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arXiv 2025年

作者： Icaza-Lizaola, M. Sirks, E.L. Song, Yong-Seon Norberg, Peder Shi, Feng Korea Astronomy and Space Science Institute 776 Daedeok-daero Yuseong-gu Daejeon34055 Korea Republic of Departamento de Física Teórica Facultad de Ciencias M-8 Universidad Autónoma de Madrid Madrid28049 Spain Facultad de Ciencias Universidad Autónoma de Madrid Madrid28049 Spain School of Physics The University of Sydney SydneyNSW2006 Australia The Australian Research Council Centre of Excellence for Dark Matter Particle Physics Australia Institute for Computational Cosmology Department of Physics Durham University South Road DurhamDH1 3LE United Kingdom Institute for Data Science Department of Physics Durham University South Road DurhamDH1 3LE United Kingdom Centre for Extragalactic Astronomy Department of Physics Durham University South Road DurhamDH1 3LE United Kingdom School of Aerospace Science and Technology Xidian University Xi’an710126 China

The analysis of state-of-the-art cosmological surveys like the Dark Energy Spectroscopic Instrument (DESI) survey requires high-resolution, large-volume simulations. However, the computational cost of hydrodynamical simulations at these scales is prohibitive. Instead, dark matter (DM)-only simulations are used, with galaxies populated a posteriori, typically via halo occupation distribution (HOD) models. While effective, HOD models are statistical in nature and lack full physical motivation. In this work, we explore using neural networks (NNs) to learn the complex, physically motivated relationships between DM haloes and galaxy properties. Trained on small-volume, high-resolution hydrodynamical simulations, our NN predicts galaxy properties in a larger DM-only simulation and determines which galaxies should be classified as luminous red galaxies (LRGs). Comparing the original LRG sample to the one generated by our NN, we find that, while the subhalo mass distributions are similar, our NN selects fewer low-mass subhaloes as LRG hosts, possibly due to the absence of baryonic feedback effects in DM-only simulations. This feedback could brighten or redden galaxies, altering their classification. Finally, we generate a new LRG sample by fitting an HOD model to the NN-generated LRG sample. We verify that both the HOD- and NN-generated samples preserve a set of bias parameter relations, which assume that the higher-order parameters, ｂｓ2 and ｂ3nl, are determined by the linear bias parameter ｂ1. These relations are commonly used to simplify clustering analyses. © 2025, CC BY.

关键词： Dark Matter

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GW190521: Tracing imprints of spin-precession on the most massive black hole binary

arXiv

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arXiv 2023年

作者： Miller, Simona J. Isi, Maximiliano Chatziioannou, Katerina Varma, Vijay Mandel, Ilya Department of Physics California Institute of Technology PasadenaCA91125 United States LIGO Laboratory California Institute of Technology PasadenaCA91125 United States Center for Computational Astrophysics Flatiron Institute New YorkNY10010 United States Department of Mathematics Center for Scientific Computing and Data Science Research University of Massachusetts DartmouthMA02747 United States Max Planck Institute for Gravitational Physics Albert Einstein Institute PotsdamD-14476 Germany School of Physics Astronomy Monash University ClaytonVIC3800 Australia OzGrav: The ARC Centre of Excellence for Gravitational Wave Discovery ClaytonVIC3800 Australia

GW190521 is a remarkable gravitational-wave signal on multiple fronts: its source is the most massive black hole binary identified to date and could have spins misaligned with its orbit, leading to spin-induced precession;an astrophysically consequential property linked to the binary's origin. However, due to its large mass, GW190521 was only observed during its final 3-4 cycles, making precession constraints puzzling and giving rise to alternative interpretations, such as eccentricity. Motivated by these complications, we trace the observational imprints of precession on GW190521 by dissecting the data with a novel time domain technique, allowing us to explore the morphology and interplay of the few observed cycles. We find that precession inference hinges on a quiet portion of the pre-merger data that is suppressed relative to the merger-ringdown. Neither pre-merger nor post-merger data alone are the sole driver of inference, but rather their combination;in the quasi-circular scenario, precession emerges as a mechanism to accommodate the lack of a stronger pre-merger signal in light of the observed post-merger. In terms of source dynamics, the pre-merger suppression arises from a tilting of the binary with respect to the observer. Establishing such a consistent picture between the source dynamics and the observed data is crucial for characterizing the growing number of massive binary observations and bolstering the robustness of ensuing astrophysical claims. © 2023, CC BY.

关键词： Stars

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Evolutionary dynamics of any multiplayer game on regular graphs

arXiv

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arXiv 2024年

作者： Wang, Chaoqian Perc, Matjaž Szolnoki, Attila Department of Computational and Data Sciences George Mason University FairfaxVA22030 United States Faculty of Natural Sciences and Mathematics University of Maribor Koroška cesta 160 Maribor2000 Slovenia Community Healthcare Center Dr. Adolf Drolc Maribor Vošnjakova ulica 2 Maribor2000 Slovenia Complexity Science Hub Vienna Josefstädterstraße 39 Vienna1080 Austria Department of Physics Kyung Hee University 26 Kyungheedae-ro Dongdaemun-gu Seoul Korea Republic of Institute of Technical Physics and Materials Science Centre for Energy Research P.O. Box 49 BudapestH-1525 Hungary

Multiplayer games on graphs are at the heart of theoretical descriptions of key evolutionary processes that govern vital social and natural systems. However, a comprehensive theoretical framework for solving multiplayer games with an arbitrary number of strategies on graphs is still missing. Here, we solve this by drawing an analogy with the Balls-and-Boxes problem, based on which we show that the local configuration of multiplayer games on graphs is equivalent to distributing k identical co-players among n distinct strategies. We use this to derive the replicator equation for any n-strategy multiplayer game under weak selection, which can be solved in polynomial time. As an example, we revisit the second-order free-riding problem, where costly punishment cannot truly resolve social dilemmas in a well-mixed population. Yet, in structured populations, we derive an accurate threshold for the punishment strength, beyond which punishment can either lead to the extinction of defection or transform the system into a rock-paper-scissors-like cycle. The analytical solution also qualitatively agrees with the phase diagrams that were previously obtained for non-marginal selection strengths. Our framework thus allows an exploration of any multi-strategy multiplayer game on regular graphs. © 2024, CC BY.

关键词： Graphic methods

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High precision calculation of the hadronic vacuum polarisation contribution to the muon anomaly

arXiv

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arXiv 2024年

作者： Boccaletti, A. Borsanyi, Sz. Davier, M. Fodor, Z. Frech, F. Gérardin, A. Giusti, D. Kotov, A.Yu. Lellouch, L. Lippert, Th. Lupo, A. Malaescu, B. Mutzel, S. Portelli, A. Risch, A. Sjö, M. Stokes, F. Szabo, K.K. Toth, B.C. Wang, G. Zhang, Z. Department of Physics University of Wuppertal WuppertalD-42119 Germany Jülich Supercomputing Centre Forschungszentrum Jülich JülichD-52428 Germany IJCLab Université Paris-Saclay CNRS IN2P3 Orsay91405 France Physics Department Pennsylvania State University University ParkPA16802 United States Institute for Computational and Data Sciences Pennsylvania State University University ParkPA16802 United States Institute for Theoretical Physics Eötvös University BudapestH-1117 Hungary University of California 9500 Gilman Drive La Jolla San DiegoCA92093 United States Aix Marseille Univ Université de Toulon CNRS CPT IPhU Marseille France Fakultät für Physik Universität Regensburg Regensburg93040 Germany LPNHE Sorbonne Université Université Paris Cité CNRS IN2P3 Paris75252 France Laboratoire de Physique de l'Ecole Normale Supérieure Mines Paris - PSL CNRS Inria PSL Research University Paris France School of Physics and Astronomy University of Edinburgh EdinburghEH9 3JZ United Kingdom RIKEN Center for Computational Science Kobe650-0047 Japan Special Research Centre for the Subatomic Structure of Matter Department of Physics University of Adelaide SA5005 Australia

For fifty years, the standard model of particle physics has been hugely successful in describing subatomic phenomena. Recently, this statement appeared to be contradicted by the strong disagreement between measurements of the anomalous magnetic moment of the muon [1], aµ, and the reference standard-model prediction [2]. Such a large discrepancy should signal the discovery of interactions or particles not present in the standard model. However, two independent determinations [3, 4] of the most uncertain contribution to the standard-model prediction display significantly less tension with the measurement. Here we present a new first-principle calculation of this contribution. We reduce uncertainties compared to our earlier computation [3] by 40%. To reach this unprecedented level of precision we improve on many aspects of the calculation. Namely, we perform large-scale lattice QCD simulations on finer lattices than in Ref. [3], allowing for an even more accurate continuum extrapolation. We also include a small, long-distance contribution obtained using input from experiments in a low-energy regime where they all agree. Combined with the extensive calculations of other standard model contributions summarised in Ref. [2], our result leads to a prediction that differs from the measurement of aµ by only 0.9 standard deviations. This provides a remarkable validation of the standard model to 0.37ppm. Copyright © 2024, The Authors. All rights reserved.

关键词： Forecasting

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Reflection-asymmetric wormholes and their double shadows

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Physical Review D 2020年第8期102卷 084044-084044页

作者： Maciek Wielgus Jiří Horák Frederic Vincent Marek Abramowicz Nicolaus Copernicus Astronomical Centre Polish Academy of Sciences Bartycka 18 00-716 Warsaw Poland Research Center for Computational Physics and Data Processing Institute of Physics Silesian University in Opava Bezručovo náměstí 1150/13746 01 Opava Czech Republic and Department of Physics Göteborg University 412-96 Göteborg Sweden

We discuss construction and observational properties of wormholes obtained by connecting two Reissner-Nordström spacetimes with distinct mass and charge parameters. These objects are spherically symmetric, but not reflection symmetric, as the connected spacetimes differ. The reflection-asymmetric wormholes may reflect a significant fraction of the infalling radiation back to the spacetime of its origin. We interpret this effect in a simple framework of the effective photon potential. Depending on the model parameters, image of such a wormhole seen by a distant observer (its “shadow”) may contain a photon ring formed on the observer’s side, photon ring formed on the other side of the wormhole, or both photon rings. These unique topological features would allow us to firmly distinguish this class of objects from Kerr black holes using radioastronomical observations.

关键词： Classical black holes General relativity General relativity equations & solutions Radio, microwave, & sub-mm astronomy

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Barrow and Tsallis entropies after the DESI DR2 BAO data

arXiv

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arXiv 2025年

作者： Luciano, Giuseppe Gaetano Paliathanasis, Andronikos Saridakis, Emmanuel N. Department of Chemistry Physics and Environmental and Soil Sciences Escola Politecnica Superior Universidad de Lleida Av. Jaume II 69 Lleida25001 Spain School for Data Science and Computational Thinking Stellenbosch University 44 Banghoek Rd Stellenbosch7600 South Africa Centre for Space Research North-West University Potchefstroom2520 South Africa Departamento de Matemàticas Universidad Catòlica del Norte Avda. Angamos 0610 Casilla Antofagasta1280 Chile National Observatory of Athens Lofos Nymfon 11852 Greece CAS Key Laboratory for Research in Galaxies and Cosmology School of Astronomy and Space Science University of Science and Technology of China Hefei230026 China Departamento de Matemáticas Universidad Católica del Norte Avda. Angamos 0610 Casilla Antofagasta1280 Chile

Modified cosmology based on Barrow entropy arises from the gravity–thermodynamics conjecture, in which the standard Bekenstein–Hawking entropy is replaced by the Barrow entropy of quantum-gravitational origin, characterized by the Barrow parameter ∆. Interestingly, this framework exhibits similarities with cosmology based on Tsallis δ-entropy, which, although rooted in a non-extensive generalization of Boltzmann–Gibbs statistics, features the same power-law deformation of the holographic scaling present in the Barrow case. We use observational data from Supernova Type Ia (SNIa), Cosmic Chronometers (CC), and Baryonic acoustic oscillations (BAO), including the recently released DESI DR2 data, in order to extract constraints on such scenarios. As we show, the best-fit value for the Barrow exponent ∆ is found to be negative, while the zero value, which corresponds to ΛCDM paradigm, is allowed only in the range of 2σ for three out of four datasets. Additionally, for the case of the SN0+OHD+BAO dataset, for the current Hubble function we obtain a value of H0 = 72.2+0−0.99, which offers an alleviation for the H0 tension. Finally, by applying information criteria such as the Akaike Information Criterion and the Bayes evidence, we compare the fitting efficiency of the scenario at hand with ΛCDM cosmology, showing that the latter is slightly favoured. © 2025, CC BY.

关键词： Dark Matter

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Stable attractors in the three-dimensional general relativistic Poynting-Robertson effect

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Physical Review D 2020年第2期101卷 024025-024025页

作者： Vittorio De Falco Pavel Bakala Research Centre for Computational Physics and Data Processing Faculty of Philosophy & Science Silesian University in Opava Bezručovo namesti 13 CZ-746 01 Opava Czech Republic M. R. Štefánik Observatory and Planetarium Sládkovičova 41 920 01 Hlohovec Slovak Republic

We prove the stability of the critical hypersurfaces associated with the three-dimensional general relativistic Poynting-Robertson effect. The equatorial ring configures to be as a stable attractor and the whole critical hypersurface as a basin of attraction for this dynamical system. We introduce a new, simpler (in terms of calculations), and more physical approach within the Lyapunov theory. We propose three different Lyapunov functions, each one carrying important information and very useful for understanding such phenomenon under different aspects.

关键词： General relativity General relativity equations & solutions Gravitation Numerical simulations in gravitation & astrophysics

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Beam-Plasma Dynamics in Finite-Length, Collisionless Inhomogeneous Systems

arXiv

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arXiv 2021年

作者： Mishra, R. Moulick, R. Adhikari, S. Marholm, S. Eklund, A.J. Miloch, W.J. Department of Physics University of Oslo PO Box 1048 Blindern OsloNO-0316 Norway Centre of Plasma Physics Institute for Plasma Research Nazirakhat Assam Sonapur782402 India Homi Bhaba National Institute Training School Complex Anushaktinagar Mumbai400094 India Department of Computational Materials Processing Institute for Energy Technology Instituttveien 8 Kjeller2007 Norway Materials Physics Oslo SINTEF Industry Forskningsveien 1 OsloNO-0373 Norway

This study investigates the streaming instability triggered by ion motion in a plasma system that is finite in length, collisionless, and inhomogeneous. Employing numerical simulations using Particle-In-Cell (PIC) techniques and kinetic equations, the study examines how inhomogeneity emerges from integrating a cold ion beam with a background plasma within a confined system. The findings suggest that steady ion flow can modify ion sound waves through acoustic reflections from system boundaries, leading to instability. Such phenomena are known to be a hydrodynamic effect. However, there are also signatures of the beam-driven ion sound instability where kinetic resonances play a pivotal role. The main objective is to understand the impact of a finite-length system on beam-plasma instability and to identify the wave modes supported in such *** Codes 76X05, 76E20, 85-10, 82D10 Copyright © 2021, The Authors. All rights reserved.

关键词： Plasma stability

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GRAVITATIONAL SELF-LENSING OF FAST RADIO BURSTS IN NEUTRON STAR MAGNETOSPHERES: I. THE MODEL

arXiv

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arXiv 2024年

作者： Dall'Osso, Simone La Placa, Riccardo Stella, Luigi Bakala, Pavel Possenti, Andrea Istituto Nazionale di Fisica Nucleare - Roma 1 Piazzale Aldo Moro 2 Roma00185 Italy GSC - Goethe University of Frankfurt Max von Laue Strasse 1 Frankfurt Germany Dipartimento di Fisica Università La Sapienza Piazzale Aldo Moro 5 Roma00185 Italy INAF - Osservatorio Astronomico di Roma via Frascati 33 Monte Porzio CatoneI-00078 Italy Dipartimento di Fisica Università di Roma "Tor Vergata" Via della Ricerca Scientifica Roma00133 Italy Research Centre for Computational Physics and Data Processing Silesian University in Opava Bezručovo nám. 13 OpavaCZ-74601 Czech Republic M. R. Štefánik Observatory and Planetarium Sládkovičova 41 Hlohovec920 01 Slovakia INAF Osservatorio Astronomico di Cagliari Via della Scienza 5 Selargius09047 Italy

Fast Radio Bursts (FRBs) are cosmological sub-second bursts of coherent radio emission, whose source is still unknown. To date, the galactic magnetar SGR 1935+2154 is the only astrophysical object known to emit radio bursts akin to FRBs, albeit less powerful, supporting suggestions that FRBs originate from magnetars. Many remarkable properties of FRBs, e.g. the dichotomy between repeaters and one-off sources, and their power-law energy distributions (with typical index ∼ 2 − 3), are not well understood yet. Moreover, the huge radio power released by the most active repeaters is challenging even for the magnetic energy reservoir of magnetars. Here we assume that FRBs originate from co-rotating hot-spots anchored in neutron star magnetospheres and get occasionally amplified by large factors via gravitational self-lensing in the strong NS field. We evaluate the probability of amplification and show that (i) a power-law energy distribution of events ∝ E− (2−3) is generally expected, (ii) all FRB sources may be regarded as repeating, their appearance as one-off sources or repeaters being determined by the critical dependence of the amplification probability on the emission geometry and source orientation relative to Earth and (iii) the most active repeaters, in particular, correspond to extremely rare and finely-tuned orientations (∼ one in 106), leading to large probabilities of amplification which make their bursts frequently detectable. At the same time, their power release appears enhanced, typically by factors 10, easing their energy budget problem. © 2024, CC BY-SA.

关键词： Budget control

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Trapping of null geodesics in slowly rotating spacetimes

arXiv

引用

arXiv 2020年

作者： Vrba, Jaroslav Urbanec, Martin Stuchlík, Zdeněk Miller, John C. Research Centre for Theoretical Physics and Astrophysics Institute of Physics in Opava Silesian University in Opava Bezručovo náměstí 13 OpavaCZ-74601 Czech Republic Research Centre for Computational Physics and Data Processing Institute of Physics in Opava Silesian University in Opava Bezručovo náměstí 13 OpavaCZ-74601 Czech Republic University of Oxford Keble Road OxfordOX1 3RH United Kingdom

Extremely compact objects containing a region of trapped null geodesics could be of astrophysical relevance due to trapping of neutrinos with consequent impact on cooling processes or trapping of gravitational waves. These objects have previously been studied under the assumption of spherical symmetry. In the present paper, we consider a simple generalization by studying trapping of null geodesics in the framework of the Hartle-Thorne slow-rotation approximation taken to first order in the angular velocity, and considering a uniform-density object with uniform emissivity for the null geodesics. We calculate effective potentials and escape cones for the null geodesics and how they depend on the parameters of the spacetimes, and also calculate the "local" and "global" coefficients of efficiency for the trapping. We demonstrate that due to the rotation the trapping efficiency is different for co-rotating and retrograde null geodesics, and that trapping can occur even for R > 3GM/c2, contrary to what happens in the absence of rotation. Copyright © 2020, The Authors. All rights reserved.

关键词： Efficiency

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