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arXiv 2025年

作者： Aymerich, Gaspard Kacprzak, Tomasz Refregier, Alexandre Université Paris-Saclay CNRS Institut d’Astrophysique Spatiale Orsay91405 France Université Paris-Saclay Université Paris Cité CEA CNRS AIM Gif-sur-Yvette91191 France Institute for Particle Physics and Astrophysics ETH Zurich Zurich8093 Switzerland Swiss Data Science Center Paul Scherrer Institute Villigen5232 Switzerland

Deep learning and convolutional neural networks in particular are powerful and promising tools for cosmological analysis of large-scale structure surveys. They are already providing similar performance to classical analysis methods using fixed summary statistics, are showing potential to break key degeneracies by better probe combination and will likely improve rapidly in the coming years as progress is made in the physical modelling through both software and hardware improvement. One key issue remains: unlike classical analysis, a convolutional neural network’s decision process is hidden from the user as the network optimises millions of parameters with no direct physical meaning. This prevents a clear understanding of the potential limitations and biases of the analysis, making it hard to rely on as a main analysis method. In this work, we explore the behaviour of such a convolutional neural network through a novel method. Instead of trying to analyse a network "a posteriori", i.e. after training has been completed, we study the impact on the constraining power of training the network and predicting parameters with degraded data where we removed part of the information. This allows us to gain an understanding of which parts and features of a large-scale structure survey are most important in the network’s prediction process. We find that the network’s prediction process relies on a mix of both Gaussian and non-Gaussian information, and seems to put an emphasis on structures whose scales are at the limit between linear and non-linear regimes. © 2025, CC BY.

关键词： Convolutional neural networks

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SKA sensitivity for possible radio emission from dark matter in Omega Centauri

arXiv

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arXiv 2023年

作者： Wang, Guan-Sen Chen, Zhan-Fang Zu, Lei Gong, Hao Feng, Lei Fan, Yi-Zhong Key Laboratory of Dark Matter and Space Astronomy Purple Mountain Observatory Chinese Academy of Sciences Nanjing210023 China School of Astronomy and Space Science University of Science and Technology of China Hefei Anhui230026 China School of Mathematics and Physics Bengbu University Bengbu Anhui233030 China Joint Center for Particle Nuclear Physics and Cosmology Nanjing University-Purple Mountain Observatory Nanjing210093 China

Omega Centauri, the largest known globular cluster in the Milky Way, is believed to be the remains of a dwarf galaxy's core. Giving its potential abundance of dark matter (DM), it is an attractive target for investigating the nature of this elusive substance in our local environment. Our study demonstrates that by observing Omega Centauri with the SKA for 100 hours, we can detect synchrotron radio or Inverse Compton (IC) emissions from the DM annihilation products. It enables us to constrain the cross-section of DM annihilation down to ∼ 10-30cm3s-1for DM mass from several GeV to 100 GeV, which is much stronger compared with other observations. Additionally, we explore the axion, another well-motivated DM candidate, and provide stimulated decay calculations. It turns out that the sensitivity can reach gaγγ ∼ 10-10GeV-1for 2×10-7eV -4eV. Copyright © 2023, The Authors. All rights reserved.

关键词： Dark Matter

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Fitting very flexible models: Linear regression with large numbers of parameters

arXiv

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arXiv 2021年

作者： Hogg, David W. Villar, Soledad Flatiron Institute Center for Cosmology and Particle Physics Department of Physics New York University Center for Data Science New York University Max-Planck-Institut für Astronomie Heidelberg United States Department of Applied Mathematics & Statistics Johns Hopkins University Mathematical Institute for Data Science Johns Hopkins University United States

There are many uses for linear fitting;the context here is interpolation and denoising of data, as when you have calibration data and you want to fit a smooth, flexible function to those data. Or you want to fit a flexible function to de-trend a time series or normalize a spectrum. In these contexts, investigators often choose a polynomial basis, or a Fourier basis, or wavelets, or something equally general. They also choose an order, or number of basis functions to fit, and (often) some kind of regularization. We discuss how this basis-function fitting is done, with ordinary least squares and extensions thereof. We emphasize that it is often valuable to choose far more parameters than data points, despite folk rules to the contrary: Suitably regularized models with enormous numbers of parameters generalize well and make good predictions for held-out data;over-fitting is not (mainly) a problem of having too many parameters. It is even possible to take the limit of infinite parameters, at which, if the basis and regularization are chosen correctly, the least-squares fit becomes the mean of a Gaussian process. We recommend cross-validation as a good empirical method for model selection (for example, setting the number of parameters and the form of the regularization), and jackknife resampling as a good empirical method for estimating the uncertainties of the predictions made by the model. We also give advice for building stable computational implementations. Copyright © 2021, The Authors. All rights reserved.

关键词： Functions

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Cosmological perturbations in the energy-momentum squared gravity theory:constraints from gravitational wave standard sirens and redshift space distortions

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Chinese physics C 2025年第4期 202-211页

作者：付启铭张鑫 Institute of Physics Shaanxi University of Technology Lanzhou Center for Theoretical Physics Key Laboratory of Theoretical Physics of Gansu Provinceand Key Laboratory of Quantum Theory andApplications of MoELanzhou University Key Laboratory of Cosmology and Astrophysics (Liaoning) & College of Sciences Northeastern University Key Laboratory of Data Analytics and Optimization for Smart Industry (Ministry of Education) Northeastern University National Frontiers Science Center for Industrial Intelligence and Systems Optimization Northeastern University

We investigate the linear cosmological perturbations in the context of the so-called energy-momentum squared gravity(EMSG) *** research shows that the EMSG theory can reproduce a viable background cosmological evolution comparable to ΛCDM,whereas the matter-dominated era exhibits slight *** this paper,we focus on power-law EMSG models and derive the equations for the linear cosmological *** explore the propagation of the gravitational wave(GW) and the growth of matter density perturbation at the first order,and we estimate the model parameters from the simulated GW and observed redshift space distortion *** analysis reveals that the model parameters should be small and positive in the 1 σ confidence interval,which indicates that the theory agrees closely with the observational data and can be considered an alternative to the standard cosmological model.

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Pre-Merger Detection and Characterization of Inspiraling Binary Neutron Stars Derived from Neural Posterior Estimation

arXiv

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arXiv 2024年

作者： van Straalen, Wouter Kolmus, Alex Janquart, Justin Van Den Broeck, Chris Department of Physics Utrecht University Princetonplein 1 Utrecht3584 CC Netherlands Radboud University Nijmegen Toernooiveld 212 Nijmegen6525 EC Netherlands Nikhef Science Park 105 Amsterdam1098 XG Netherlands Center for Cosmology Particle Physics and Phenomenology - CP3 Université Catholique de Louvain Louvain-la-NeuveB-1348 Belgium Royal Observatory of Belgium Avenue Circulaire 3 Uccle1180 Belgium

As the sensitivity of the international gravitational wave detector network increases, observing binary neutron star signals will become more common. Moreover, since these signals will be louder, the chances of detecting them before their mergers increase. However, this requires an efficient framework. In this work, we present a machine-learning-based framework capable of detecting and analyzing binary neutron star mergers during their inspiral. Using a residual network to summarize the strain data, we use its output as input to a classifier giving the probability of having a signal in the data, and to a normalizing-flow network to perform neural posterior estimation. We train a network for several maximum frequencies reached by the signal to improve the estimate over time. Our framework shows good results both for detection and characterization, with improved parameter estimation as we get closer to the merger time. Thus, we can effectively evolve the precision of the sky location as the merger draws closer. Such a setup would be important for future multi-messenger searches where one would like to have the most precise information possible, as early as possible. Copyright © 2024, The Authors. All rights reserved.

关键词： Gravity waves

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Holographic screen sequestration

arXiv

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arXiv 2023年

作者： Chatwin-Davies, Aidan Leung, Pompey Remmen, Grant N. Okinawa Institute of Science and Technology 1919-1 Tancha Onna-son Kunigami-gun Okinawa904-0495 Japan Department of Physics and Astronomy University of British Columbia 6224 Agricultural Road VancouverBCV6T 1Z1 Canada Center for Cosmology and Particle Physics Department of Physics New York University New YorkNY10003 United States

Holographic screens are codimension-one hypersurfaces that extend the notion of apparent horizons to general (non-black hole) spacetimes and that display interesting thermodynamic properties. We show that if a spacetime contains a codimension-two, boundary-homologous, minimal extremal spacelike surface X (known as an HRT surface in AdS/CFT), then any holographic screens are sequestered to the causal wedges of X. That is, any single connected component of a holographic screen can be located in at most one of the causal future, causal past, inner wedge, or outer wedge of X. We comment on how this result informs possible coarse grained entropic interpretations of generic holographic screens, as well as on connections to semiclassical objects such as quantum extremal surfaces. Copyright © 2023, The Authors. All rights reserved.

关键词： Holography

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Measurement of the photometric Baryon Acoustic Oscillations with self-calibrated redshift distribution

arXiv

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arXiv 2024年

作者： Song, Ruiyu Chan, Kwan Chuen Xu, Haojie Zheng, Weilun School of Physics and Astronomy Sun Yat-Sen University 2 Daxue Road Tangjia Zhuhai519082 China CSST Science Center for the Guangdong-Hongkong-Macau Greater Bay Area SYSU Zhuhai519082 China Shanghai Astronomical Observatory Chinese Academy of Sciences Nandan Road 80 Shanghai200240 China Department of Astronomy Shanghai Jiao Tong University Shanghai200240 China Shanghai Key Laboratory for Particle Physics and Cosmology China

We use a galaxy sample derived from the DECaLS DR9 to measure the Baryonic Acoustic Oscillations (BAO). The magnitude-limited sample consists of 10.6 million galaxies in an area of 4974 deg2 over the redshift range of [0.6, 1]. A key novelty of this work is that the true redshift distribution of the photo-z sample is derived from the self calibration method, which determines the true redshift distribution using the clustering information of the photometric data alone. Through the angular correlation function in four tomographic bins, we constrain the BAO scale dilation parameter α to be 1.025 ± 0.033, consistent with the fiducial Planck cosmology. Alternatively, the ratio between the comoving angular diameter distance and the sound horizon, DM/rs is constrained to be 18.94 ± 0.61 at the effective redshift of 0.749. We corroborate our results with the true redshift distribution obtained from a weighted spectroscopic sample, finding very good agreement. We have conducted a series of tests to demonstrate the robustness of the measurement. Our work demonstrates that the self calibration method can effectively constrain the true redshift distribution in cosmological applications, especially in the context of photometric BAO measurement. Copyright © 2024, The Authors. All rights reserved.

关键词： Galaxies

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Upper Bound on Thermal Gravitational Wave Backgrounds from Hidden Sectors

arXiv

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arXiv 2023年

作者： Drewes, Marco Georis, Yannis Klaric, Juraj Klose, Philipp Centre for Cosmology Particle Physics and Phenomenology Université Catholique de Louvain Louvain-la-NeuveB-1348 Belgium Institute for Theoretical Physics Amsterdam Delta Institute for Theoretical Physics University of Amsterdam Science Park 904 Amsterdam1098 XH Netherlands Nikhef Theory Group Science Park 105 Amsterdam1098 XG Netherlands University of Zagreb Faculty of Science Department of Physics Zagreb10000 Croatia Institute for Theoretical Physics Albert Einstein Center for Fundamental Physics University of Bern Switzerland Fakultät für Physik Universität Bielefeld Germany

Hot viscous plasmas unavoidably emit a gravitational wave background, similar to electromagnetic black body radiation. We study the contribution from hidden particles to the diffuse background emitted by the primordial plasma in the early universe. While this contribution can easily dominate over that from Standard Model particles, we find that both are capped by a generic upper bound that makes them difficult to detect with interferometers in the foreseeable future. We illustrate our results for axion-like particles and heavy neutral leptons. Finally, our results suggest that previous works overestimated the gravitational wave background from particle decays out of thermal equilibrium. Copyright © 2023, The Authors. All rights reserved.

关键词： Gravitational effects

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Towards an Effective String Theory for the flux tube

arXiv

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arXiv 2024年

作者： Athenodorou, Andreas Dubovsky, Sergei Luo, Conghuan Teper, Michael Computation-based Science and Technology Research Center The Cyprus Institute Cyprus Center for Cosmology and Particle Physics Department of Physics New York University New YorkNY10003 United States Institute for Advanced Study PrincetonNJ08540 United States Department of Physics and Astronomy University of Southern California Los AngelesCA90089 United States Rudolf Peierls Centre for Theoretical Physics University of Oxford Parks Road OxfordOX1 3PU United Kingdom All Souls College University of Oxford High Street OxfordOX1 4AL United Kingdom

The quest to develop an effective string theory capable of describing the confining flux tube has been a longstanding objective within the theoretical physics community. Recent lattice results indicate that the low-lying spectrum of the flux tube in both three and four dimensions can be partially described by the Nambu-Goto string with minor deviations. However, several excitation states exhibit significant corrections that have remained unexplained until recently. Recent advancements suggest that a Thermodynamic Bethe Ansatz (TBA) analysis, expanded in both 1/R√σ and the softness of phonons i.e. p/√σ, can lead to a robust effective string theory for the flux-tube with length R. Furthermore, lattice data points to the existence of an axion field on the world-sheet of the flux-tube, implying that an Axionic String Ansatz (ASA) should accompany the Nambu-Goto framework. We will provide compelling evidence in these proceedings that this approach can closely approximate the flux tube data. We will demonstrate this by comparing results obtained for the spectrum of the closed SU(Nc) flux-tube extracted using lattice techniques in four dimensions. © 2024, CC BY-NC-ND.

关键词： String theory

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β-decay half-lives of the r-process waiting-point isotones of N=81 and 82 nuclei

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Physical Review C 2023年第3期107卷 034316-034316页

作者： C. Ma Y. Lu Y. Lei Y. M. Zhao Shanghai Key Laboratory of Particle Physics and Cosmology School of Physics and Astronomy Shanghai Jiao Tong University Shanghai 200240 China College of Physics and Engineering Qufu Normal University Qufu 273165 China School of National Defense Science and Technology Southwest University of Science and Technology Mianyang 621010 China Collaborative Innovation Center of IFSA (CICIFSA) Shanghai Jiao Tong University Shanghai 200240 China

In this paper we perform systematic calculations of β-decay half-lives for the r-process waiting-point isotones of N=81 and 82, in the framework of nucleon-pair approximation. A phenomenological form of the Hamiltonian, which includes single-particle energies, pairing plus quadrupole interactions, and Gamow-Teller interactions is assumed, and the theoretical β-decay energies are taken based on the Bayesian machine learning. A good agreement with experimental values of half-lives is achieved by using the nucleon-pair truncated model space in which the S-pair condensation dominates. Our calculated half-lives are found to be very sensitive to β-decay energies on the one hand, and are quite robust with respect to extension of the model space and variation of interaction parameters on the other hand.

关键词： Beta decay Binding energy & masses Collective levels Energy levels & level densities Shell model 90 ≤ A ≤ 149

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