorf</a>, <a href="/search/?searchtype=author&query=Bonino%2C+D">D. Bonino</a>, <a href="/search/?searchtype=author&query=Branchini%2C+E">E. Branchini</a>, <a href="/search/?searchtype=author&query=Brescia%2C+M">M. Brescia</a>, <a href="/search/?searchtype=author&query=Brinchmann%2C+J">J. Brinchmann</a> , et al. (227 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="2406.18274v1-abstract-short" style="display: inline;"> The Euclid mission of the European Space Agency will provide weak gravitational lensing and galaxy clustering surveys that can be used to constrain the standard cosmological model and its extensions, with an opportunity to test the properties of dark matter beyond the minimal cold dark matter paradigm. We present forecasts from the combination of these surveys on the parameters describing four int… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2406.18274v1-abstract-full').style.display = 'inline'; document.getElementById('2406.18274v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2406.18274v1-abstract-full" style="display: none;"> The Euclid mission of the European Space Agency will provide weak gravitational lensing and galaxy clustering surveys that can be used to constrain the standard cosmological model and its extensions, with an opportunity to test the properties of dark matter beyond the minimal cold dark matter paradigm. We present forecasts from the combination of these surveys on the parameters describing four interesting and representative non-minimal dark matter models: a mixture of cold and warm dark matter relics; unstable dark matter decaying either into massless or massive relics; and dark matter experiencing feeble interactions with relativistic relics. We model these scenarios at the level of the non-linear matter power spectrum using emulators trained on dedicated N-body simulations. We use a mock Euclid likelihood to fit mock data and infer error bars on dark matter parameters marginalised over other parameters. We find that the Euclid photometric probe (alone or in combination with CMB data from the Planck satellite) will be sensitive to the effect of each of the four dark matter models considered here. The improvement will be particularly spectacular for decaying and interacting dark matter models. With Euclid, the bounds on some dark matter parameters can improve by up to two orders of magnitude compared to current limits. We discuss the dependence of predicted uncertainties on different assumptions: inclusion of photometric galaxy clustering data, minimum angular scale taken into account, modelling of baryonic feedback effects. We conclude that the Euclid mission will be able to measure quantities related to the dark sector of particle physics with unprecedented sensitivity. This will provide important information for model building in high-energy physics. Any hint of a deviation from the minimal cold dark matter paradigm would have profound implications for cosmology and particle physics. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2406.18274v1-abstract-full').style.display = 'none'; document.getElementById('2406.18274v1-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 June, 2024; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> June 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">31 pages, 21 figures</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Report number:</span> TTK-24-26 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2405.13491">arXiv:2405.13491</a> <span> [<a href="https://arxiv.org/pdf/2405.13491">pdf</a>, <a href="https://arxiv.org/format/2405.13491">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link 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="Astrophysics of Galaxies">astro-ph.GA</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Instrumentation and Methods for Astrophysics">astro-ph.IM</span> </div> </div> <p class="title is-5 mathjax"> Euclid. I. Overview of the Euclid mission </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Euclid+Collaboration"> Euclid Collaboration</a>, <a href="/search/?searchtype=author&query=Mellier%2C+Y">Y. Mellier</a>, <a href="/search/?searchtype=author&query=Abdurro%27uf"> Abdurro'uf</a>, <a href="/search/?searchtype=author&query=Barroso%2C+J+A+A">J. A. Acevedo Barroso</a>, <a href="/search/?searchtype=author&query=Ach%C3%BAcarro%2C+A">A. Ach煤carro</a>, <a href="/search/?searchtype=author&query=Adamek%2C+J">J. Adamek</a>, <a href="/search/?searchtype=author&query=Adam%2C+R">R. Adam</a>, <a href="/search/?searchtype=author&query=Addison%2C+G+E">G. E. Addison</a>, <a href="/search/?searchtype=author&query=Aghanim%2C+N">N. Aghanim</a>, <a href="/search/?searchtype=author&query=Aguena%2C+M">M. Aguena</a>, <a href="/search/?searchtype=author&query=Ajani%2C+V">V. Ajani</a>, <a href="/search/?searchtype=author&query=Akrami%2C+Y">Y. Akrami</a>, <a href="/search/?searchtype=author&query=Al-Bahlawan%2C+A">A. Al-Bahlawan</a>, <a href="/search/?searchtype=author&query=Alavi%2C+A">A. Alavi</a>, <a href="/search/?searchtype=author&query=Albuquerque%2C+I+S">I. S. Albuquerque</a>, <a href="/search/?searchtype=author&query=Alestas%2C+G">G. Alestas</a>, <a href="/search/?searchtype=author&query=Alguero%2C+G">G. Alguero</a>, <a href="/search/?searchtype=author&query=Allaoui%2C+A">A. Allaoui</a>, <a href="/search/?searchtype=author&query=Allen%2C+S+W">S. W. Allen</a>, <a href="/search/?searchtype=author&query=Allevato%2C+V">V. Allevato</a>, <a href="/search/?searchtype=author&query=Alonso-Tetilla%2C+A+V">A. V. Alonso-Tetilla</a>, <a href="/search/?searchtype=author&query=Altieri%2C+B">B. Altieri</a>, <a href="/search/?searchtype=author&query=Alvarez-Candal%2C+A">A. Alvarez-Candal</a>, <a href="/search/?searchtype=author&query=Alvi%2C+S">S. Alvi</a>, <a href="/search/?searchtype=author&query=Amara%2C+A">A. Amara</a> , et al. (1115 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="2405.13491v2-abstract-short" style="display: inline;"> The current standard model of cosmology successfully describes a variety of measurements, but the nature of its main ingredients, dark matter and dark energy, remains unknown. Euclid is a medium-class mission in the Cosmic Vision 2015-2025 programme of the European Space Agency (ESA) that will provide high-resolution optical imaging, as well as near-infrared imaging and spectroscopy, over about 14… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2405.13491v2-abstract-full').style.display = 'inline'; document.getElementById('2405.13491v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2405.13491v2-abstract-full" style="display: none;"> The current standard model of cosmology successfully describes a variety of measurements, but the nature of its main ingredients, dark matter and dark energy, remains unknown. Euclid is a medium-class mission in the Cosmic Vision 2015-2025 programme of the European Space Agency (ESA) that will provide high-resolution optical imaging, as well as near-infrared imaging and spectroscopy, over about 14,000 deg^2 of extragalactic sky. In addition to accurate weak lensing and clustering measurements that probe structure formation over half of the age of the Universe, its primary probes for cosmology, these exquisite data will enable a wide range of science. This paper provides a high-level overview of the mission, summarising the survey characteristics, the various data-processing steps, and data products. We also highlight the main science objectives and expected performance. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2405.13491v2-abstract-full').style.display = 'none'; document.getElementById('2405.13491v2-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 September, 2024; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 22 May, 2024; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> May 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">Accepted for publication in the A&A special issue`Euclid on Sky'</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2405.04273">arXiv:2405.04273</a> <span> [<a href="https://arxiv.org/pdf/2405.04273">pdf</a>, <a href="https://arxiv.org/format/2405.04273">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Cosmology and Nongalactic Astrophysics">astro-ph.CO</span> </div> </div> <p class="title is-5 mathjax"> The forest at EndEoR: The effect of Lyman Limit Systems on the End of Reionisation </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Georgiev%2C+I">Ivelin Georgiev</a>, <a href="/search/?searchtype=author&query=Mellema%2C+G">Garrelt Mellema</a>, <a href="/search/?searchtype=author&query=Giri%2C+S+K">Sambit K. Giri</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="2405.04273v1-abstract-short" style="display: inline;"> The final stages of cosmic reionisation (EndEoR) are expected to be strongly regulated by the residual neutral hydrogen in the already ionised regions of the Universe. Its presence limits the mean distance that ionising photons can travel and hence, the extent of the regions that sources of ionising photons can affect. The structures containing most of this residual neutral hydrogen are typically… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2405.04273v1-abstract-full').style.display = 'inline'; document.getElementById('2405.04273v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2405.04273v1-abstract-full" style="display: none;"> The final stages of cosmic reionisation (EndEoR) are expected to be strongly regulated by the residual neutral hydrogen in the already ionised regions of the Universe. Its presence limits the mean distance that ionising photons can travel and hence, the extent of the regions that sources of ionising photons can affect. The structures containing most of this residual neutral hydrogen are typically unresolved in large-scale simulations of reionisation. Here, we investigate and compare a range of approaches for including the effect of these small-scale absorbers, also known as Lyman limit systems (LLS), in such simulations. We evaluate the impact of these different approaches on the reionisation history, the evolution of the ultraviolet background, and its fluctuations. We also compare to observational results on the distribution of Lyman-$伪$ opacity towards the EndEoR and the measured mean free path of ionising photons. We further consider their effect on the 21-cm power spectrum. We find that although each of the different approaches can match some of the observed probes of the final stages of reionisation, only the use of a redshift-dependent and position-dependent LLS model is able to reproduce all of them. We therefore recommend that large-scale reionisation simulations, which aim to describe both the state of the ionised and neutral intergalactic medium use such an approach, although the other, simpler approaches are applicable depending on the science goal of the simulation. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2405.04273v1-abstract-full').style.display = 'none'; document.getElementById('2405.04273v1-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 May, 2024; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> May 2024. </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2405.00913">arXiv:2405.00913</a> <span> [<a href="https://arxiv.org/pdf/2405.00913">pdf</a>, <a href="https://arxiv.org/format/2405.00913">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Optics">physics.optics</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Classical Physics">physics.class-ph</span> </div> </div> <p class="title is-5 mathjax"> Laser Pulse Induced Second- and Third-Harmonic Generation of Gold Nanorods with Real-Time Time-Dependent Density Functional Tight Binding (RT-TDDFTB) Method </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Giri%2C+S+K">Sajal Kumar Giri</a>, <a href="/search/?searchtype=author&query=Schatz%2C+G+C">George C. Schatz</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="2405.00913v2-abstract-short" style="display: inline;"> In this study, we investigate second- and third-harmonic generation processes in Au nanorod systems using the real-time time-dependent density functional tight binding method. Our study focuses on the computation of nonlinear signals based on the time dependent dipole response induced by linearly polarized laser pulses interacting with nanoparticles. We systematically explore the influence of vari… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2405.00913v2-abstract-full').style.display = 'inline'; document.getElementById('2405.00913v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2405.00913v2-abstract-full" style="display: none;"> In this study, we investigate second- and third-harmonic generation processes in Au nanorod systems using the real-time time-dependent density functional tight binding method. Our study focuses on the computation of nonlinear signals based on the time dependent dipole response induced by linearly polarized laser pulses interacting with nanoparticles. We systematically explore the influence of various laser parameters, including pump intensity, duration, frequency, and polarization directions, on harmonic generation. We demonstrate all the results using Au nanorod dimer systems arranged in end-to-end configurations, and disrupting the spatial symmetry of regular single nanorod systems is crucial for second-harmonic generation processes. Furthermore, we study the impact of nanorod lengths, which lead to variable plasmon energies, on harmonic generation, and estimates of polarizabilities and hyper-polarizabilities are provided. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2405.00913v2-abstract-full').style.display = 'none'; document.getElementById('2405.00913v2-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, 2024; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 1 May, 2024; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> May 2024. </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2404.11686">arXiv:2404.11686</a> <span> [<a href="https://arxiv.org/pdf/2404.11686">pdf</a>, <a href="https://arxiv.org/format/2404.11686">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Cosmology and Nongalactic Astrophysics">astro-ph.CO</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/10.1051/0004-6361/202449444">10.1051/0004-6361/202449444 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Probing the intergalactic medium during the Epoch of Reionization using 21-cm signal power spectra </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Ghara%2C+R">Raghunath Ghara</a>, <a href="/search/?searchtype=author&query=Shaw%2C+A+K">Abinash Kumar Shaw</a>, <a href="/search/?searchtype=author&query=Zaroubi%2C+S">Saleem Zaroubi</a>, <a href="/search/?searchtype=author&query=Ciardi%2C+B">Benedetta Ciardi</a>, <a href="/search/?searchtype=author&query=Mellema%2C+G">Garrelt Mellema</a>, <a href="/search/?searchtype=author&query=Koopmans%2C+L+V+E">L茅on V. E. Koopmans</a>, <a href="/search/?searchtype=author&query=Acharya%2C+A">Anshuman Acharya</a>, <a href="/search/?searchtype=author&query=Choudhury%2C+M">Madhurima Choudhury</a>, <a href="/search/?searchtype=author&query=Giri%2C+S+K">Sambit K. Giri</a>, <a href="/search/?searchtype=author&query=Iliev%2C+I+T">Ilian T. Iliev</a>, <a href="/search/?searchtype=author&query=Ma%2C+Q">Qing-Bo Ma</a>, <a href="/search/?searchtype=author&query=Mertens%2C+F">Florent Mertens</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="2404.11686v1-abstract-short" style="display: inline;"> The redshifted 21-cm signal from the epoch of reionization (EoR) directly probes the ionization and thermal states of the intergalactic medium during that period. In particular, the distribution of the ionized regions around the radiating sources during EoR introduces scale-dependent features in the spherically-averaged EoR 21-cm signal power spectrum. The goal is to study these scale-dependent fe… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2404.11686v1-abstract-full').style.display = 'inline'; document.getElementById('2404.11686v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2404.11686v1-abstract-full" style="display: none;"> The redshifted 21-cm signal from the epoch of reionization (EoR) directly probes the ionization and thermal states of the intergalactic medium during that period. In particular, the distribution of the ionized regions around the radiating sources during EoR introduces scale-dependent features in the spherically-averaged EoR 21-cm signal power spectrum. The goal is to study these scale-dependent features at different stages of reionization using numerical simulations and build a source model-independent framework to probe the properties of the intergalactic medium using EoR 21-cm signal power spectrum measurements. Under the assumption of high spin temperature, we modelled the redshift evolution of the ratio of EoR 21-cm brightness temperature power spectrum and the corresponding density power spectrum using an ansatz consisting of a set of redshift and scale-independent parameters. This set of eight parameters probes the redshift evolution of the average ionization fraction and the quantities related to the morphology of the ionized regions. We have tested this ansatz on different reionization scenarios generated using different simulation algorithms and found that it is able to recover the redshift evolution of the average neutral fraction within an absolute deviation $\lesssim 0.1$. Our framework allows us to interpret 21-cm signal power spectra in terms of parameters related to the state of the IGM. This source model-independent framework can efficiently constrain reionization scenarios using multi-redshift power spectrum measurements with ongoing and future radio telescopes such as LOFAR, MWA, HERA, and SKA. This will add independent information regarding the EoR IGM properties. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2404.11686v1-abstract-full').style.display = 'none'; document.getElementById('2404.11686v1-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 April, 2024; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> April 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, 13 figures, 2 tables, Accepted for publication in Astronomy and Astrophysics</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Report number:</span> NORDITA 2024-009 </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> A&A 687, A252 (2024) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2404.08042">arXiv:2404.08042</a> <span> [<a href="https://arxiv.org/pdf/2404.08042">pdf</a>, <a href="https://arxiv.org/format/2404.08042">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Cosmology and Nongalactic Astrophysics">astro-ph.CO</span> </div> </div> <p class="title is-5 mathjax"> Testing common approximations to predict the 21cm signal at the Epoch of Reionization and Cosmic Dawn </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Schaeffer%2C+T">Timoth茅e Schaeffer</a>, <a href="/search/?searchtype=author&query=Giri%2C+S+K">Sambit K. Giri</a>, <a href="/search/?searchtype=author&query=Schneider%2C+A">Aurel Schneider</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="2404.08042v3-abstract-short" style="display: inline;"> Predicting the 21cm signal from the epoch of reionization and cosmic dawn is a complex and challenging task. Various simplifying assumptions have been applied over the last decades to make the modeling more affordable. In this paper, we investigate the validity of several such assumptions, using a simulation suite consisting of three different astrophysical source models that agree with the curren… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2404.08042v3-abstract-full').style.display = 'inline'; document.getElementById('2404.08042v3-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2404.08042v3-abstract-full" style="display: none;"> Predicting the 21cm signal from the epoch of reionization and cosmic dawn is a complex and challenging task. Various simplifying assumptions have been applied over the last decades to make the modeling more affordable. In this paper, we investigate the validity of several such assumptions, using a simulation suite consisting of three different astrophysical source models that agree with the current constraints on the reionization history and the UV luminosity function. We first show that the common assumption of a saturated spin temperature may lead to significant errors in the 21cm clustering signal over the full reionization period. The same is true for the assumption of a neutral universe during the cosmic dawn which may lead to significant deviation from the correct signal during the heating and the Lyman-$伪$ coupling period. Another popular simplifying assumption consists of predicting the global differential brightness temperature ($dT_b$) based on the average quantities of the reionization fraction, gas temperature, and Lyman-$伪$ coupling. We show that such an approach leads to a 10 percent deeper absorption signal compared to the results obtained by averaging the final $dT_b$-map. Finally, we investigate the simplifying method of breaking the 21cm clustering signal into different auto and cross components that are then solved assuming linearity. We show that even though the individual fields have a variance well below unity, they often cannot be treated perturbatively as the perturbations are strongly non-Gaussian. As a consequence, predictions based on the perturbative solution of individual auto and cross power spectra may lead to strongly biased results, even if higher-order terms are taken into account. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2404.08042v3-abstract-full').style.display = 'none'; document.getElementById('2404.08042v3-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 July, 2024; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 11 April, 2024; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> April 2024. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Report number:</span> NORDITA 2024-004 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2403.04838">arXiv:2403.04838</a> <span> [<a href="https://arxiv.org/pdf/2403.04838">pdf</a>, <a href="https://arxiv.org/format/2403.04838">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link 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="Astrophysics of Galaxies">astro-ph.GA</span> </div> </div> <p class="title is-5 mathjax"> The 21-cm signal during the end stages of reionization </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Giri%2C+S+K">Sambit K. Giri</a>, <a href="/search/?searchtype=author&query=Bianco%2C+M">Michele Bianco</a>, <a href="/search/?searchtype=author&query=Schaeffer%2C+T">Timoth茅e Schaeffer</a>, <a href="/search/?searchtype=author&query=Iliev%2C+I+T">Ilian T. Iliev</a>, <a href="/search/?searchtype=author&query=Mellema%2C+G">Garrelt Mellema</a>, <a href="/search/?searchtype=author&query=Schneider%2C+A">Aurel Schneider</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="2403.04838v2-abstract-short" style="display: inline;"> During the epoch of reionization (EoR), the 21-cm signal allows direct observation of the neutral hydrogen (HI) in the intergalactic medium (IGM). In the post-reionization era, this signal instead probes HI in galaxies, which traces the dark matter density distribution. With new numerical simulations, we investigated the end stages of reionization to elucidate the transition of our Universe into t… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2403.04838v2-abstract-full').style.display = 'inline'; document.getElementById('2403.04838v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2403.04838v2-abstract-full" style="display: none;"> During the epoch of reionization (EoR), the 21-cm signal allows direct observation of the neutral hydrogen (HI) in the intergalactic medium (IGM). In the post-reionization era, this signal instead probes HI in galaxies, which traces the dark matter density distribution. With new numerical simulations, we investigated the end stages of reionization to elucidate the transition of our Universe into the post-reionization era. Our models are consistent with the latest high-redshift measurements, including ultraviolet (UV) luminosity functions \RefereeReport{up to redshift $\simeq$8}. Notably, these models consistently reproduced the evolution of the UV photon background, which is constrained from Lyman-$伪$ absorption spectra. We studied the dependence of this background on the nature of photon sinks in the IGM, requiring mean free path of UV photons to be $\sim$10 comoving-megaparsecs (cMpc) during the EoR that increases gradually with time during late stages ($z\lesssim 6$). Our models revealed that the reionization of the IGM transitioned from an \textit{inside-out} to an \textit{outside-in} process when the Universe is less than 0.01 per cent neutral. During this epoch, the 21-cm signal also shifted from probing predominantly the HI in the IGM to that in galaxies. Furthermore, we identified a statistically significant number of large neutral islands (with sizes up to 40 cMpc) persisting until very late stages ($5 \lesssim z \lesssim 6$) that can imprint features in Lyman-$伪$ absorption spectra and also produce a knee-like feature in the 21-cm power spectrum. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2403.04838v2-abstract-full').style.display = 'none'; document.getElementById('2403.04838v2-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 August, 2024; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 7 March, 2024; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> March 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, 9 figures. Accepted for publication in MNRAS</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Report number:</span> NORDITA 2024-003 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2402.13478">arXiv:2402.13478</a> <span> [<a href="https://arxiv.org/pdf/2402.13478">pdf</a>, <a href="https://arxiv.org/format/2402.13478">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Chemical Physics">physics.chem-ph</span> </div> </div> <p class="title is-5 mathjax"> Plasmon Enhanced Spectroscopy and Photocatalysis </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Giri%2C+S+K">Sajal Kumar Giri</a>, <a href="/search/?searchtype=author&query=Schatz%2C+G+C">George C. Schatz</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="2402.13478v3-abstract-short" style="display: inline;"> This study examines the Raman scattering and charge transfer properties of molecules adsorbed on the surface of a tetrahedral Au$_{120}$ nanoparticle based on the time-dependent density functional tight-binding (TD-DFTB) method. We study Raman scattering (SERS) enhancements for pyridine where the molecule is adsorbed either on the tip (V complex) or surface (S complex) of the nanoparticle. The sca… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2402.13478v3-abstract-full').style.display = 'inline'; document.getElementById('2402.13478v3-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2402.13478v3-abstract-full" style="display: none;"> This study examines the Raman scattering and charge transfer properties of molecules adsorbed on the surface of a tetrahedral Au$_{120}$ nanoparticle based on the time-dependent density functional tight-binding (TD-DFTB) method. We study Raman scattering (SERS) enhancements for pyridine where the molecule is adsorbed either on the tip (V complex) or surface (S complex) of the nanoparticle. The scattering intensity is enhanced by a factor of 3-15 due to chemical effects while significantly larger enhancements (in the order of 10$^2$-10$^4$) are observed for plasmon resonance excitation at an energy of 2.5 eV depending on the adsorption site. Furthermore, we demonstrate charge transfer between the nanoparticle and a fullerene-based molecule after pulsed excitation of the plasmon resonance which shows how plasmon excitation can lead to negative molecular ion formation. All of these results are consistent with earlier studies using either TD-DFT theory or experimental measurements. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2402.13478v3-abstract-full').style.display = 'none'; document.getElementById('2402.13478v3-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 September, 2024; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 20 February, 2024; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> February 2024. </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2402.10932">arXiv:2402.10932</a> <span> [<a href="https://arxiv.org/pdf/2402.10932">pdf</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Materials Science">cond-mat.mtrl-sci</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Data Analysis, Statistics and Probability">physics.data-an</span> </div> </div> <p class="title is-5 mathjax"> Roadmap on Data-Centric Materials Science </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Bauer%2C+S">Stefan Bauer</a>, <a href="/search/?searchtype=author&query=Benner%2C+P">Peter Benner</a>, <a href="/search/?searchtype=author&query=Bereau%2C+T">Tristan Bereau</a>, <a href="/search/?searchtype=author&query=Blum%2C+V">Volker Blum</a>, <a href="/search/?searchtype=author&query=Boley%2C+M">Mario Boley</a>, <a href="/search/?searchtype=author&query=Carbogno%2C+C">Christian Carbogno</a>, <a href="/search/?searchtype=author&query=Catlow%2C+C+R+A">C. Richard A. Catlow</a>, <a href="/search/?searchtype=author&query=Dehm%2C+G">Gerhard Dehm</a>, <a href="/search/?searchtype=author&query=Eibl%2C+S">Sebastian Eibl</a>, <a href="/search/?searchtype=author&query=Ernstorfer%2C+R">Ralph Ernstorfer</a>, <a href="/search/?searchtype=author&query=Fekete%2C+%C3%81">脕d谩m Fekete</a>, <a href="/search/?searchtype=author&query=Foppa%2C+L">Lucas Foppa</a>, <a href="/search/?searchtype=author&query=Fratzl%2C+P">Peter Fratzl</a>, <a href="/search/?searchtype=author&query=Freysoldt%2C+C">Christoph Freysoldt</a>, <a href="/search/?searchtype=author&query=Gault%2C+B">Baptiste Gault</a>, <a href="/search/?searchtype=author&query=Ghiringhelli%2C+L+M">Luca M. Ghiringhelli</a>, <a href="/search/?searchtype=author&query=Giri%2C+S+K">Sajal K. Giri</a>, <a href="/search/?searchtype=author&query=Gladyshev%2C+A">Anton Gladyshev</a>, <a href="/search/?searchtype=author&query=Goyal%2C+P">Pawan Goyal</a>, <a href="/search/?searchtype=author&query=Hattrick-Simpers%2C+J">Jason Hattrick-Simpers</a>, <a href="/search/?searchtype=author&query=Kabalan%2C+L">Lara Kabalan</a>, <a href="/search/?searchtype=author&query=Karpov%2C+P">Petr Karpov</a>, <a href="/search/?searchtype=author&query=Khorrami%2C+M+S">Mohammad S. Khorrami</a>, <a href="/search/?searchtype=author&query=Koch%2C+C">Christoph Koch</a>, <a href="/search/?searchtype=author&query=Kokott%2C+S">Sebastian Kokott</a> , et al. (36 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="2402.10932v3-abstract-short" style="display: inline;"> Science is and always has been based on data, but the terms "data-centric" and the "4th paradigm of" materials research indicate a radical change in how information is retrieved, handled and research is performed. It signifies a transformative shift towards managing vast data collections, digital repositories, and innovative data analytics methods. The integration of Artificial Intelligence (AI) a… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2402.10932v3-abstract-full').style.display = 'inline'; document.getElementById('2402.10932v3-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2402.10932v3-abstract-full" style="display: none;"> Science is and always has been based on data, but the terms "data-centric" and the "4th paradigm of" materials research indicate a radical change in how information is retrieved, handled and research is performed. It signifies a transformative shift towards managing vast data collections, digital repositories, and innovative data analytics methods. The integration of Artificial Intelligence (AI) and its subset Machine Learning (ML), has become pivotal in addressing all these challenges. This Roadmap on Data-Centric Materials Science explores fundamental concepts and methodologies, illustrating diverse applications in electronic-structure theory, soft matter theory, microstructure research, and experimental techniques like photoemission, atom probe tomography, and electron microscopy. While the roadmap delves into specific areas within the broad interdisciplinary field of materials science, the provided examples elucidate key concepts applicable to a wider range of topics. The discussed instances offer insights into addressing the multifaceted challenges encountered in contemporary materials research. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2402.10932v3-abstract-full').style.display = 'none'; document.getElementById('2402.10932v3-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 May, 2024; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 1 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">Review, outlook, roadmap, perspective</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2402.03858">arXiv:2402.03858</a> <span> [<a href="https://arxiv.org/pdf/2402.03858">pdf</a>, <a href="https://arxiv.org/format/2402.03858">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Quantum Physics">quant-ph</span> </div> </div> <p class="title is-5 mathjax"> Higher-order nonclassicalities in hybrid coherent states </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Giri%2C+S+K">Sandip Kumar Giri</a>, <a href="/search/?searchtype=author&query=Sen%2C+B">Biswajit Sen</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="2402.03858v1-abstract-short" style="display: inline;"> In the development of quantum technologies, nonclassical states have been playing a pivotal role, as quantum advantage cannot be obtained without appropriate utilization of nonclassicality. In the present work, we consider a hybrid coherent state (HCS), which is a coherent superposition of the single-photon-added coherent (SPAC) state and a coherent state (CS). Here, we report higher-order nonclas… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2402.03858v1-abstract-full').style.display = 'inline'; document.getElementById('2402.03858v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2402.03858v1-abstract-full" style="display: none;"> In the development of quantum technologies, nonclassical states have been playing a pivotal role, as quantum advantage cannot be obtained without appropriate utilization of nonclassicality. In the present work, we consider a hybrid coherent state (HCS), which is a coherent superposition of the single-photon-added coherent (SPAC) state and a coherent state (CS). Here, we report higher-order nonclassical properties of HCS with a specific focus on higher-order squeezing and higher-order antibunching. It's shown that HCS is experimentally realizable, and this engineered quantum state can be used to produce quantum states with desired higher-order nonclassical properties. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2402.03858v1-abstract-full').style.display = 'none'; document.getElementById('2402.03858v1-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 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">7 pages, 4 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/2312.17636">arXiv:2312.17636</a> <span> [<a href="https://arxiv.org/pdf/2312.17636">pdf</a>, <a href="https://arxiv.org/format/2312.17636">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link 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> </div> </div> <p class="title is-5 mathjax"> Inverse Gertsenshtein effect as a probe of high-frequency gravitational waves </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=He%2C+Y">Yutong He</a>, <a href="/search/?searchtype=author&query=Giri%2C+S+K">Sambit K. Giri</a>, <a href="/search/?searchtype=author&query=Sharma%2C+R">Ramkishor Sharma</a>, <a href="/search/?searchtype=author&query=Mtchedlidze%2C+S">Salome Mtchedlidze</a>, <a href="/search/?searchtype=author&query=Georgiev%2C+I">Ivelin Georgiev</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="2312.17636v2-abstract-short" style="display: inline;"> We apply the inverse Gertsenshtein effect, i.e., the graviton-photon conversion in the presence of a magnetic field, to constrain high-frequency gravitational waves (HFGWs). Using existing astrophysical measurements, we compute upper limits on the GW energy densities $惟_{\rm GW}$ at 16 different frequency bands. Given the observed magnetisation of galaxy clusters with field strength… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2312.17636v2-abstract-full').style.display = 'inline'; document.getElementById('2312.17636v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2312.17636v2-abstract-full" style="display: none;"> We apply the inverse Gertsenshtein effect, i.e., the graviton-photon conversion in the presence of a magnetic field, to constrain high-frequency gravitational waves (HFGWs). Using existing astrophysical measurements, we compute upper limits on the GW energy densities $惟_{\rm GW}$ at 16 different frequency bands. Given the observed magnetisation of galaxy clusters with field strength $B\sim渭{\rm G}$ correlated on $\mathcal{O}(10)\,{\rm kpc}$ scales, we estimate HFGW constraints in the $\mathcal{O}(10^2)\,{\rm GHz}$ regime to be $惟_{\rm GW}\lesssim10^{16}$ with the temperature measurements of the Atacama Cosmology Telescope (ACT). Similarly, we conservatively obtain $惟_{\rm GW}\lesssim10^{13} (10^{11})$ in the $\mathcal{O}(10^2)\,{\rm MHz}$ ($\mathcal{O}(10)\,{\rm GHz}$) regime by assuming uniform magnetic field with strength $B\sim0.1\,{\rm nG}$ and saturating the excess signal over the Cosmic Microwave Background (CMB) reported by radio telescopes such as the Experiment to Detect the Global EoR Signature (EDGES), LOw Frequency ARray (LOFAR), and Murchison Widefield Array (MWA), and the balloon-borne second generation Absolute Radiometer for Cosmology, Astrophysics, and Diffuse Emission (ARCADE2) with graviton-induced photons. The upcoming Square Kilometer Array (SKA) can tighten these constraints by roughly 10 orders of magnitude, which will be a step closer to reaching the critical value of $惟_{\rm GW} = 1$ or the Big Bang Nucleosynthesis (BBN) bound of $惟_{\rm GW}\simeq1.2\times10^{-6}$. We point to future improvement of the SKA forecast and estimate that proposed CMB measurement at the level of $\mathcal{O}(10^{0-2})\,{\rm nK}$, such as Primordial Inflation Explorer (PIXIE) and Voyage 2050, are needed to viably detect stochastic backgrounds of HFGWs. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2312.17636v2-abstract-full').style.display = 'none'; document.getElementById('2312.17636v2-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 April, 2024; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 29 December, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> December 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">31 pages, 4 figures, 3 tables</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Report number:</span> NORDITA-2023-066 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2311.16633">arXiv:2311.16633</a> <span> [<a href="https://arxiv.org/pdf/2311.16633">pdf</a>, <a href="https://arxiv.org/format/2311.16633">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link 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="Instrumentation and Methods for Astrophysics">astro-ph.IM</span> </div> </div> <p class="title is-5 mathjax"> 21-cm Signal from the Epoch of Reionization: A Machine Learning upgrade to Foreground Removal with Gaussian Process Regression </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Acharya%2C+A">Anshuman Acharya</a>, <a href="/search/?searchtype=author&query=Mertens%2C+F">Florent Mertens</a>, <a href="/search/?searchtype=author&query=Ciardi%2C+B">Benedetta Ciardi</a>, <a href="/search/?searchtype=author&query=Ghara%2C+R">Raghunath Ghara</a>, <a href="/search/?searchtype=author&query=Koopmans%2C+L+V+E">L茅on V. E. Koopmans</a>, <a href="/search/?searchtype=author&query=Giri%2C+S+K">Sambit K. Giri</a>, <a href="/search/?searchtype=author&query=Hothi%2C+I">Ian Hothi</a>, <a href="/search/?searchtype=author&query=Ma%2C+Q">Qing-Bo Ma</a>, <a href="/search/?searchtype=author&query=Mellema%2C+G">Garrelt Mellema</a>, <a href="/search/?searchtype=author&query=Munshi%2C+S">Satyapan Munshi</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="2311.16633v2-abstract-short" style="display: inline;"> In recent years, a Gaussian Process Regression (GPR) based framework has been developed for foreground mitigation from data collected by the LOw-Frequency ARray (LOFAR), to measure the 21-cm signal power spectrum from the Epoch of Reionization (EoR) and Cosmic Dawn. However, it has been noted that through this method there can be a significant amount of signal loss if the EoR signal covariance is… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2311.16633v2-abstract-full').style.display = 'inline'; document.getElementById('2311.16633v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2311.16633v2-abstract-full" style="display: none;"> In recent years, a Gaussian Process Regression (GPR) based framework has been developed for foreground mitigation from data collected by the LOw-Frequency ARray (LOFAR), to measure the 21-cm signal power spectrum from the Epoch of Reionization (EoR) and Cosmic Dawn. However, it has been noted that through this method there can be a significant amount of signal loss if the EoR signal covariance is misestimated. To obtain better covariance models, we propose to use a kernel trained on the {\tt GRIZZLY} simulations using a Variational Auto-Encoder (VAE) based algorithm. In this work, we explore the abilities of this Machine Learning based kernel (VAE kernel) used with GPR, by testing it on mock signals from a variety of simulations, exploring noise levels corresponding to $\approx$10 nights ($\approx$141 hours) and $\approx$100 nights ($\approx$1410 hours) of observations with LOFAR. Our work suggests the possibility of successful extraction of the 21-cm signal within 2$蟽$ uncertainty in most cases using the VAE kernel, with better recovery of both shape and power than with previously used covariance models. We also explore the role of the excess noise component identified in past applications of GPR and additionally analyse the possibility of redshift dependence on the performance of the VAE kernel. The latter allows us to prepare for future LOFAR observations at a range of redshifts, as well as compare with results from other telescopes. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2311.16633v2-abstract-full').style.display = 'none'; document.getElementById('2311.16633v2-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 November, 2023; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 28 November, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> November 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">13 pages, 7 figures, 3 tables. Accepted for publication in the Monthly Notices of the Royal Astronomical Society</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Report number:</span> NORDITA 2023-074 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2311.01492">arXiv:2311.01492</a> <span> [<a href="https://arxiv.org/pdf/2311.01492">pdf</a>, <a href="https://arxiv.org/format/2311.01492">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Cosmology and Nongalactic Astrophysics">astro-ph.CO</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.ascom.2024.100861">10.1016/j.ascom.2024.100861 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> pyC$^2$Ray: A flexible and GPU-accelerated Radiative Transfer Framework for Simulating the Cosmic Epoch of Reionization </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Hirling%2C+P">Patrick Hirling</a>, <a href="/search/?searchtype=author&query=Bianco%2C+M">Michele Bianco</a>, <a href="/search/?searchtype=author&query=Giri%2C+S+K">Sambit K. Giri</a>, <a href="/search/?searchtype=author&query=Iliev%2C+I+T">Ilian T. Iliev</a>, <a href="/search/?searchtype=author&query=Mellema%2C+G">Garrelt Mellema</a>, <a href="/search/?searchtype=author&query=Kneib%2C+J">Jean-Paul Kneib</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="2311.01492v2-abstract-short" style="display: inline;"> Detailed modeling of the evolution of neutral hydrogen in the intergalactic medium during the Epoch of Reionization, $5 \leq z \leq 20$, is critical in interpreting the cosmological signals from current and upcoming 21-cm experiments such as the Low-Frequency Array (LOFAR) and the Square Kilometre Array (SKA). Numerical radiative transfer codes provide the most physically accurate models of the re… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2311.01492v2-abstract-full').style.display = 'inline'; document.getElementById('2311.01492v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2311.01492v2-abstract-full" style="display: none;"> Detailed modeling of the evolution of neutral hydrogen in the intergalactic medium during the Epoch of Reionization, $5 \leq z \leq 20$, is critical in interpreting the cosmological signals from current and upcoming 21-cm experiments such as the Low-Frequency Array (LOFAR) and the Square Kilometre Array (SKA). Numerical radiative transfer codes provide the most physically accurate models of the reionization process. However, they are computationally expensive as they must encompass enormous cosmological volumes while accurately capturing astrophysical processes occurring at small scales ($\lesssim\rm Mpc$). Here, we present pyC$^2$Ray, an updated version of the massively parallel ray-tracing and chemistry code, C$^2$Ray, which has been extensively employed in reionization simulations. The most time-consuming part of the code is calculating the hydrogen column density along the path of the ionizing photons. Here, we present the Accelerated Short-characteristics Octahedral ray-tracing (ASORA) method, a ray-tracing algorithm specifically designed to run on graphical processing units (GPUs). We include a modern Python interface, allowing easy and customized use of the code without compromising computational efficiency. We test pyC$^2$Ray on a series of standard ray-tracing tests and a complete cosmological simulation with volume size $(349\,\rm Mpc)^3$, mesh size of $250^3$ and approximately $10^6$ sources. Compared to the original code, pyC$^2$Ray achieves the same results with negligible fractional differences, $\sim 10^{-5}$, and a speedup factor of two orders of magnitude. Benchmark analysis shows that ASORA takes a few nanoseconds per source per voxel and scales linearly for an increasing number of sources and voxels within the ray-tracing radii. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2311.01492v2-abstract-full').style.display = 'none'; document.getElementById('2311.01492v2-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 July, 2024; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 2 November, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> November 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">20 pages, 13 figures, 1 table</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Report number:</span> NORDITA 2023-033 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2309.03865">arXiv:2309.03865</a> <span> [<a href="https://arxiv.org/pdf/2309.03865">pdf</a>, <a href="https://arxiv.org/format/2309.03865">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Cosmology and Nongalactic Astrophysics">astro-ph.CO</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/10.1051/0004-6361/202449195">10.1051/0004-6361/202449195 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Constraining Hot Dark Matter Sub-Species with Weak Lensing and the Cosmic Microwave Background Radiation </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Peters%2C+F+H">Fabian Hervas Peters</a>, <a href="/search/?searchtype=author&query=Schneider%2C+A">Aurel Schneider</a>, <a href="/search/?searchtype=author&query=Bucko%2C+J">Jozef Bucko</a>, <a href="/search/?searchtype=author&query=Giri%2C+S+K">Sambit K. Giri</a>, <a href="/search/?searchtype=author&query=Parimbelli%2C+G">Gabriele Parimbelli</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="2309.03865v1-abstract-short" style="display: inline;"> Although it is well known that the bulk of dark matter (DM) has to be cold, the existence of an additional sub-dominant, hot species remains a valid possibility. In this paper we investigate the potential of the cosmic shear power spectrum to constrain such a mixed (hot plus cold) DM scenario with two additional free parameters, the hot-to-total DM fraction ($f_{\rm hdm}$) and the thermal mass of… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2309.03865v1-abstract-full').style.display = 'inline'; document.getElementById('2309.03865v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2309.03865v1-abstract-full" style="display: none;"> Although it is well known that the bulk of dark matter (DM) has to be cold, the existence of an additional sub-dominant, hot species remains a valid possibility. In this paper we investigate the potential of the cosmic shear power spectrum to constrain such a mixed (hot plus cold) DM scenario with two additional free parameters, the hot-to-total DM fraction ($f_{\rm hdm}$) and the thermal mass of the hot component ($m_{\rm hdm}$). Running a Bayesian inference analysis for both the Kilo-Degree Survey cosmic shear data (KiDS) as well as the Cosmic Microwave Background (CMB) temperature and polarisation data from Planck, we derive new constraints for the mixed DM scenario. We find a 95 per cent confidence limit of $f_{\rm hdm}<0.08$ for a very hot species of $m_{\rm hdm}\leq20$ eV. This constraint is weakened to $f_{\rm hdm}<0.25$ for $m_{\rm hdm}\leq80$ eV. Scenarios with masses above $m_{\rm hdm}\sim200$ eV remain unconstrained by the data. Next to providing limits, we investigate the potential of mixed DM to address the clustering (or $S_8$) tension between lensing and the CMB. We find a reduction of the 2D ($惟_m - S_8$) tension from 2.9$蟽$ to 1.6$蟽$ when going from a pure cold DM to a mixed DM scenario. When computing the 1D gaussian tension on $S_8$ the improvement is milder, from 2.4$蟽$ to 2.0$蟽$. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2309.03865v1-abstract-full').style.display = 'none'; document.getElementById('2309.03865v1-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 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">8 pages, 4 figures</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Report number:</span> NORDITA 2023-032 </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> A&A 687, A161 (2024) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2307.03222">arXiv:2307.03222</a> <span> [<a href="https://arxiv.org/pdf/2307.03222">pdf</a>, <a href="https://arxiv.org/format/2307.03222">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Cosmology and Nongalactic Astrophysics">astro-ph.CO</span> </div> </div> <p class="title is-5 mathjax"> Probing the two-body decaying dark matter scenario with weak lensing and the cosmic microwave background </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Bucko%2C+J">Jozef Bucko</a>, <a href="/search/?searchtype=author&query=Giri%2C+S+K">Sambit K. Giri</a>, <a href="/search/?searchtype=author&query=Peters%2C+F+H">Fabian Hervas Peters</a>, <a href="/search/?searchtype=author&query=Schneider%2C+A">Aurel Schneider</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="2307.03222v3-abstract-short" style="display: inline;"> Decaying dark matter (DDM) scenarios have recently regained attention due to their potential ability to resolve the well-known clustering (or $S_8$) tension between weak lensing (WL) and cosmic microwave background (CMB) measurements. In this paper, we investigate a well-established model where the original dark matter particle decays into a massless particle and a massive daughter particle. The l… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2307.03222v3-abstract-full').style.display = 'inline'; document.getElementById('2307.03222v3-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2307.03222v3-abstract-full" style="display: none;"> Decaying dark matter (DDM) scenarios have recently regained attention due to their potential ability to resolve the well-known clustering (or $S_8$) tension between weak lensing (WL) and cosmic microwave background (CMB) measurements. In this paper, we investigate a well-established model where the original dark matter particle decays into a massless particle and a massive daughter particle. The latter obtains a velocity kick during the decay process that results in the suppression of the matter power spectrum at scales that are observable with WL shear observations. We perform the first fully non-linear WL analysis of this two-body decaying dark matter ($螞$DDM) scenario, including intrinsic alignment and baryonic feedback processes. We used the cosmic shear band power spectra from \textit{KiDS-1000} data and combined it with temperature and polarisation data from \texttt{Planck} in order to constrain the $螞$DDM model. We report new limits on the decay rate and mass splitting parameters that are significantly stronger than previous results, especially in the case of low-mass splittings. Regarding the $S_8$ tension, we found a reduction from about 3 to 2 $蟽$, depending on which statistical measure is applied. We therefore conclude that the two-body $螞$DDM model is able to reduce the $S_8$ tension without convincingly solving it. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2307.03222v3-abstract-full').style.display = 'none'; document.getElementById('2307.03222v3-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 April, 2024; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 6 July, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> July 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">15 pages, 13 figures</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Report number:</span> NORDITA 2023-020 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2305.15466">arXiv:2305.15466</a> <span> [<a href="https://arxiv.org/pdf/2305.15466">pdf</a>, <a href="https://arxiv.org/format/2305.15466">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link 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="Astrophysics of Galaxies">astro-ph.GA</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/10.1093/mnras/stad2937">10.1093/mnras/stad2937 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> BEoRN: A fast and flexible framework to simulate the epoch of reionisation and cosmic dawn </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Schaeffer%2C+T">Timoth茅e Schaeffer</a>, <a href="/search/?searchtype=author&query=Giri%2C+S+K">Sambit K. Giri</a>, <a href="/search/?searchtype=author&query=Schneider%2C+A">Aurel Schneider</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="2305.15466v2-abstract-short" style="display: inline;"> In this study, we introduce BEoRN (Bubbles during the Epoch of Reionisation Numerical Simulator), a publicly available Python code that generates three-dimensional maps of the 21-cm signal from the cosmic dawn and the epoch of reionisation. Built upon N-body simulation outputs, BEoRN populates haloes with stars and galaxies based on a flexible source model. It then computes the evolution of Lyman-… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2305.15466v2-abstract-full').style.display = 'inline'; document.getElementById('2305.15466v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2305.15466v2-abstract-full" style="display: none;"> In this study, we introduce BEoRN (Bubbles during the Epoch of Reionisation Numerical Simulator), a publicly available Python code that generates three-dimensional maps of the 21-cm signal from the cosmic dawn and the epoch of reionisation. Built upon N-body simulation outputs, BEoRN populates haloes with stars and galaxies based on a flexible source model. It then computes the evolution of Lyman-$伪$ coupling, temperature, and ionisation profiles as a function of source properties, and paints these profiles around each source onto a three-dimensional grid. The code consistently deals with the overlap of ionised bubbles by redistributing photons around the bubble boundaries, thereby ensuring photon conservation. It accounts for the redshifting of photons and the source look-back effect for the temperature and Lyman-$伪$ coupling profiles which extend far into the intergalactic medium to scales of order 100 cMpc. We provide a detailed description of the code and compare it to results from the literature. After validation, we run three different benchmark models based on a cosmological N-body simulation. All three models agree with current observations from UV luminosity functions and estimates of the mean ionisation fraction. Due to different assumptions regarding the small-mass stellar-to-halo relation, the X-ray flux emission, and the ionising photon escape fraction, the models produce unique signatures ranging from a cold reionisation with deep absorption trough to an emission-dominated 21-cm signal, broadly encompassing the current uncertainties at cosmic dawn. The code BEoRN is publicly available at https://github.com/cosmic-reionization/BEoRN. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2305.15466v2-abstract-full').style.display = 'none'; document.getElementById('2305.15466v2-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 May, 2023; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 24 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">Report number:</span> NORDITA 2023-019 </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> MNRAS, Volume 526, Issue 2, December 2023, Pages 2942 2959 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2304.02661">arXiv:2304.02661</a> <span> [<a href="https://arxiv.org/pdf/2304.02661">pdf</a>, <a href="https://arxiv.org/format/2304.02661">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Instrumentation and Methods for Astrophysics">astro-ph.IM</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Cosmology and Nongalactic Astrophysics">astro-ph.CO</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/10.1093/mnras/stae257">10.1093/mnras/stae257 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Deep learning approach for identification of HII regions during reionization in 21-cm observations -- II. foreground contamination </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Bianco%2C+M">Michele Bianco</a>, <a href="/search/?searchtype=author&query=Giri%2C+S+K">Sambit. K. Giri</a>, <a href="/search/?searchtype=author&query=Prelogovi%C4%87%2C+D">David Prelogovi膰</a>, <a href="/search/?searchtype=author&query=Chen%2C+T">Tianyue Chen</a>, <a href="/search/?searchtype=author&query=Mertens%2C+F+G">Florent G. Mertens</a>, <a href="/search/?searchtype=author&query=Tolley%2C+E">Emma Tolley</a>, <a href="/search/?searchtype=author&query=Mesinger%2C+A">Andrei Mesinger</a>, <a href="/search/?searchtype=author&query=Kneib%2C+J">Jean-Paul Kneib</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="2304.02661v2-abstract-short" style="display: inline;"> The upcoming Square Kilometre Array Observatory (SKAO) will produce images of neutral hydrogen distribution during the epoch of reionization by observing the corresponding 21-cm signal. However, the 21-cm signal will be subject to instrumental limitations such as noise and galactic foreground contamination which pose a challenge for accurate detection. In this study, we present the SegU-Net v2 fra… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2304.02661v2-abstract-full').style.display = 'inline'; document.getElementById('2304.02661v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2304.02661v2-abstract-full" style="display: none;"> The upcoming Square Kilometre Array Observatory (SKAO) will produce images of neutral hydrogen distribution during the epoch of reionization by observing the corresponding 21-cm signal. However, the 21-cm signal will be subject to instrumental limitations such as noise and galactic foreground contamination which pose a challenge for accurate detection. In this study, we present the SegU-Net v2 framework, an enhanced version of our convolutional neural network, built to identify neutral and ionized regions in the 21-cm signal contaminated with foreground emission. We trained our neural network on 21-cm image data processed by a foreground removal method based on Principal Component Analysis achieving an average classification accuracy of 71 per cent between redshift $z=7$ to $11$. We tested SegU-Net v2 against various foreground removal methods, including Gaussian Process Regression, Polynomial Fitting, and Foreground-Wedge Removal. Results show comparable performance, highlighting SegU-Net v2's independence on these pre-processing methods. Statistical analysis shows that a perfect classification score with $AUC=95\%$ is possible for $8<z<10$. While the network prediction lacks the ability to correctly identify ionized regions at higher redshift and differentiate well the few remaining neutral regions at lower redshift due to low contrast between 21-cm signal, noise and foreground residual in images. Moreover, as the photon sources driving reionization are expected to be located inside ionised regions, we show that SegU-Net v2 can be used to correctly identify and measure the volume of isolated bubbles with $V_{\rm ion}>(10\, {\rm cMpc})^3$ at $z>9$, for follow-up studies with infrared/optical telescopes to detect these sources. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2304.02661v2-abstract-full').style.display = 'none'; document.getElementById('2304.02661v2-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, 2024; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 5 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">19 pages, 10 figures, 3 tables, 2 appendixes</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Report number:</span> NORDITA 2023-013 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2303.14239">arXiv:2303.14239</a> <span> [<a href="https://arxiv.org/pdf/2303.14239">pdf</a>, <a href="https://arxiv.org/format/2303.14239">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link 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="Astrophysics of Galaxies">astro-ph.GA</span> </div> </div> <p class="title is-5 mathjax"> Warm dark matter constraints from the JWST </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Dayal%2C+P">Pratika Dayal</a>, <a href="/search/?searchtype=author&query=Giri%2C+S+K">Sambit K. Giri</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="2303.14239v2-abstract-short" style="display: inline;"> Warm Dark Matter (WDM) particles with masses ($\sim$ kilo electronvolt) offer an attractive solution to the small-scale issues faced by the Cold Dark Matter (CDM) paradigm. The delay of structure formation in WDM models and the associated dearth of low-mass systems at high-redshifts makes this an ideal time to revisit WDM constraints in light of the unprecedented data-sets from the James Webb Spac… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2303.14239v2-abstract-full').style.display = 'inline'; document.getElementById('2303.14239v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2303.14239v2-abstract-full" style="display: none;"> Warm Dark Matter (WDM) particles with masses ($\sim$ kilo electronvolt) offer an attractive solution to the small-scale issues faced by the Cold Dark Matter (CDM) paradigm. The delay of structure formation in WDM models and the associated dearth of low-mass systems at high-redshifts makes this an ideal time to revisit WDM constraints in light of the unprecedented data-sets from the James Webb Space Telescope (JWST). Developing a phenomenological model based on the halo mass functions in CDM and WDM models, we calculate high-redshift ($z \gt 6$) the stellar mass functions (SMF) and the associated stellar mass density (SMD) and the maximum stellar mass allowed in a given volume. We find that: (i) WDM as light as 1.5 keV is already disfavoured by the low-mass end of the SMF (stellar mass $M_* \sim 10^7 \rm{M_\odot}$) although caution must be exerted given the impact of lensing uncertainties; (ii) 1.5 keV WDM models predict SMD values that show a steep decrease from $10^{8.8}$ to $10^{2} ~{\rm M_\odot ~cMpc^{-3}}$ from $z \sim 4$ to 17 for $M_* \gt 10^8 \rm{M_\odot}$; (iii) the 1.5 keV WDM model predicts a sharp and earlier cut-off in the maximum stellar masses for a given number density (or volume) as compared to CDM or heavier WDM models. For example, with a number density of $10^{-3} \rm {cMpc^{-3}}$, 1.5 (3) KeV WDM models do not predict bound objects at $z \gt 12$ (18). Forthcoming JWST observations of multiple blank fields can therefore be used as a strong probe of WDM at an epoch inaccessible by other means. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2303.14239v2-abstract-full').style.display = 'none'; document.getElementById('2303.14239v2-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> 9 January, 2024; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 24 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">Accepted to MNRAS</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Report number:</span> NORDITA-2023-009 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2303.08024">arXiv:2303.08024</a> <span> [<a href="https://arxiv.org/pdf/2303.08024">pdf</a>, <a href="https://arxiv.org/format/2303.08024">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link 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="Astrophysics of Galaxies">astro-ph.GA</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/10.1093/mnras/stad1852">10.1093/mnras/stad1852 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Starbursts in low-mass haloes at Cosmic Dawn. I. The critical halo mass for star formation </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Nebrin%2C+O">Olof Nebrin</a>, <a href="/search/?searchtype=author&query=Giri%2C+S+K">Sambit K. Giri</a>, <a href="/search/?searchtype=author&query=Mellema%2C+G">Garrelt Mellema</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="2303.08024v2-abstract-short" style="display: inline;"> The first stars, galaxies, star clusters, and direct-collapse black holes are expected to have formed in low-mass ($\sim$$10^{5}-10^{9} ~ M_{\odot}$) haloes at Cosmic Dawn ($z \sim 10 - 30$) under conditions of efficient gas cooling, leading to gas collapse towards the centre of the halo. The halo mass cooling threshold has been analyzed by several authors using both analytical models and numerica… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2303.08024v2-abstract-full').style.display = 'inline'; document.getElementById('2303.08024v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2303.08024v2-abstract-full" style="display: none;"> The first stars, galaxies, star clusters, and direct-collapse black holes are expected to have formed in low-mass ($\sim$$10^{5}-10^{9} ~ M_{\odot}$) haloes at Cosmic Dawn ($z \sim 10 - 30$) under conditions of efficient gas cooling, leading to gas collapse towards the centre of the halo. The halo mass cooling threshold has been analyzed by several authors using both analytical models and numerical simulations, with differing results. Since the halo number density is a sensitive function of the halo mass, an accurate model of the cooling threshold is needed for (semi-)analytical models of star formation at Cosmic Dawn. In this paper the cooling threshold mass is calculated (semi-)analytically, considering the effects of H$_2$-cooling and formation (in the gas phase and on dust grains), cooling by atomic metals, Lyman-$伪$ cooling, photodissociation of H$_2$ by Lyman-Werner photons (including self-shielding by H$_2$), photodetachment of H$^-$ by infrared photons, photoevaporation by ionization fronts, and the effect of baryon streaming velocities. We compare the calculations to several high-resolution cosmological simulations, showing excellent agreement. We find that in regions of typical baryon streaming velocities, star formation is possible in haloes of mass $\gtrsim 1-2 \times 10^6 ~ M_{\odot}$ for $z \gtrsim 20$. By $z \sim 8$, the expected Lyman-Werner background suppresses star formation in all minihaloes below the atomic-cooling threshold ($T_{\rm vir} = 10^4 ~ \textrm{K}$). The halo mass cooling threshold increases by another factor of $\sim$$4$ following reionization, although this effect is slightly delayed ($z \sim 4-5$) because of effective self-shielding. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2303.08024v2-abstract-full').style.display = 'none'; document.getElementById('2303.08024v2-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> 18 June, 2023; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 14 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">22 pages, 10 figures. Accepted for publication in MNRAS</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Report number:</span> NORDITA-2023-008 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2302.06626">arXiv:2302.06626</a> <span> [<a href="https://arxiv.org/pdf/2302.06626">pdf</a>, <a href="https://arxiv.org/format/2302.06626">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Cosmology and Nongalactic Astrophysics">astro-ph.CO</span> </div> </div> <p class="title is-5 mathjax"> Cosmological forecast of the 21-cm power spectrum using the halo model of reionization </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Schneider%2C+A">Aurel Schneider</a>, <a href="/search/?searchtype=author&query=Schaeffer%2C+T">Timoth茅e Schaeffer</a>, <a href="/search/?searchtype=author&query=Giri%2C+S+K">Sambit K. Giri</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="2302.06626v1-abstract-short" style="display: inline;"> The 21-cm power spectrum of reionization is a promising probe for cosmology and fundamental physics. Exploiting this new observable, however, requires fast predictors capable of efficiently scanning the very large parameter space of cosmological and astrophysical uncertainties. In this paper, we introduce the halo model of reionization (HMreio), a new analytical tool that combines the halo model o… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2302.06626v1-abstract-full').style.display = 'inline'; document.getElementById('2302.06626v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2302.06626v1-abstract-full" style="display: none;"> The 21-cm power spectrum of reionization is a promising probe for cosmology and fundamental physics. Exploiting this new observable, however, requires fast predictors capable of efficiently scanning the very large parameter space of cosmological and astrophysical uncertainties. In this paper, we introduce the halo model of reionization (HMreio), a new analytical tool that combines the halo model of the cosmic dawn with the excursion-set bubble model for reionization, assuming an empirical correction factor to deal with overlapping ionization bubbles. First, HMreio is validated against results from the well-known semi-numerical code 21cmFAST, showing a good overall agreement for wave-modes of $k\lesssim 1$ h/Mpc. Based on this result, we perform a Monte-Carlo Markov-Chain (MCMC) forecast analysis assuming mock data from 1000-hour observations with the low-frequency part of the Square Kilometre Array (SKA) observatory. We simultaneously vary the six standard cosmological parameters together with seven astrophysical nuisance parameters quantifying the abundance and spectral properties of sources. Depending on the assumed theory error, we find very competitive constraints on cosmological parameters. In particular, it will be possible to conclusively test current cosmological tensions related to the Hubble parameter ($H_0$-tension) and the matter clustering amplitude ($S_8$-tension). Furthermore, the sum of the neutrino masses can be strongly constrained, making it possible to determine the neutrino mass hierarchy at the $\sim 90$ percent confidence level. However, these goals can only be achieved if the current modelling uncertainties are substantially reduced to below $\sim 3$ percent. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2302.06626v1-abstract-full').style.display = 'none'; document.getElementById('2302.06626v1-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 February, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> February 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">18 pages, 8 figures, comments welcome</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Report number:</span> NORDITA 2023-006 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2301.00469">arXiv:2301.00469</a> <span> [<a href="https://arxiv.org/pdf/2301.00469">pdf</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Chemical Physics">physics.chem-ph</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Atomic and Molecular Clusters">physics.atm-clus</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/10.1021/acs.jpcc.3c00006">10.1021/acs.jpcc.3c00006 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Photodissociation of H$_2$ on Ag and Au Nanoparticles: Effect of Size, and Plasmon versus Inter-Band Transitions on Threshold Intensities for Dissociation </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Giri%2C+S+K">Sajal Kumar Giri</a>, <a href="/search/?searchtype=author&query=Schatz%2C+G+C">George C. Schatz</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="2301.00469v1-abstract-short" style="display: inline;"> This paper provides new insights concerning the simulation of plasmon driven chemical reactions using real-time TDDFT based on the tight-binding electronic structure code DFTB+, with applications to the dissociation of H$_2$ on octahedral silver and gold nanoparticles with 19-489 atoms. A new component of these calculations involves sampling a 300 K canonical ensemble to determine the distribution… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2301.00469v1-abstract-full').style.display = 'inline'; document.getElementById('2301.00469v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2301.00469v1-abstract-full" style="display: none;"> This paper provides new insights concerning the simulation of plasmon driven chemical reactions using real-time TDDFT based on the tight-binding electronic structure code DFTB+, with applications to the dissociation of H$_2$ on octahedral silver and gold nanoparticles with 19-489 atoms. A new component of these calculations involves sampling a 300 K canonical ensemble to determine the distribution of possible outcomes of the calculations, and with this approach we are able to determine the threshold for dissociation as a function of laser intensity, wavelength, and nanocluster size. We show that the threshold intensity varies as an inverse power of nanocluster size, which makes it possible to extrapolate the results to sizes that are more typical of experimental studies. The intensities obtained from this extrapolation are around a factor of 100 above powers used in the pulsed experiments. This is a closer comparison of theory and experiment than has been obtained in previous real-time simulations, and the remaining discrepancy can be understood in terms of electromagnetic hot spots that are associated with cluster formation. We also compare the influence of plasmon excitation versus inter-band excitation on reaction thresholds, revealing that for silver clusters plasmon excitation leads to lower thresholds, but for gold clusters, inter-band excitation is more effective. Our study also includes an analysis of charge transfer to and from the H$_2$ molecule, and a determination of orbital populations during and after the pulse, showing the correlation between metal excitations and the location of the antibonding level of H$_2$. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2301.00469v1-abstract-full').style.display = 'none'; document.getElementById('2301.00469v1-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, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> January 2023. </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2211.14334">arXiv:2211.14334</a> <span> [<a href="https://arxiv.org/pdf/2211.14334">pdf</a>, <a href="https://arxiv.org/format/2211.14334">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Cosmology and Nongalactic Astrophysics">astro-ph.CO</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/10.1051/0004-6361/202245562">10.1051/0004-6361/202245562 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Constraining dark matter decays with cosmic microwave background and weak lensing shear observations </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Bucko%2C+J">Jozef Bucko</a>, <a href="/search/?searchtype=author&query=Giri%2C+S+K">Sambit K. Giri</a>, <a href="/search/?searchtype=author&query=Schneider%2C+A">Aurel Schneider</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="2211.14334v2-abstract-short" style="display: inline;"> From observations at low and high redshifts, it is well known that the bulk of dark matter (DM) has to be stable or at least very long-lived. However, the possibility that a small fraction of DM is unstable or that all DM decays with a half-life time ($蟿$) significantly longer than the age of the Universe is not ruled out. One-body decaying dark matter (DDM) consists of a minimal extension to the… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2211.14334v2-abstract-full').style.display = 'inline'; document.getElementById('2211.14334v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2211.14334v2-abstract-full" style="display: none;"> From observations at low and high redshifts, it is well known that the bulk of dark matter (DM) has to be stable or at least very long-lived. However, the possibility that a small fraction of DM is unstable or that all DM decays with a half-life time ($蟿$) significantly longer than the age of the Universe is not ruled out. One-body decaying dark matter (DDM) consists of a minimal extension to the $螞$CDM model. It causes a modification of the cosmic growth history as well as a suppression of the small-scale clustering signal, providing interesting consequences regarding the $S_8$ tension, which is the observed difference in the clustering amplitude between weak-lensing (WL) and cosmic microwave background (CMB) observations. In this paper, we investigate models in which a fraction or all DM decays into radiation, focusing on the long-lived regime, that is, $蟿\gtrsim H_0^{-1}$ ( $H_0^{-1}$ being the Hubble time). We used WL data from the Kilo-Degree Survey (KiDS) and CMB data from Planck. First, we confirm that this DDM model cannot alleviate the $S_8$ difference. We then show that the most constraining power for DM decay does not come from the nonlinear WL data, but from CMB via the integrated Sachs-Wolfe effect. From the CMB data alone, we obtain constraints of $蟿\geq 288$~Gyr if all DM is assumed to be unstable, and we show that a maximum fraction of $f=0.07$ is allowed to decay assuming the half-life time to be comparable to (or shorter than) one Hubble time. The constraints from the KiDS-1000 WL data are significantly weaker, $蟿\geq 60$~Gyr and $f<0.34$. Combining the CMB and WL data does not yield tighter constraints than the CMB alone, except for short half-life times, for which the maximum allowed fraction becomes $f=0.03$. All limits are provided at the 95% confidence level. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2211.14334v2-abstract-full').style.display = 'none'; document.getElementById('2211.14334v2-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 March, 2023; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 25 November, 2022; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> November 2022. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> A&A 672, A157 (2023) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2209.07854">arXiv:2209.07854</a> <span> [<a href="https://arxiv.org/pdf/2209.07854">pdf</a>, <a href="https://arxiv.org/format/2209.07854">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link 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="Instrumentation and Methods for Astrophysics">astro-ph.IM</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/10.1051/0004-6361/202244316">10.1051/0004-6361/202244316 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Assessing the impact of two independent direction-dependent calibration algorithms on the LOFAR 21-cm signal power spectrum </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Gan%2C+H">H. Gan</a>, <a href="/search/?searchtype=author&query=Mertens%2C+F+G">F. G. Mertens</a>, <a href="/search/?searchtype=author&query=Koopmans%2C+L+V+E">L. V. E. Koopmans</a>, <a href="/search/?searchtype=author&query=Offringa%2C+A+R">A. R. Offringa</a>, <a href="/search/?searchtype=author&query=Mevius%2C+M">M. Mevius</a>, <a href="/search/?searchtype=author&query=Pandey%2C+V+N">V. N. Pandey</a>, <a href="/search/?searchtype=author&query=Brackenhoff%2C+S+A">S. A. Brackenhoff</a>, <a href="/search/?searchtype=author&query=Ceccotti%2C+E">E. Ceccotti</a>, <a href="/search/?searchtype=author&query=Ciardi%2C+B">B. Ciardi</a>, <a href="/search/?searchtype=author&query=Gehlot%2C+B+K">B. K. Gehlot</a>, <a href="/search/?searchtype=author&query=Ghara%2C+R">R. Ghara</a>, <a href="/search/?searchtype=author&query=Giri%2C+S+K">S. K. Giri</a>, <a href="/search/?searchtype=author&query=Iliev%2C+I+T">I. T. Iliev</a>, <a href="/search/?searchtype=author&query=Munshi%2C+S">S. Munshi</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="2209.07854v2-abstract-short" style="display: inline;"> Detecting the 21-cm signal from the Epoch of Reionisation (EoR) is challenging due to the strong astrophysical foregrounds, ionospheric effects, radio frequency interference and instrumental effects. Understanding and calibrating these effects are crucial for the detection. In this work, we introduce a newly developed direction-dependent (DD) calibration algorithm DDECAL and compare its performanc… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2209.07854v2-abstract-full').style.display = 'inline'; document.getElementById('2209.07854v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2209.07854v2-abstract-full" style="display: none;"> Detecting the 21-cm signal from the Epoch of Reionisation (EoR) is challenging due to the strong astrophysical foregrounds, ionospheric effects, radio frequency interference and instrumental effects. Understanding and calibrating these effects are crucial for the detection. In this work, we introduce a newly developed direction-dependent (DD) calibration algorithm DDECAL and compare its performance with an existing algorithm, SAGECAL, in the context of the LOFAR-EoR 21-cm power spectrum experiment. In our data set, the North Celestial Pole (NCP) and its flanking fields were observed simultaneously. We analyse the NCP and one of its flanking fields. The NCP field is calibrated by the standard pipeline, using SAGECAL with an extensive sky model and 122 directions, and the flanking field is calibrated by DDECAL and SAGECAL with a simpler sky model and 22 directions. Additionally, two strategies are used for subtracting Cassiopeia A and Cygnus A. The results show that DDECAL performs better at subtracting sources in the primary beam region due to the application of a beam model, while SAGECAL performs better at subtracting Cassiopeia A and Cygnus A. This indicates that including a beam model during DD calibration significantly improves the performance. The benefit is obvious in the primary beam region. We also compare the 21-cm power spectra on two different fields. The results show that the flanking field produces better upper limits compared to the NCP in this particular observation. Despite the minor differences between DDECAL and SAGECAL due to the beam application, we find that the two algorithms yield comparable 21-cm power spectra on the LOFAR-EoR data after foreground removal. Hence, the current LOFAR-EoR 21-cm power spectrum limits are not likely to depend on the DD calibration method. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2209.07854v2-abstract-full').style.display = 'none'; document.getElementById('2209.07854v2-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, 2024; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 16 September, 2022; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> September 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, 14 figures, accepted for publication in A&A; a few equations in section 3 were corrected in this version</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> A&A 669, A20 (2023) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2209.01225">arXiv:2209.01225</a> <span> [<a href="https://arxiv.org/pdf/2209.01225">pdf</a>, <a href="https://arxiv.org/format/2209.01225">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link 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="Astrophysics of Galaxies">astro-ph.GA</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/10.1051/0004-6361/202244986">10.1051/0004-6361/202244986 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Suppressing variance in 21-cm signal simulations during reionization </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Giri%2C+S+K">Sambit K. Giri</a>, <a href="/search/?searchtype=author&query=Schneider%2C+A">Aurel Schneider</a>, <a href="/search/?searchtype=author&query=Maion%2C+F">Francisco Maion</a>, <a href="/search/?searchtype=author&query=Angulo%2C+R+E">Raul E. Angulo</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="2209.01225v2-abstract-short" style="display: inline;"> Current best limits on the 21-cm signal during reionization are provided at large scales ($\gtrsim$100 Mpc). To model these scales, enormous simulation volumes are required which are computationally expensive. We find that the primary source of uncertainty at these large scales is sample variance, which decides the minimum size of simulations required to analyse current and upcoming observations.… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2209.01225v2-abstract-full').style.display = 'inline'; document.getElementById('2209.01225v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2209.01225v2-abstract-full" style="display: none;"> Current best limits on the 21-cm signal during reionization are provided at large scales ($\gtrsim$100 Mpc). To model these scales, enormous simulation volumes are required which are computationally expensive. We find that the primary source of uncertainty at these large scales is sample variance, which decides the minimum size of simulations required to analyse current and upcoming observations. In large-scale structure simulations, the method of `fixing' the initial conditions (ICs) to exactly follow the initial power spectrum and `pairing' two simulations with exactly out-of-phase ICs has been shown to significantly reduce sample variance. Here we apply this `fixing and pairing' (F\&P) approach to reionization simulations whose clustering signal originates from both density fluctuations and reionization bubbles. Using a semi-numerical code, we show that with the traditional method, simulation boxes of $L\simeq 500$ (300) Mpc are required to model the large-scale clustering signal at $k$=0.1 Mpc$^{-1}$ with a precision of 5 (10) per cent. Using F\&P, the simulation boxes can be reduced by a factor of 2 to obtain the same precision level. We conclude that the computing costs can be reduced by at least a factor of 4 when using the F\&P approach. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2209.01225v2-abstract-full').style.display = 'none'; document.getElementById('2209.01225v2-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 October, 2022; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 2 September, 2022; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> September 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">5 pages, 4 figures, accepted for publication in A&A</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> A&A 669, A6 (2023) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2203.15005">arXiv:2203.15005</a> <span> [<a href="https://arxiv.org/pdf/2203.15005">pdf</a>, <a href="https://arxiv.org/format/2203.15005">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Quantum Physics">quant-ph</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Mesoscale and Nanoscale Physics">cond-mat.mes-hall</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Applications">stat.AP</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/PhysRevE.106.024131">10.1103/PhysRevE.106.024131 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Controlling thermodynamics of a quantum heat engine with modulated amplitude drivings </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Giri%2C+S+K">Sajal Kumar Giri</a>, <a href="/search/?searchtype=author&query=Goswami%2C+H+P">Himangshu Prabal Goswami</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="2203.15005v1-abstract-short" style="display: inline;"> External driving of bath temperatures with a phase difference of a nonequilibrium quantum engine leads to the emergence of geometric effects on the thermodynamics. In this work, we modulate the amplitude of the external driving protocols by introducing envelope functions and study the role of geometric effects on the flux, noise and efficiency of a four-level driven quantum heat engine coupled wit… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2203.15005v1-abstract-full').style.display = 'inline'; document.getElementById('2203.15005v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2203.15005v1-abstract-full" style="display: none;"> External driving of bath temperatures with a phase difference of a nonequilibrium quantum engine leads to the emergence of geometric effects on the thermodynamics. In this work, we modulate the amplitude of the external driving protocols by introducing envelope functions and study the role of geometric effects on the flux, noise and efficiency of a four-level driven quantum heat engine coupled with two thermal baths and a unimodal cavity. We observe that having a finite width of the modulation envelope introduces an additional control knob for studying the thermodynamics in the adiabatic limit. The optimization of the flux as well as the noise with respect to thermally induced quantum coherences becomes possible in presence of geometric effects, which is hitherto not possible with sinusoidal driving without an envelope. We also report the deviation of the slope and generation of an intercept in the standard expression for efficiency at maximum power as a function of Carnot efficiency in presence of geometric effects under the amplitude modulation. Further, a recently developed universal bound on the efficiency obtained from thermodynamic uncertainty relation is shown not to hold when a small width of the modulation envelope along with a large value of cavity temperature is maintained. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2203.15005v1-abstract-full').style.display = 'none'; document.getElementById('2203.15005v1-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 March, 2022; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> March 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">8 pages, 6 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/2203.02345">arXiv:2203.02345</a> <span> [<a href="https://arxiv.org/pdf/2203.02345">pdf</a>, <a href="https://arxiv.org/format/2203.02345">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link 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="Instrumentation and Methods for Astrophysics">astro-ph.IM</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/10.1051/0004-6361/202142945">10.1051/0004-6361/202142945 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Statistical analysis of the causes of excess variance in the 21 cm signal power spectra obtained with the Low-Frequency Array </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Gan%2C+H">H. Gan</a>, <a href="/search/?searchtype=author&query=Koopmans%2C+L+V+E">L. V. E Koopmans</a>, <a href="/search/?searchtype=author&query=Mertens%2C+F+G">F. G. Mertens</a>, <a href="/search/?searchtype=author&query=Mevius%2C+M">M. Mevius</a>, <a href="/search/?searchtype=author&query=Offringa%2C+A+R">A. R. Offringa</a>, <a href="/search/?searchtype=author&query=Ciardi%2C+B">B. Ciardi</a>, <a href="/search/?searchtype=author&query=Gehlot%2C+B+K">B. K. Gehlot</a>, <a href="/search/?searchtype=author&query=Ghara%2C+R">R. Ghara</a>, <a href="/search/?searchtype=author&query=Ghosh%2C+A">A. Ghosh</a>, <a href="/search/?searchtype=author&query=Giri%2C+S+K">S. K. Giri</a>, <a href="/search/?searchtype=author&query=Iliev%2C+I+T">I. T. Iliev</a>, <a href="/search/?searchtype=author&query=Mellema%2C+G">G. Mellema</a>, <a href="/search/?searchtype=author&query=Pandey%2C+V+N">V. N. Pandey</a>, <a href="/search/?searchtype=author&query=Zaroubi%2C+S">S. Zaroubi</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="2203.02345v1-abstract-short" style="display: inline;"> The detection of the 21 cm signal of neutral hydrogen from the Epoch of Reionization (EoR) is challenging due to bright foreground sources, radio frequency interference (RFI), the ionosphere, and instrumental effects. Even after correcting for these effects in the calibration step and applying foreground removal techniques, the remaining residuals in the observed 21 cm power spectra are still abov… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2203.02345v1-abstract-full').style.display = 'inline'; document.getElementById('2203.02345v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2203.02345v1-abstract-full" style="display: none;"> The detection of the 21 cm signal of neutral hydrogen from the Epoch of Reionization (EoR) is challenging due to bright foreground sources, radio frequency interference (RFI), the ionosphere, and instrumental effects. Even after correcting for these effects in the calibration step and applying foreground removal techniques, the remaining residuals in the observed 21 cm power spectra are still above the thermal noise, which is referred to as the "excess variance." We study potential causes of this excess variance based on 13 nights of data obtained with the Low-Frequency Array (LOFAR). We focused on the impact of gain errors, the sky model, and ionospheric effects on the excess variance by correlating the relevant parameters such as the gain variance over time or frequency, local sidereal time (LST), diffractive scale, and phase structure-function slope with the level of excess variance. Our analysis shows that excess variance has an LST dependence, which is related to the power from the sky. And the simulated Stokes I power spectra from bright sources and the excess variance show a similar progression over LST with the minimum power appearing at LST bin 6h to 9h. This LST dependence is also present in sky images of the residual Stokes I of the observations. In very-wide sky images, we demonstrate that the extra power comes exactly from the direction of bright and distant sources Cassiopeia A and Cygnus A with the array beam patterns. These results suggest that the level of excess variance in the 21 cm signal power spectra is related to sky effects and, hence, it depends on LST. In particular, very bright and distant sources such as Cassiopeia A and Cygnus A can dominate the effect. This is in line with earlier studies and offers a path forward toward a solution since the correlation between the sky-related effects and the excess variance is non-negligible. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2203.02345v1-abstract-full').style.display = 'none'; document.getElementById('2203.02345v1-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> 4 March, 2022; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> March 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">29 pages, 14 figures, accepted for publication in A&A</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> A&A 663, A9 (2022) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2201.02210">arXiv:2201.02210</a> <span> [<a href="https://arxiv.org/pdf/2201.02210">pdf</a>, <a href="https://arxiv.org/format/2201.02210">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Cosmology and Nongalactic Astrophysics">astro-ph.CO</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.105.083011">10.1103/PhysRevD.105.083011 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Imprints of fermionic and bosonic mixed dark matter on the 21-cm signal at cosmic dawn </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Giri%2C+S+K">Sambit K. Giri</a>, <a href="/search/?searchtype=author&query=Schneider%2C+A">Aurel Schneider</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="2201.02210v2-abstract-short" style="display: inline;"> The 21-cm signal from the epoch of cosmic dawn prior to reionization consists of a promising observable to gain new insights into the dark matter (DM) sector. In this paper, we investigate its potential to constrain mixed (cold + non-cold) dark matter scenarios that are characterised by the non-cold DM fraction ($f_{\rm nCDM}$) and particle mass ($m_{\rm nCDM}$). As non-cold DM species, we investi… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2201.02210v2-abstract-full').style.display = 'inline'; document.getElementById('2201.02210v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2201.02210v2-abstract-full" style="display: none;"> The 21-cm signal from the epoch of cosmic dawn prior to reionization consists of a promising observable to gain new insights into the dark matter (DM) sector. In this paper, we investigate its potential to constrain mixed (cold + non-cold) dark matter scenarios that are characterised by the non-cold DM fraction ($f_{\rm nCDM}$) and particle mass ($m_{\rm nCDM}$). As non-cold DM species, we investigate both a fermionic (sterile neutrino) and a bosonic (ultra-light axion) particle. We show how these scenarios affect the global signal and the power spectrum using a halo-model implementation of the 21-cm signal at cosmic dawn. Next to this study, we perform an inference-based forecast study based on realistic mock power spectra from the Square Kilometre Array (SKA) telescope. Assuming inefficient, yet non-zero star-formation in minihaloes (i.e. haloes with mass below $10^8$ M$_{\odot}$), we obtain stringent constraints on both $m_{\rm nCDM}$ and $f_{\rm nCDM}$ that go well beyond current limits. Regarding the special case of $f_{\rm nCDM}\sim 1$, for example, we find a constraint of $m_{\rm nCDM}>15$ keV (thermal mass) for fermionic DM and $m_{\rm nCDM}>2\times10^{-20}$ eV for bosonic DM. For the opposite case of dominating cold DM, we find that at most one percent of the total DM abundance can be made of a hot fermionic or bosonic relic. All constraints are provided at the 95 percent confidence level. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2201.02210v2-abstract-full').style.display = 'none'; document.getElementById('2201.02210v2-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> 4 April, 2022; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 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">19 pages, 9 figures, similar to the version accepted for publication in PRD</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2112.00721">arXiv:2112.00721</a> <span> [<a href="https://arxiv.org/pdf/2112.00721">pdf</a>, <a href="https://arxiv.org/format/2112.00721">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Instrumentation and Methods for Astrophysics">astro-ph.IM</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Cosmology and Nongalactic Astrophysics">astro-ph.CO</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/10.1051/0004-6361/202142939">10.1051/0004-6361/202142939 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Degree-Scale Galactic Radio Emission at 122 MHz around the North Celestial Pole with LOFAR-AARTFAAC </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Gehlot%2C+B+K">B. K. Gehlot</a>, <a href="/search/?searchtype=author&query=Koopmans%2C+L+V+E">L. V. E. Koopmans</a>, <a href="/search/?searchtype=author&query=Offringa%2C+A+R">A. R. Offringa</a>, <a href="/search/?searchtype=author&query=Gan%2C+H">H. Gan</a>, <a href="/search/?searchtype=author&query=Ghara%2C+R">R. Ghara</a>, <a href="/search/?searchtype=author&query=Giri%2C+S+K">S. K. Giri</a>, <a href="/search/?searchtype=author&query=Kuiack%2C+M">M. Kuiack</a>, <a href="/search/?searchtype=author&query=Mertens%2C+F+G">F. G. Mertens</a>, <a href="/search/?searchtype=author&query=Mevius%2C+M">M. Mevius</a>, <a href="/search/?searchtype=author&query=Mondal%2C+R">R. Mondal</a>, <a href="/search/?searchtype=author&query=Pandey%2C+V+N">V. N. Pandey</a>, <a href="/search/?searchtype=author&query=Shulevski%2C+A">A. Shulevski</a>, <a href="/search/?searchtype=author&query=Wijers%2C+R+A+M+J">R. A. M. J. Wijers</a>, <a href="/search/?searchtype=author&query=Yatawatta%2C+S">S. Yatawatta</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="2112.00721v3-abstract-short" style="display: inline;"> Aims: Contamination from bright diffuse Galactic thermal and non-thermal radio emission poses crucial challenges in experiments aiming to measure the 21-cm signal of neutral hydrogen from the Cosmic Dawn and Epoch of Reionization. If not included in calibration, this diffuse emission can severely impact the analysis and signal extraction in 21-cm experiments. We examine large-scale diffuse Galacti… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2112.00721v3-abstract-full').style.display = 'inline'; document.getElementById('2112.00721v3-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2112.00721v3-abstract-full" style="display: none;"> Aims: Contamination from bright diffuse Galactic thermal and non-thermal radio emission poses crucial challenges in experiments aiming to measure the 21-cm signal of neutral hydrogen from the Cosmic Dawn and Epoch of Reionization. If not included in calibration, this diffuse emission can severely impact the analysis and signal extraction in 21-cm experiments. We examine large-scale diffuse Galactic emission at 122~MHz, around the North Celestial Pole, using the AARTFAAC-HBA system. Methods: In this pilot project, we present the first-ever wide-field image produced with a single sub-band of the data recorded with the AARTFAAC-HBA. We demonstrate two methods: multiscale CLEAN and shapelet decomposition, to model the diffuse emission revealed in the image. We use angular power spectrum metrics to quantify different components of the emission and compare the performance of the two diffuse structure modelling approaches. Results: We observe that the point sources dominate the angular power spectrum ($\ell(\ell+1)C_{\ell}/2蟺\equiv 螖^2(\ell)$) of the emission in the field on scales $\ell\gtrsim 60$ ($\lesssim 3$~degree). The angular power spectrum after subtraction of compact sources is flat within $20\lesssim \ell \lesssim200$ range, suggesting that the residual power is dominated by the diffuse emission on scales $\ell\lesssim200$. The residual diffuse emission has a brightness temperature variance of $螖^2_{\ell=180} = (145.64 \pm 13.61)~{\rm K}^2$ at 122~MHz on angular scales of 1~degree, and is consistent with a power-law following $C_{\ell}\propto \ell^{-2.0}$ in $20\lesssim \ell \lesssim200$ range. We also find that, in the current setup, the multiscale CLEAN is suitable to model the compact and diffuse structures on a wide range of angular scales, whereas the shapelet decomposition method better models the large scales, which are of the order of a few degrees and wider. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2112.00721v3-abstract-full').style.display = 'none'; document.getElementById('2112.00721v3-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 April, 2022; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 1 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">11 pages, 9 figures, accepted (A&A)</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> A&A 662, A97 (2022) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2111.02537">arXiv:2111.02537</a> <span> [<a href="https://arxiv.org/pdf/2111.02537">pdf</a>, <a href="https://arxiv.org/format/2111.02537">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link 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="Instrumentation and Methods for Astrophysics">astro-ph.IM</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/10.1093/mnras/stab3233">10.1093/mnras/stab3233 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> A numerical study of 21-cm signal suppression and noise increase in direction-dependent calibration of LOFAR data </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Mevius%2C+M">M. Mevius</a>, <a href="/search/?searchtype=author&query=Mertens%2C+F">F. Mertens</a>, <a href="/search/?searchtype=author&query=Koopmans%2C+L+V+E">L. V. E. Koopmans</a>, <a href="/search/?searchtype=author&query=Offringa%2C+A+R">A. R. Offringa</a>, <a href="/search/?searchtype=author&query=Yatawatta%2C+S">S. Yatawatta</a>, <a href="/search/?searchtype=author&query=Brentjens%2C+M+A">M. A. Brentjens</a>, <a href="/search/?searchtype=author&query=Chapman%2C+E">E. Chapman</a>, <a href="/search/?searchtype=author&query=Ciardi%2C+B">B. Ciardi</a>, <a href="/search/?searchtype=author&query=Gan%2C+H">H. Gan</a>, <a href="/search/?searchtype=author&query=Gehlot%2C+B+K">B. K. Gehlot</a>, <a href="/search/?searchtype=author&query=Ghara%2C+R">R. Ghara</a>, <a href="/search/?searchtype=author&query=Ghosh%2C+A">A. Ghosh</a>, <a href="/search/?searchtype=author&query=Giri%2C+S+K">S. K. Giri</a>, <a href="/search/?searchtype=author&query=Iliev%2C+I+T">I. T. Iliev</a>, <a href="/search/?searchtype=author&query=Mellema%2C+G">G. Mellema</a>, <a href="/search/?searchtype=author&query=Pandey%2C+V+N">V. N. Pandey</a>, <a href="/search/?searchtype=author&query=Zaroubi%2C+S">S. Zaroubi</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="2111.02537v1-abstract-short" style="display: inline;"> We investigate systematic effects in direction dependent gain calibration in the context of the Low-Frequency Array (LOFAR) 21-cm Epoch of Reionization (EoR) experiment. The LOFAR EoR Key Science Project aims to detect the 21-cm signal of neutral hydrogen on interferometric baselines of $50-250 位$. We show that suppression of faint signals can effectively be avoided by calibrating these short base… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2111.02537v1-abstract-full').style.display = 'inline'; document.getElementById('2111.02537v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2111.02537v1-abstract-full" style="display: none;"> We investigate systematic effects in direction dependent gain calibration in the context of the Low-Frequency Array (LOFAR) 21-cm Epoch of Reionization (EoR) experiment. The LOFAR EoR Key Science Project aims to detect the 21-cm signal of neutral hydrogen on interferometric baselines of $50-250 位$. We show that suppression of faint signals can effectively be avoided by calibrating these short baselines using only the longer baselines. However, this approach causes an excess variance on the short baselines due to small gain errors induced by overfitting during calibration. We apply a regularised expectation-maximisation algorithm with consensus optimisation (sagecal-co) to real data with simulated signals to show that overfitting can be largely mitigated by penalising spectrally non-smooth gain solutions during calibration. This reduces the excess power with about a factor 4 in the simulations. Our results agree with earlier theoretical analysis of this bias-variance trade off and support the gain-calibration approach to the LOFAR 21-cm signal data. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2111.02537v1-abstract-full').style.display = 'none'; document.getElementById('2111.02537v1-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> 3 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">This is a pre-copyedited, author-produced PDF of an article accepted for publication in MNRAS following peer review</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> MNRAS 2021 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2110.13190">arXiv:2110.13190</a> <span> [<a href="https://arxiv.org/pdf/2110.13190">pdf</a>, <a href="https://arxiv.org/format/2110.13190">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Cosmology and Nongalactic Astrophysics">astro-ph.CO</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/10.1093/mnras/stac1230">10.1093/mnras/stac1230 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> The large-scale 21-cm power spectrum from reionization </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Georgiev%2C+I">Ivelin Georgiev</a>, <a href="/search/?searchtype=author&query=Mellema%2C+G">Garrelt Mellema</a>, <a href="/search/?searchtype=author&query=Giri%2C+S+K">Sambit K. Giri</a>, <a href="/search/?searchtype=author&query=Mondal%2C+R">Rajesh Mondal</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="2110.13190v2-abstract-short" style="display: inline;"> Radio interferometers, such as the Low-Frequency Array and the future Square Kilometre Array, are attempting to measure the spherically averaged 21-cm power spectrum from the Epoch of Reionization. Understanding of the dominant physical processes which influence the power spectrum at each length-scale is therefore crucial for interpreting any future detection. We study a decomposition of the 21-cm… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2110.13190v2-abstract-full').style.display = 'inline'; document.getElementById('2110.13190v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2110.13190v2-abstract-full" style="display: none;"> Radio interferometers, such as the Low-Frequency Array and the future Square Kilometre Array, are attempting to measure the spherically averaged 21-cm power spectrum from the Epoch of Reionization. Understanding of the dominant physical processes which influence the power spectrum at each length-scale is therefore crucial for interpreting any future detection. We study a decomposition of the 21-cm power spectrum and quantify the evolution of its constituent terms for a set of numerical and semi-numerical simulations of a volume of $(714~\mathrm{Mpc})^3$, focusing on large scales with $k\lesssim 0.3$~Mpc$^{-1}$. We find that after $\sim 10$ per cent of the Universe has been ionized, the 21-cm power spectrum follows the power spectrum of neutral hydrogen fluctuations, which itself beyond a certain scale follows the matter power spectrum. Hence the signal has a two-regime form where the large-scale signal is a biased version of the cosmological density field, and the small-scale power spectrum is determined by the astrophysics of reionization. We construct a bias parameter to investigate the relation between the large-scale 21-cm signal and the cosmological density field. We find that the transition scale between the scale-independent and scale-dependent bias regimes is directly related to the value of the mean free path of ionizing photons ($位_{\mathrm{MFP}}$), and is characterised by the empirical formula $k_{\mathrm{trans}} \approx 2/位_{\mathrm{MFP}}$. Furthermore, we show that the numerical implementation of the mean free path effect has a significant impact on the shape of this transition. Most notably, the transition is more gradual if the mean free path effect is implemented as an absorption process rather than as a barrier. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2110.13190v2-abstract-full').style.display = 'none'; document.getElementById('2110.13190v2-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 May, 2022; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 25 October, 2021; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> October 2021. </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2110.02228">arXiv:2110.02228</a> <span> [<a href="https://arxiv.org/pdf/2110.02228">pdf</a>, <a href="https://arxiv.org/format/2110.02228">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Cosmology and Nongalactic Astrophysics">astro-ph.CO</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/10.1093/mnras/stac1493">10.1093/mnras/stac1493 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Constraining baryonic feedback and cosmology with weak-lensing, X-ray, and kinematic Sunyaev-Zeldovich observations </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Schneider%2C+A">Aurel Schneider</a>, <a href="/search/?searchtype=author&query=Giri%2C+S+K">Sambit K. Giri</a>, <a href="/search/?searchtype=author&query=Amodeo%2C+S">Stefania Amodeo</a>, <a href="/search/?searchtype=author&query=Refregier%2C+A">Alexandre Refregier</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="2110.02228v2-abstract-short" style="display: inline;"> Modern weak-lensing observations are becoming increasingly sensitive to baryonic feedback processes which are still poorly understood. So far, this challenge has been faced either by imposing scale-cuts in the data or by modelling baryonic effects with simple, one-parameter models. In this paper, we rely on a more general, seven-parameter prescription of baryonic feedback effects, which is primari… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2110.02228v2-abstract-full').style.display = 'inline'; document.getElementById('2110.02228v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2110.02228v2-abstract-full" style="display: none;"> Modern weak-lensing observations are becoming increasingly sensitive to baryonic feedback processes which are still poorly understood. So far, this challenge has been faced either by imposing scale-cuts in the data or by modelling baryonic effects with simple, one-parameter models. In this paper, we rely on a more general, seven-parameter prescription of baryonic feedback effects, which is primarily motivated by observations and has been shown to agree with a plethora of hydrodynamical simulations. By combining weak-lensing data from the Kilo-Degree Survey (KiDS-1000) with observations of gas around galaxy clusters, we are able to constrain baryonic parameters and learn more about feedback and cosmology. In particular, we use cluster gas fractions from X-ray data and gas profiles from kinematic Sunyaev-Zeldovich (kSZ) observations to provide evidence for baryonic feedback that is stronger than predicted by most hydrodynamical simulations. In terms of the matter power spectrum, we report a beyond-percent effect at wave-modes above $k\sim 0.1-0.45$ h/Mpc and a maximum suppression of $12-33$ percent at $k\sim7$ h/Mpc (68 percent confidence level). Regarding the combined parameter $危_8=蟽_8(惟_m/0.3)^{0.58}$, we find the known tension with the Planck satellite data to be reduced from 3.8 to 2.9 $蟽$ once baryonic effects are fully included in the analysis pipeline. The tension is further decreased to 2.6 $蟽$ when the weak-lensing data is combined with X-ray and kSZ observations. We conclude that, while baryonic feedback effects become more important in modern weak-lensing surveys, they are unlikely to act as the main culprit for the observed $危_8$-tension. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2110.02228v2-abstract-full').style.display = 'none'; document.getElementById('2110.02228v2-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, 2022; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 5 October, 2021; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> October 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">14 pages, 9 figures, published in MNRAS</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2108.12640">arXiv:2108.12640</a> <span> [<a href="https://arxiv.org/pdf/2108.12640">pdf</a>, <a href="https://arxiv.org/format/2108.12640">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Materials Science">cond-mat.mtrl-sci</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/PhysRevB.104.224432">10.1103/PhysRevB.104.224432 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Tuning magnetocaloric effect by optimizing thickness induced 3D strain state </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Giri%2C+S+K">Samir Kumar Giri</a>, <a href="/search/?searchtype=author&query=Akram%2C+W">Wasim Akram</a>, <a href="/search/?searchtype=author&query=Bansal%2C+M">Manisha Bansal</a>, <a href="/search/?searchtype=author&query=Maity%2C+T">Tuhin Maity</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="2108.12640v1-abstract-short" style="display: inline;"> The effect of 3-dimensional strain state on the magnetocaloric properties of epitaxial La0.8Ca0.2MnO3 (LCMO) thin films grown on two types of substrates, SrTiO3 (001) (STO) and LaAlO3 (001) (LAO) has been studied as a function of film thickness within the range of 25 to 300 nm. The STO substrate imposes an in-plane tensile biaxial strain while LAO substrate imposes an in-plane compressive biaxial… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2108.12640v1-abstract-full').style.display = 'inline'; document.getElementById('2108.12640v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2108.12640v1-abstract-full" style="display: none;"> The effect of 3-dimensional strain state on the magnetocaloric properties of epitaxial La0.8Ca0.2MnO3 (LCMO) thin films grown on two types of substrates, SrTiO3 (001) (STO) and LaAlO3 (001) (LAO) has been studied as a function of film thickness within the range of 25 to 300 nm. The STO substrate imposes an in-plane tensile biaxial strain while LAO substrate imposes an in-plane compressive biaxial strain. The in-plane biaxial strain on LCMO by STO substrate gets relaxed more rapidly than that by LAO substrate but both LCMO/STO and LCMO/LAO show a maximum entropy change of 12.1 J/Kg-K and 3.2 J/Kg-K, respectively at a critical thickness of 75 nm (at 6 T applied magnetic field). LCMO/LAO is found to exhibit a wider transition temperature region with full width at half maxima (FWHM) 40 K of the dM/dT vs T curve compared to LCMO/STO with FWHM 33 K of that curve. This broadening of the transition region indicates that the Table like magnetocaloric effect (MCE) is attainable by changing the strain type. The maximum Relative Cooling Power, 361 J/Kg of LCMO/STO and 339 J/Kg of LCMO/LAO is also observed at the thickness 75 nm. The Curie temperature varies with the thickness exploring the variation of ferromagnetic interaction strength due to strain relaxation. The film thickness and substrate induced lattice strain are proved to be the significant parameters for controlling MCE. The highest MCE response at a particular thickness shows the possibility of tuning MCE in other devices by optimizing thickness. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2108.12640v1-abstract-full').style.display = 'none'; document.getElementById('2108.12640v1-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 August, 2021; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> August 2021. </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2108.12634">arXiv:2108.12634</a> <span> [<a href="https://arxiv.org/pdf/2108.12634">pdf</a>, <a href="https://arxiv.org/format/2108.12634">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Materials Science">cond-mat.mtrl-sci</span> </div> </div> <p class="title is-5 mathjax"> Tuneable vertical hysteresis loop shift in Ni80Fe20/SrRuO3 heterostructures </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Bansal%2C+M">Manisha Bansal</a>, <a href="/search/?searchtype=author&query=Giri%2C+S+K">Samir Kumar Giri</a>, <a href="/search/?searchtype=author&query=Li%2C+W">Weiwei Li</a>, <a href="/search/?searchtype=author&query=MacManus-Driscoll%2C+J+L">Judith L. MacManus-Driscoll</a>, <a href="/search/?searchtype=author&query=Maity%2C+T">Tuhin Maity</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="2108.12634v1-abstract-short" style="display: inline;"> A novel vertical hysteresis loop shift is observed for a bilayer thin film of Ni80Fe20/SrRuO3 (1:2 thickness ratio) on SrTiO3 substrate, after field cooled through the Curie temperature ~125 K of SrRuO3, whereas no shift is found for zero field cooled measurement. The vertical shift is noticed below ~125 K which increases with decreasing temperature and reaches a maximum of 33% at 2 K. The vertica… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2108.12634v1-abstract-full').style.display = 'inline'; document.getElementById('2108.12634v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2108.12634v1-abstract-full" style="display: none;"> A novel vertical hysteresis loop shift is observed for a bilayer thin film of Ni80Fe20/SrRuO3 (1:2 thickness ratio) on SrTiO3 substrate, after field cooled through the Curie temperature ~125 K of SrRuO3, whereas no shift is found for zero field cooled measurement. The vertical shift is noticed below ~125 K which increases with decreasing temperature and reaches a maximum of 33% at 2 K. The vertical shift is modelled closely using micromagnetic simulations. It is shown that the amount of vertical shift depends on the competition between the relative thicknesses and the anisotropies of the two films governed by Spring Thickness law and Imperial Law, respectively. We propose a generalized model of vertical shift which is applicable for other material systems, and hence could be informative for use of vertical shift in future spintronic devices. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2108.12634v1-abstract-full').style.display = 'none'; document.getElementById('2108.12634v1-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 August, 2021; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> August 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">9 pages, 13 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/2108.08863">arXiv:2108.08863</a> <span> [<a href="https://arxiv.org/pdf/2108.08863">pdf</a>, <a href="https://arxiv.org/format/2108.08863">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Cosmology and Nongalactic Astrophysics">astro-ph.CO</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/10.1088/1475-7516/2021/12/046">10.1088/1475-7516/2021/12/046 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Emulation of baryonic effects on the matter power spectrum and constraints from galaxy cluster data </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Giri%2C+S+K">Sambit K. Giri</a>, <a href="/search/?searchtype=author&query=Schneider%2C+A">Aurel Schneider</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="2108.08863v2-abstract-short" style="display: inline;"> Baryonic feedback effects consist of a major systematic for upcoming weak-lensing and galaxy-clustering surveys. In this paper, we present an emulator for the baryonic suppression of the matter power spectrum. The emulator is based on the baryonification model, containing seven free parameters that are connected to the gas profiles and stellar abundances in haloes. We show that with the baryonic e… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2108.08863v2-abstract-full').style.display = 'inline'; document.getElementById('2108.08863v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2108.08863v2-abstract-full" style="display: none;"> Baryonic feedback effects consist of a major systematic for upcoming weak-lensing and galaxy-clustering surveys. In this paper, we present an emulator for the baryonic suppression of the matter power spectrum. The emulator is based on the baryonification model, containing seven free parameters that are connected to the gas profiles and stellar abundances in haloes. We show that with the baryonic emulator, we can not only recover the power spectra of hydro-dynamical simulations at sub-percent precision but also establish a connection between the baryonic suppression of the power spectrum and the gas and stellar fractions in haloes. This connection allows us to predict the expected deviation from a dark-matter-only power spectrum using measured X-ray gas fractions of galaxy groups and clusters. With these measurements, we constrain the suppression to exceed the percent-level at k = 0.1-0.4 h/Mpc and to reach a maximum of 20-28 percent at around k = 7 h/Mpc (68 percent confidence level). As a further step, we also perform a detailed parameter study and we present a minimum set of four baryonic parameters that are required to recover the scale and redshift dependence observed in hydro-dynamical simulations. The baryonic emulator can be found at https://github.com/sambit-giri/BCemu. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2108.08863v2-abstract-full').style.display = 'none'; document.getElementById('2108.08863v2-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 December, 2021; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 19 August, 2021; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> August 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">33 pages, 16 figures, Accepted for publication in JCAP</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2106.04588">arXiv:2106.04588</a> <span> [<a href="https://arxiv.org/pdf/2106.04588">pdf</a>, <a href="https://arxiv.org/format/2106.04588">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Cosmology and Nongalactic Astrophysics">astro-ph.CO</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/10.1088/1475-7516/2021/12/044">10.1088/1475-7516/2021/12/044 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Mixed dark matter: matter power spectrum and halo mass function </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Parimbelli%2C+G">G. Parimbelli</a>, <a href="/search/?searchtype=author&query=Scelfo%2C+G">G. Scelfo</a>, <a href="/search/?searchtype=author&query=Giri%2C+S+K">S. K. Giri</a>, <a href="/search/?searchtype=author&query=Schneider%2C+A">A. Schneider</a>, <a href="/search/?searchtype=author&query=Archidiacono%2C+M">M. Archidiacono</a>, <a href="/search/?searchtype=author&query=Camera%2C+S">S. Camera</a>, <a href="/search/?searchtype=author&query=Viel%2C+M">M. Viel</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="2106.04588v2-abstract-short" style="display: inline;"> We investigate and quantify the impact of mixed (cold and warm) dark matter models on large-scale structure observables. In this scenario, dark matter comes in two phases, a cold one (CDM) and a warm one (WDM): the presence of the latter causes a suppression in the matter power spectrum which is allowed by current constraints and may be detected in present-day and upcoming surveys. We run a large… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2106.04588v2-abstract-full').style.display = 'inline'; document.getElementById('2106.04588v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2106.04588v2-abstract-full" style="display: none;"> We investigate and quantify the impact of mixed (cold and warm) dark matter models on large-scale structure observables. In this scenario, dark matter comes in two phases, a cold one (CDM) and a warm one (WDM): the presence of the latter causes a suppression in the matter power spectrum which is allowed by current constraints and may be detected in present-day and upcoming surveys. We run a large set of $N$-body simulations in order to build an efficient and accurate emulator to predict the aforementioned suppression with percent precision over a wide range of values for the WDM mass, $M_\mathrm{wdm}$, and its fraction with respect to the totality of dark matter, $f_\mathrm{wdm}$. The suppression in the matter power spectrum is found to be independent of changes in the cosmological parameters at the 2% level for $k\lesssim 10 \ h/$Mpc and $z\leq 3.5$. In the same ranges, by applying a baryonification procedure on both $螞$CDM and CWDM simulations to account for the effect of feedback, we find a similar level of agreement between the two scenarios. We examine the impact that such suppression has on weak lensing and angular galaxy clustering power spectra. Finally, we discuss the impact of mixed dark matter on the shape of the halo mass function and which analytical prescription yields the best agreement with simulations. We provide the reader with an application to galaxy cluster number counts. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2106.04588v2-abstract-full').style.display = 'none'; document.getElementById('2106.04588v2-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> 3 January, 2022; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 8 June, 2021; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> June 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">27 pages, 10 figures, minor changes after peer review</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> JCAP12(2021)044 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2104.07675">arXiv:2104.07675</a> <span> [<a href="https://arxiv.org/pdf/2104.07675">pdf</a>, <a href="https://arxiv.org/format/2104.07675">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Cosmology and Nongalactic Astrophysics">astro-ph.CO</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/10.1088/1475-7516/2021/10/040">10.1088/1475-7516/2021/10/040 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Decaying Dark Matter: Simulations and Weak-Lensing Forecast </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Hubert%2C+J">Jonathan Hubert</a>, <a href="/search/?searchtype=author&query=Schneider%2C+A">Aurel Schneider</a>, <a href="/search/?searchtype=author&query=Potter%2C+D">Doug Potter</a>, <a href="/search/?searchtype=author&query=Stadel%2C+J">Joachim Stadel</a>, <a href="/search/?searchtype=author&query=Giri%2C+S+K">Sambit K. Giri</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="2104.07675v2-abstract-short" style="display: inline;"> Despite evidence for the existence of dark matter (DM) from very high and low redshifts, a moderate amount of DM particle decay remains a valid possibility. This includes both models with very long-lived yet unstable particles or mixed scenarios where only a small fraction of dark matter is allowed to decay. In this paper, we investigate how DM particles decaying into radiation affect non-linear s… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2104.07675v2-abstract-full').style.display = 'inline'; document.getElementById('2104.07675v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2104.07675v2-abstract-full" style="display: none;"> Despite evidence for the existence of dark matter (DM) from very high and low redshifts, a moderate amount of DM particle decay remains a valid possibility. This includes both models with very long-lived yet unstable particles or mixed scenarios where only a small fraction of dark matter is allowed to decay. In this paper, we investigate how DM particles decaying into radiation affect non-linear structure formation. We look at the power spectrum and its redshift evolution, varying both the decay lifetime ($蟿$) and the fraction of decaying-to-total dark matter ($f$), and we propose a fitting function that reaches sub-percent precision below $k\sim10$ h/Mpc. Based on this fit, we perform a forecast analysis for a Euclid-like weak lensing (WL) survey, including both massive neutrino and baryonic feedback parameters. We find that with WL observations alone, it is possible to rule out decay lifetimes smaller than $蟿=75$ Gyr (at 95 percent CL) for the case that all DM is unstable. This constraint improves to $蟿=182$ Gyr if the WL data is combined with CMB priors from the Planck satellite and to $蟿=275$ Gyr if we further assume baryonic feedback to be fully constrained by upcoming Sunyaev-Zeldovich or X-ray data. The latter shows a factor of 3.2 improvement compared to constraints from CMB data alone. Regarding the scenario of a strongly decaying sub-component of dark matter with $蟿\sim 30$ Gyr or lower, it will be possible to rule out a decaying-to-total fraction of $f>0.49$, $f>0.21$, and $f>0.13$ (at the 95 percent CL) for the same three scenarios. We conclude that the upcoming stage-IV WL surveys will allow us to significantly improve current constraints on the stability of the dark matter sector. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2104.07675v2-abstract-full').style.display = 'none'; document.getElementById('2104.07675v2-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> 8 September, 2021; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 15 April, 2021; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> April 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">matching accepted version</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2103.07483">arXiv:2103.07483</a> <span> [<a href="https://arxiv.org/pdf/2103.07483">pdf</a>, <a href="https://arxiv.org/format/2103.07483">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Cosmology and Nongalactic Astrophysics">astro-ph.CO</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/10.1093/mnras/stab776">10.1093/mnras/stab776 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Constraining the state of the intergalactic medium during the Epoch of Reionization using MWA 21-cm signal observations </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Ghara%2C+R">Raghunath Ghara</a>, <a href="/search/?searchtype=author&query=Giri%2C+S+K">Sambit K. Giri</a>, <a href="/search/?searchtype=author&query=Ciardi%2C+B">Benedetta Ciardi</a>, <a href="/search/?searchtype=author&query=Mellema%2C+G">Garrelt Mellema</a>, <a href="/search/?searchtype=author&query=Zaroubi%2C+S">Saleem Zaroubi</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="2103.07483v1-abstract-short" style="display: inline;"> The Murchison Widefield Array (MWA) team has derived new upper limits on the spherically averaged power spectrum of the 21-cm signal at six redshifts in the range $z \approx 6.5-8.7$. We use these upper limits and a Bayesian inference framework to derive constraints on the ionization and thermal state of the intergalactic medium (IGM) as well as on the strength of a possible additional radio backg… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2103.07483v1-abstract-full').style.display = 'inline'; document.getElementById('2103.07483v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2103.07483v1-abstract-full" style="display: none;"> The Murchison Widefield Array (MWA) team has derived new upper limits on the spherically averaged power spectrum of the 21-cm signal at six redshifts in the range $z \approx 6.5-8.7$. We use these upper limits and a Bayesian inference framework to derive constraints on the ionization and thermal state of the intergalactic medium (IGM) as well as on the strength of a possible additional radio background. We do not find any constraints on the state of the IGM for $z\gtrsim 7.8$ if no additional radio background is present. In the presence of such a radio background, the 95 per cent credible intervals of the disfavoured models at redshift $\gtrsim 6.5 $ correspond to an IGM with a volume averaged fraction of ionized regions below 0.6 and an average gas temperature $\lesssim 10^3$ K. In these models, the heated regions are characterised by a temperature larger than that of the radio background, and by a distribution with characteristic size $\lesssim 10$ $h^{-1}$ Mpc and a full width at half maximum (FWHM) of $\lesssim 30$ $h^{-1}$ Mpc. Within the same credible interval limits, we exclude an additional radio background of at least $0.008\%$ of the CMB at 1.42 GHz. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2103.07483v1-abstract-full').style.display = 'none'; document.getElementById('2103.07483v1-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 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">13 Pages, 6 Figures, 5 Tables, Accepted for publication in MNRAS</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2102.06713">arXiv:2102.06713</a> <span> [<a href="https://arxiv.org/pdf/2102.06713">pdf</a>, <a href="https://arxiv.org/format/2102.06713">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Instrumentation and Methods for Astrophysics">astro-ph.IM</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Cosmology and Nongalactic Astrophysics">astro-ph.CO</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/10.1093/mnras/stab1518">10.1093/mnras/stab1518 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Deep learning approach for identification of HII regions during reionization in 21-cm observations </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Bianco%2C+M">Michele Bianco</a>, <a href="/search/?searchtype=author&query=Giri%2C+S+K">Sambit. K. Giri</a>, <a href="/search/?searchtype=author&query=Iliev%2C+I+T">Ilian T. Iliev</a>, <a href="/search/?searchtype=author&query=Mellema%2C+G">Garrelt Mellema</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="2102.06713v2-abstract-short" style="display: inline;"> The upcoming Square Kilometre Array (SKA-Low) will map the distribution of neutral hydrogen during reionization, and produce a tremendous amount of 3D tomographic data. These images cubes will be subject to instrumental limitations, such as noise and limited resolution. Here we present SegU-Net, a stable and reliable method for identification of neutral and ionized regions in these images. SegU-Ne… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2102.06713v2-abstract-full').style.display = 'inline'; document.getElementById('2102.06713v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2102.06713v2-abstract-full" style="display: none;"> The upcoming Square Kilometre Array (SKA-Low) will map the distribution of neutral hydrogen during reionization, and produce a tremendous amount of 3D tomographic data. These images cubes will be subject to instrumental limitations, such as noise and limited resolution. Here we present SegU-Net, a stable and reliable method for identification of neutral and ionized regions in these images. SegU-Net is a U-Net architecture based convolutional neural network (CNN) for image segmentation. It is capable of segmenting our image data into meaningful features (ionized and neutral regions) with greater accuracy compared to previous methods. We can estimate the true ionization history from our mock observation of SKA with an observation time of 1000 h with more than 87 per cent accuracy. We also show that SegU-Net can be used to recover various topological summary statistics, such as size distributions and Betti numbers, with a relative difference of only a few per cent. These summary statistics characterise the non-Gaussian nature of the reionization process. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2102.06713v2-abstract-full').style.display = 'none'; document.getElementById('2102.06713v2-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 June, 2021; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 12 February, 2021; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> February 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, 13 figures, 3 tables. Moderate and minor revision, consisting of rearranging sections and extend the discussion of the network uncertainty outputs</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2101.01712">arXiv:2101.01712</a> <span> [<a href="https://arxiv.org/pdf/2101.01712">pdf</a>, <a href="https://arxiv.org/format/2101.01712">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Cosmology and Nongalactic Astrophysics">astro-ph.CO</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/10.1093/mnras/stab787">10.1093/mnras/stab787 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> The impact of inhomogeneous subgrid clumping on cosmic reionization II: modelling stochasticity </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Bianco%2C+M">Michele Bianco</a>, <a href="/search/?searchtype=author&query=Iliev%2C+I+T">Ilian T. Iliev</a>, <a href="/search/?searchtype=author&query=Ahn%2C+K">Kyungjin Ahn</a>, <a href="/search/?searchtype=author&query=Giri%2C+S+K">Sambit K. Giri</a>, <a href="/search/?searchtype=author&query=Mao%2C+Y">Yi Mao</a>, <a href="/search/?searchtype=author&query=Park%2C+H">Hyunbae Park</a>, <a href="/search/?searchtype=author&query=Shapiro%2C+P+R">Paul R. Shapiro</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="2101.01712v2-abstract-short" style="display: inline;"> Small-scale density fluctuations can significantly affect reionization but are typically modelled quite crudely. Unresolved fluctuations in numerical simulations and analytical calculations are included using a gas clumping factor, typically assumed to be independent of the local environment. In Paper I, we presented an improved, local density-dependent model for the sub-grid gas clumping. Here we… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2101.01712v2-abstract-full').style.display = 'inline'; document.getElementById('2101.01712v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2101.01712v2-abstract-full" style="display: none;"> Small-scale density fluctuations can significantly affect reionization but are typically modelled quite crudely. Unresolved fluctuations in numerical simulations and analytical calculations are included using a gas clumping factor, typically assumed to be independent of the local environment. In Paper I, we presented an improved, local density-dependent model for the sub-grid gas clumping. Here we extend this using an empirical stochastic model based on the results from high-resolution numerical simulations which fully resolve all relevant fluctuations. Our model reproduces well both the mean density-clumping relation and its scatter. We applied our stochastic model, along with the mean clumping one and the Paper I deterministic model, to create a large-volume realisation of the clumping field, and used these in radiative transfer simulations of cosmic reionization. Our results show that the simplistic mean clumping model delays reionization compared to local density-dependent models, despite producing fewer recombinations overall. This is due to the very different spatial distribution of clumping, resulting in much higher photoionization rates in the latter cases. The mean clumping model produces smaller HII regions throughout most of the reionization, but those percolate faster at late times. It also causes a significant delay in the 21-cm fluctuations peak and yields lower non-Gaussianity and many fewer bright pixels in the PDF distribution. The stochastic density-dependent model shows relatively minor differences from the deterministic one, mostly concentrated around overlap, where it significantly suppresses the 21-cm fluctuations, and at the bright tail of the 21-cm PDFs, where it produces noticeably more bright pixels. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2101.01712v2-abstract-full').style.display = 'none'; document.getElementById('2101.01712v2-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 May, 2021; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 5 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">18 pages, 17 figures Minor change: enlarged the inset table in Fig. 1</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Monthly Notices of the Royal Astronomical Society: 24 March 2021 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2012.12908">arXiv:2012.12908</a> <span> [<a href="https://arxiv.org/pdf/2012.12908">pdf</a>, <a href="https://arxiv.org/format/2012.12908">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link 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="Astrophysics of Galaxies">astro-ph.GA</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/10.1093/mnras/stab1320">10.1093/mnras/stab1320 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Measuring the topology of reionization with Betti numbers </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Giri%2C+S+K">Sambit K. Giri</a>, <a href="/search/?searchtype=author&query=Mellema%2C+G">Garrelt Mellema</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="2012.12908v2-abstract-short" style="display: inline;"> The distribution of ionised hydrogen during the epoch of reionization (EoR) has a complex morphology. We propose to measure the three-dimensional topology of ionised regions using the Betti numbers. These quantify the topology using the number of components, tunnels and cavities in any given field. Based on the results for a set of reionization simulations we find that the Betti numbers of the ion… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2012.12908v2-abstract-full').style.display = 'inline'; document.getElementById('2012.12908v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2012.12908v2-abstract-full" style="display: none;"> The distribution of ionised hydrogen during the epoch of reionization (EoR) has a complex morphology. We propose to measure the three-dimensional topology of ionised regions using the Betti numbers. These quantify the topology using the number of components, tunnels and cavities in any given field. Based on the results for a set of reionization simulations we find that the Betti numbers of the ionisation field show a characteristic evolution during reionization, with peaks in the different Betti numbers characterising different stages of the process. The shapes of their evolutionary curves can be fitted with simple analytical functions. We also observe that the evolution of the Betti numbers shows a clear connection with the percolation of the ionized and neutral regions and differs between different reionization scenarios. Through these properties, the Betti numbers provide a more useful description of the topology than the widely studied Euler characteristic or genus. The morphology of the ionisation field will be imprinted on the redshifted 21-cm signal from the EoR. We construct mock image cubes using the properties of the low-frequency element of the future Square Kilometre Array and show that we can extract the Betti numbers from such datasets if an observation time of 1000 h is used. Even for a much shorter observation time of 100 h, some topological information can be extracted for the middle and later stages of reionization. We also find that the topological information extracted from the mock 21-cm observations can put constraints on reionization models. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2012.12908v2-abstract-full').style.display = 'none'; document.getElementById('2012.12908v2-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 May, 2021; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 23 December, 2020; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> December 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">15 pages, 11 figures, 3 tables. Accepted to MNRAS</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2011.12308">arXiv:2011.12308</a> <span> [<a href="https://arxiv.org/pdf/2011.12308">pdf</a>, <a href="https://arxiv.org/format/2011.12308">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link 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="Astrophysics of Galaxies">astro-ph.GA</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.103.083025">10.1103/PhysRevD.103.083025 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> A halo model approach for the 21-cm power spectrum at cosmic dawn </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Schneider%2C+A">Aurel Schneider</a>, <a href="/search/?searchtype=author&query=Giri%2C+S+K">Sambit K. Giri</a>, <a href="/search/?searchtype=author&query=Mirocha%2C+J">Jordan Mirocha</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="2011.12308v2-abstract-short" style="display: inline;"> Prior to the epoch of reionisation, the 21-cm signal of the cosmic dawn is dominated by the Lyman-$伪$ coupling and gas temperature fluctuations caused by the first sources of radiation. While early efforts to model this epoch relied on analytical techniques, the community quickly transitioned to more expensive semi-numerical models. Here, we re-assess the viability of simpler approaches that allow… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2011.12308v2-abstract-full').style.display = 'inline'; document.getElementById('2011.12308v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2011.12308v2-abstract-full" style="display: none;"> Prior to the epoch of reionisation, the 21-cm signal of the cosmic dawn is dominated by the Lyman-$伪$ coupling and gas temperature fluctuations caused by the first sources of radiation. While early efforts to model this epoch relied on analytical techniques, the community quickly transitioned to more expensive semi-numerical models. Here, we re-assess the viability of simpler approaches that allow for rapid explorations of the vast astrophysical parameter space. We propose a new analytical method to calculate the 21-cm power spectrum based on the framework of the halo model. Both the Lyman-$伪$ coupling and temperature fluctuations are described by overlapping radiation flux profiles that include spectral red-shifting and source attenuation due to look-back (light-cone) effects. The 21-cm halo model is compared to the semi-numerical code 21cmFAST exhibiting generally good agreement, i.e., the power spectra differ by less than a factor of three over a large range of $k$-modes and redshifts. We show that the remaining differences between the two methods are comparable to the expected variations from modelling uncertainties associated with the abundance, bias, and accretion rates of haloes. While these current uncertainties must be reduced in the future, our work suggests that inference at acceptable accuracy will become feasible with very efficient halo models of the cosmic dawn. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2011.12308v2-abstract-full').style.display = 'none'; document.getElementById('2011.12308v2-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 March, 2021; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 24 November, 2020; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> November 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">Accepted version (Phys.Rev.D)</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, 083025 (2021) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2011.03558">arXiv:2011.03558</a> <span> [<a href="https://arxiv.org/pdf/2011.03558">pdf</a>, <a href="https://arxiv.org/format/2011.03558">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link 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="Astrophysics of Galaxies">astro-ph.GA</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/10.1093/mnras/stab1822">10.1093/mnras/stab1822 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Redshift-space distortions in simulations of the 21-cm signal from the cosmic dawn </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Ross%2C+H+E">Hannah E. Ross</a>, <a href="/search/?searchtype=author&query=Giri%2C+S+K">Sambit K. Giri</a>, <a href="/search/?searchtype=author&query=Dixon%2C+K+L">Keri L. Dixon</a>, <a href="/search/?searchtype=author&query=Ghara%2C+R">Raghunath Ghara</a>, <a href="/search/?searchtype=author&query=Iliev%2C+I+T">Ilian T. Iliev</a>, <a href="/search/?searchtype=author&query=Mellema%2C+G">Garrelt Mellema</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="2011.03558v1-abstract-short" style="display: inline;"> The 21-cm signal from the Cosmic Dawn (CD) is likely to contain large fluctuations, with the most extreme astrophysical models on the verge of being ruled out by observations from radio interferometers. It is therefore vital that we understand not only the astrophysical processes governing this signal, but also other inherent processes impacting the signal itself, and in particular line-of-sight e… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2011.03558v1-abstract-full').style.display = 'inline'; document.getElementById('2011.03558v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2011.03558v1-abstract-full" style="display: none;"> The 21-cm signal from the Cosmic Dawn (CD) is likely to contain large fluctuations, with the most extreme astrophysical models on the verge of being ruled out by observations from radio interferometers. It is therefore vital that we understand not only the astrophysical processes governing this signal, but also other inherent processes impacting the signal itself, and in particular line-of-sight effects. Using our suite of fully numerical radiative transfer simulations, we investigate the impact on the redshifted 21-cm from the CD from one of these processes, namely the redshift-space distortions (RSDs). When RSDs are added, the resulting boost to the power spectra makes the signal more detectable for our models at all redshifts, further strengthening hopes that a power spectra measurement of the CD will be possible. RSDs lead to anisotropy in the signal at the beginning and end of the CD, but not while X-ray heating is underway. The inclusion of RSDs, however, decreases detectability of the non-Gaussianity of fluctuations from inhomogeneous X-ray heating measured by the skewness and kurtosis. On the other hand, mock observations created from all our simulations that include telescope noise corresponding to 1000 h observation with the Square Kilometre Array telescope show that we may be able image the CD for all heating models considered and suggest RSDs dramatically boost fluctuations coming from the inhomogeneous Ly-$伪$ background. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2011.03558v1-abstract-full').style.display = 'none'; document.getElementById('2011.03558v1-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 November, 2020; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> November 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">16 pages, 10 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/2011.01284">arXiv:2011.01284</a> <span> [<a href="https://arxiv.org/pdf/2011.01284">pdf</a>, <a href="https://arxiv.org/format/2011.01284">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Cosmology and Nongalactic Astrophysics">astro-ph.CO</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/10.1093/mnras/staa3446">10.1093/mnras/staa3446 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Comparing Foreground Removal Techniques for Recovery of the LOFAR-EoR 21cm Power Spectrum </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Hothi%2C+I">Ian Hothi</a>, <a href="/search/?searchtype=author&query=Chapman%2C+E">Emma Chapman</a>, <a href="/search/?searchtype=author&query=Pritchard%2C+J+R">Jonathan R. Pritchard</a>, <a href="/search/?searchtype=author&query=Mertens%2C+F+G">F. G. Mertens</a>, <a href="/search/?searchtype=author&query=Koopmans%2C+L+V+E">L. V. E Koopmans</a>, <a href="/search/?searchtype=author&query=Ciardi%2C+B">B. Ciardi</a>, <a href="/search/?searchtype=author&query=Gehlot%2C+B+K">B. K. Gehlot</a>, <a href="/search/?searchtype=author&query=Ghara%2C+R">R. Ghara</a>, <a href="/search/?searchtype=author&query=Ghosh%2C+A">A. Ghosh</a>, <a href="/search/?searchtype=author&query=Giri%2C+S+K">S. K. Giri</a>, <a href="/search/?searchtype=author&query=Iliev%2C+I+T">I. T. Iliev</a>, <a href="/search/?searchtype=author&query=Jeli%C4%87%2C+V">V. Jeli膰</a>, <a href="/search/?searchtype=author&query=Zaroubi%2C+S">S. Zaroubi</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="2011.01284v1-abstract-short" style="display: inline;"> We compare various foreground removal techniques that are being utilised to remove bright foregrounds in various experiments aiming to detect the redshifted 21cm signal of neutral hydrogen from the Epoch of Reionization. In this work, we test the performance of removal techniques (FastICA, GMCA, and GPR) on 10 nights of LOFAR data and investigate the possibility of recovering the latest upper limi… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2011.01284v1-abstract-full').style.display = 'inline'; document.getElementById('2011.01284v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2011.01284v1-abstract-full" style="display: none;"> We compare various foreground removal techniques that are being utilised to remove bright foregrounds in various experiments aiming to detect the redshifted 21cm signal of neutral hydrogen from the Epoch of Reionization. In this work, we test the performance of removal techniques (FastICA, GMCA, and GPR) on 10 nights of LOFAR data and investigate the possibility of recovering the latest upper limit on the 21cm signal. Interestingly, we find that GMCA and FastICA reproduce the most recent 2$蟽$ upper limit of $螖^2_{21} <$ (73)$^2$ mK$^2$ at $k=0.075~ h \mathrm{cMpc}^{-1}$, which resulted from the application of GPR. We also find that FastICA and GMCA begin to deviate from the noise-limit at \textit{k}-scales larger than $\sim 0.1 ~h \mathrm{cMpc}^{-1}$. We then replicate the data via simulations to see the source of FastICA and GMCA's limitations, by testing them against various instrumental effects. We find that no single instrumental effect, such as primary beam effects or mode-mixing, can explain the poorer recovery by FastICA and GMCA at larger \textit{k}-scales. We then test scale-independence of FastICA and GMCA, and find that lower \textit{k}-scales can be modelled by a smaller number of independent components. For larger scales ($k \gtrsim 0.1~h \mathrm{cMpc}^{-1}$), more independent components are needed to fit the foregrounds. We conclude that, the current usage of GPR by the LOFAR collaboration is the appropriate removal technique. It is both robust and less prone to overfitting, with future improvements to GPR's fitting optimisation to yield deeper limits. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2011.01284v1-abstract-full').style.display = 'none'; document.getElementById('2011.01284v1-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 November, 2020; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> November 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">15 pages, 11 figures, accepted by MNRAS on 02 November 2020</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2010.06016">arXiv:2010.06016</a> <span> [<a href="https://arxiv.org/pdf/2010.06016">pdf</a>, <a href="https://arxiv.org/format/2010.06016">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Atomic Physics">physics.atom-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/10.1039/D0FD00117A">10.1039/D0FD00117A <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Perspectives for analyzing non-linear photo ionization spectra with deep neural networks trained with synthetic Hamilton matrices </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Giri%2C+S+K">Sajal Kumar Giri</a>, <a href="/search/?searchtype=author&query=Alonso%2C+L">Lazaro Alonso</a>, <a href="/search/?searchtype=author&query=Saalmann%2C+U">Ulf Saalmann</a>, <a href="/search/?searchtype=author&query=Rost%2C+J+M">Jan Michael Rost</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="2010.06016v1-abstract-short" style="display: inline;"> We have constructed deep neural networks, which can map fluctuating photo-electron spectra obtained from noisy pulses to spectra from noise-free pulses. The network is trained on spectra from noisy pulses in combination with random Hamilton matrices, representing systems which could exist but do not necessarily exist. In [Giri et al., Phys. Rev. Lett. 124,113201 (2020)] we performed a purification… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2010.06016v1-abstract-full').style.display = 'inline'; document.getElementById('2010.06016v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2010.06016v1-abstract-full" style="display: none;"> We have constructed deep neural networks, which can map fluctuating photo-electron spectra obtained from noisy pulses to spectra from noise-free pulses. The network is trained on spectra from noisy pulses in combination with random Hamilton matrices, representing systems which could exist but do not necessarily exist. In [Giri et al., Phys. Rev. Lett. 124,113201 (2020)] we performed a purification of fluctuating spectra, that is mapping them to those from Fourier-limited Gaussian pulses. Here, we investigate the performance of such neural-network-based maps for predicting spectra of double pulses, pulses with a chirp and even partially-coherent pulses pulses from fluctuating spectra generated by noisy pulses. Secondly, we demonstrate that along with a purification of a fluctuating double-pulse spectrum, one can estimate the time-delay of the underlying double pulse, an attractive feature for single-shot spectra from SASE FELs. We demonstrate our approach with resonant two-photon ionization, a non-linear process, sensitive to details of the laser pulse. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2010.06016v1-abstract-full').style.display = 'none'; document.getElementById('2010.06016v1-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 October, 2020; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> October 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, 9 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/2006.03203">arXiv:2006.03203</a> <span> [<a href="https://arxiv.org/pdf/2006.03203">pdf</a>, <a href="https://arxiv.org/format/2006.03203">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Cosmology and Nongalactic Astrophysics">astro-ph.CO</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/10.1093/mnras/staa3593">10.1093/mnras/staa3593 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Interpreting LOFAR 21-cm signal upper limits at z~9.1 in the context of high-z galaxy and reionisation observations </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Greig%2C+B">Bradley Greig</a>, <a href="/search/?searchtype=author&query=Mesinger%2C+A">Andrei Mesinger</a>, <a href="/search/?searchtype=author&query=Koopmans%2C+L+V+E">L茅on V. E. Koopmans</a>, <a href="/search/?searchtype=author&query=Ciardi%2C+B">Benedetta Ciardi</a>, <a href="/search/?searchtype=author&query=Mellema%2C+G">Garrelt Mellema</a>, <a href="/search/?searchtype=author&query=Zaroubi%2C+S">Saleem Zaroubi</a>, <a href="/search/?searchtype=author&query=Giri%2C+S+K">Sambit K. Giri</a>, <a href="/search/?searchtype=author&query=Ghara%2C+R">Raghunath Ghara</a>, <a href="/search/?searchtype=author&query=Ghosh%2C+A">Abhik Ghosh</a>, <a href="/search/?searchtype=author&query=Iliev%2C+I+T">Ilian T. Iliev</a>, <a href="/search/?searchtype=author&query=Mertens%2C+F+G">Florent G. Mertens</a>, <a href="/search/?searchtype=author&query=Mondal%2C+R">Rajesh Mondal</a>, <a href="/search/?searchtype=author&query=Offringa%2C+A+R">Andr茅 R. Offringa</a>, <a href="/search/?searchtype=author&query=Pandey%2C+V+N">Vishambhar N. Pandey</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="2006.03203v1-abstract-short" style="display: inline;"> Using the latest upper limits on the 21-cm power spectrum at $z\approx9.1$ from the Low Frequency Array (LOFAR), we explore regions of parameter space which are inconsistent with the data. We use 21CMMC, a Monte Carlo Markov Chain sampler of 21cmFAST which directly forward models the 3D cosmic 21-cm signal in a fully Bayesian framework. We use the astrophysical parameterisation from 21cmFAST, whic… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2006.03203v1-abstract-full').style.display = 'inline'; document.getElementById('2006.03203v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2006.03203v1-abstract-full" style="display: none;"> Using the latest upper limits on the 21-cm power spectrum at $z\approx9.1$ from the Low Frequency Array (LOFAR), we explore regions of parameter space which are inconsistent with the data. We use 21CMMC, a Monte Carlo Markov Chain sampler of 21cmFAST which directly forward models the 3D cosmic 21-cm signal in a fully Bayesian framework. We use the astrophysical parameterisation from 21cmFAST, which includes mass-dependent star formation rates and ionising escape fractions as well as soft-band X-ray luminosities to place limits on the properties of the high-$z$ galaxies. Further, we connect the disfavoured regions of parameter space with existing observational constraints on the Epoch of Reionisation such as ultra-violet (UV) luminosity functions, background UV photoionisation rate, intergalactic medium (IGM) neutral fraction and the electron scattering optical depth. We find that all models exceeding the 21-cm signal limits set by LOFAR at $z\approx9.1$ are excluded at $\gtrsim2蟽$ by other probes. Finally, we place limits on the IGM spin temperature from LOFAR, disfavouring at 95 per cent confidence spin temperatures below $\sim2.6$ K across an IGM neutral fraction range of $0.15 \lesssim \bar{x}_{H{\scriptscriptstyle I}} \lesssim 0.6$. Note, these limits are only obtained from 141 hrs of data in a single redshift bin. With tighter upper limits, across multiple redshift bins expected in the near future from LOFAR, more viable models will be ruled out. Our approach demonstrates the potential of forward modelling tools such as 21CMMC in combining 21-cm observations with other high-$z$ probes to constrain the astrophysics of galaxies. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2006.03203v1-abstract-full').style.display = 'none'; document.getElementById('2006.03203v1-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> 4 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">12 pages, 4 pages, 1 table. Submitted to MNRAS, comments welcome</span> </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=Giri%2C+S+K&start=50" class="pagination-next" >Next </a> <ul class="pagination-list"> <li> <a href="/search/?searchtype=author&query=Giri%2C+S+K&start=0" class="pagination-link is-current" aria-label="Goto page 1">1 </a> </li> <li> <a href="/search/?searchtype=author&query=Giri%2C+S+K&start=50" class="pagination-link " aria-label="Page 2" aria-current="page">2 </a> </li> </ul> </nav> <div class="is-hidden-tablet">  <span class="help" style="display: inline-block;"><a href="https://github.com/arXiv/arxiv-search/releases">Search v0.5.6 released 2020-02-24</a>  </span> </div> </div> </main> <footer> <div class="columns is-desktop" role="navigation" aria-label="Secondary">  <div class="column"> <div class="columns"> 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