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arXiv 2021年

作者： Lecoanet, Daniel Cantiello, Matteo Anders, Evan H. Quataert, Eliot Couston, Louis-Alexandre Bouffard, Mathieu Favier, Benjamin Le Bars, Michael Department of Engineering Sciences and Applied Mathematics Northwestern University EvanstonIL60208 United States CIERA Northwestern University EvanstonIL60201 United States Center for Computational Astrophysics Flatiron Institute New YorkNY10010 United States Department of Astrophysical Sciences Princeton Univesity PrincetonNJ08544 United States Univ Lyon ENS de Lyon Univ Claude Bernard CNRS Laboratoire de Physique LyonF-69342 France Aix Marseille Université CNRS Centrale Marseille IRPHE Marseille France

Recent photometric observations of massive stars show ubiquitous low-frequency "red-noise" variability, which has been interpreted as internal gravity waves (IGWs). Simulations of IGWs generated by convection show smooth surface wave spectra, qualitatively matching the observed red-noise. On the other hand, theoretical calculations by Shiode et al (2013) and Lecoanet et al (2019) predict IGWs should manifest at the surface as regularly-spaced peaks associated with standing g-modes. In this work, we compare these theoretical approaches to simplified 2D numerical simulations. The simulations show g-mode peaks at their surface, and are in good agreement with Lecoanet et al (2019). The amplitude estimates of Shiode et al (2013) did not take into account the finite width of the g-mode peaks;after correcting for this finite width, we find good agreement with simulations. However, simulations need to be run for hundreds of convection turnover times for the peaks to become visible;this is a long time to run a simulation, but a short time in the life of a star. The final spectrum can be predicted by calculating the wave energy flux spectrum in much shorter simulations, and then either applying the theory of Shiode et al (2013) or Lecoanet et al (2019). Copyright © 2021, The Authors. All rights reserved.

关键词： Surface waves

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DPA-2:a large atomic model as a multitask learner

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npj computational Materials 2024年第1期10卷 185-199页

作者： Duo Zhang Xinzijian Liu Xiangyu Zhang Chengqian Zhang Chun Cai Hangrui Bi Yiming Du Xuejian Qin Anyang Peng Jiameng Huang Bowen Li Yifan Shan Jinzhe Zeng Yuzhi Zhang Siyuan Liu Yifan Li Junhan Chang Xinyan Wang Shuo Zhou Jianchuan Liu Xiaoshan Luo Zhenyu Wang Wanrun Jiang Jing Wu Yudi Yang Jiyuan Yang Manyi Yang Fu-Qiang Gong Linshuang Zhang Mengchao Shi Fu-Zhi Dai Darrin M.York Shi Liu Tong Zhu Zhicheng Zhong Jian Lv Jun Cheng Weile Jia Mohan Chen Guolin Ke Weinan E Linfeng Zhang Han Wang AI for Science Institute BeijingP.R.China DP Technology BeijingP.R.China Academy for Advanced Interdisciplinary Studies Peking UniversityBeijingP.R.China State Key Lab of Processors Institute of Computing TechnologyChinese Academy of SciencesBeijingP.R.China University of Chinese Academy of Sciences BeijingP.R.China HEDPS CAPTCollege of EngineeringPeking UniversityBeijingP.R.China Ningbo Institute of Materials Technology and Engineering Chinese Academy of SciencesNingboP.R.China CAS Key Laboratory of Magnetic Materials and Devices and Zhejiang Province Key Laboratory of Magnetic Materials and Application Technology Chinese Academy of SciencesNingboP.R.China School of Electronics Engineering and Computer Science Peking UniversityBeijingP.R.China Shanghai Engineering Research Center of Molecular Therapeutics&New Drug Development School of Chemistry and Molecular EngineeringEast China Normal UniversityShanghaiP.R.China Laboratory for Biomolecular Simulation Research Institute for Quantitative Biomedicine and Department of Chemistry and Chemical BiologyRutgers UniversityPiscatawayNJUSA Department of Chemistry Princeton UniversityPrincetonNJUSA College of Chemistry and Molecular Engineering Peking UniversityBeijingP.R.China Yuanpei College Peking UniversityBeijingP.R.China School of Electrical Engineering and Electronic Information Xihua UniversityChengduP.R.China State Key Laboratory of Superhard Materials College of PhysicsJilin UniversityChangchunP.R.China Key Laboratory of Material Simulation Methods&Software of Ministry of Education College of PhysicsJilin UniversityChangchunP.R.China International Center of Future Science Jilin UniversityChangchunP.R.China Key Laboratory for Quantum Materialsof Zhejiang Province Department of PhysicsSchool of ScienceWestlake UniversityHangzhouP.R.China Atomistic Simulations Italian Institute of TechnologyGenovaItaly State Key Laboratory of Physical Chemistry of Solid Surface iChEMCollege of Chemistry and Chemical EngineeringXiame

The rapid advancements in artificial intelligence(AI)are catalyzing transformative changes in atomic modeling,simulation,and ***-driven potential energy models havedemonstrated the capability to conduct large-scale,long-duration simulations with the accuracy of ab initio electronic structure ***,the model generation process remains a bottleneck for large-scale *** propose a shift towards a model-centric ecosystem,wherein a large atomic model(LAM),pretrained across multiple disciplines,can be efficiently fine-tuned and distilled for various downstream tasks,thereby establishing a new framework for molecular *** this study,we introduce the DPA-2 architecture as a prototype for ***-trained on a diverse array of chemical and materials systemsusing a multi-task approach,DPA-2demonstrates superior generalization capabilities across multiple downstream tasks compared to the traditional single-task pre-training and fine-tuning *** approach sets the stage for the development and broad application of LAMs in molecular and materials simulation research.

关键词： DPA establishing thereby

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Interacting dark sector within ETHOS: Cosmological constraints from SPT cluster abundance with DES and HST weak lensing data

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Physical Review D 2025年第8期111卷 083543-083543页

作者： A. Mazoun S. Bocquet J. J. Mohr M. Garny H. Rubira M. Klein L. E. Bleem S. Grandis T. Schrabback M. Aguena S. Allam S. W. Allen O. Alves F. Andrade-Oliveira D. Brooks A. Carnero Rosell M. Carrasco Kind J. Carretero M. Costanzi L. N. da Costa T. M. Davis S. Desai J. De Vicente H. T. Diehl S. Dodelson P. Doel S. Everett B. Flaugher J. Frieman J. García-Bellido R. Gassis G. Giannini D. Grün G. Gutierrez S. R. Hinton D. L. Hollowood D. J. James K. Kuehn O. Lahav S. Lee M. Lima G. Mahler J. L. Marshall R. Miquel J. Myles R. L. C. Ogando M. E. S. Pereira A. Pieres A. A. Plazas Malagón A. Porredon C. L. Reichardt A. K. Romer S. Samuroff E. Sanchez D. Sanchez Cid I. Sevilla-Noarbe M. Schubnell M. Smith E. Suchyta M. E. C. Swanson A. Tamošiūnas G. Tarle D. L. Tucker V. Vikram N. Weaverdyck J. Weller P. Wiseman Physik Department T31 Technische Universität München James-Franck-Straße 1 D-85748 Garching Germany University Observatory Faculty of Physics Ludwig-Maximilians-Universität Scheinerstraße 1 D-81679 München Germany Excellence Cluster ORIGINS Boltzmannstraße 2 D-85748 Garching Germany Max Planck Institute for Extraterrestrial Physics Gießenbachstraße 1 D-85748 Garching Germany Kavli Institute for Cosmology Cambridge Madingley Road Cambridge CB3 0HA United Kingdom Department of Applied Mathematics and Theoretical Physics University of Cambridge Cambridge CB3 0WA United Kingdom High-Energy Physics Division Argonne National Laboratory 9700 South Cass Avenue Lemont Illinois 60439 USA Kavli Institute for Cosmological Physics University of Chicago 5640 South Ellis Avenue Chicago Illinois 60637 USA Universität Innsbruck Institut für Astro- und Teilchenphysik Technikerstraße 25/8 6020 Innsbruck Austria Argelander-Institut für Astronomie Auf dem Hügel 71 53121 Bonn Germany Laboratório Interinstitucional de e-Astronomia—LIneA Rua General José Cristino 77 Rio de Janeiro 20921-40 Brazill Fermi National Accelerator Laboratory P.O. Box 500 Batavia Illinois 60510 USA Kavli Institute for Particle Astrophysics and Cosmology Stanford University Stanford California 94305 USA SLAC National Accelerator Laboratory 2575 Sand Hill Road Menlo Park California 94025 USA Department of Physics University of Michigan Ann Arbor Michigan 48109 USA Department of Physics and Astronomy University College London Gower Street London WC1E 6BT United Kingdom Instituto de Astrofisica de Canarias E-38205 La Laguna Tenerife Spain Universidad de La Laguna Departamento de Astrofísica E-38206 La Laguna Tenerife Spain Center for Astrophysical Surveys National Center for Supercomputing Applications 1205 West Clark Street Urbana Illinois 61801 USA Institut de Física d’Altes Energies (IFAE) The Barcelona Institute of Science and Technology Campus UAB 08193 Bellaterra (Barcelona) Spain

We use galaxy cluster abundance measurements from the South Pole Telescope enhanced by multicomponent matched filter confirmation and complemented with mass information obtained using weak-lensing data from Dark Energy Survey Year 3 (DES Y3) and targeted Hubble Space Telescope observations for probing deviations from the cold dark matter paradigm. Concretely, we consider a class of dark sector models featuring interactions between dark matter (DM) and a dark radiation (DR) component within the framework of the effective theory of structure formation (ETHOS). We focus on scenarios that lead to power suppression over a wide range of scales, and thus can be tested with data sensitive to large scales, as realized, for example, for DM–DR interactions following from an unbroken non-Abelian SU(N) gauge theory (interaction rate with power-law index n=0 within the ETHOS parametrization). Cluster abundance measurements are mostly sensitive to the amount of DR interacting with DM, parametrized by the ratio of DR temperature to the cosmic microwave background (CMB) temperature, ξDR=TDR/TCMB. We find an upper limit ξDR<17% at 95% credibility. When the cluster data are combined with Planck 2018 CMB data along with baryon acoustic oscillation (BAO) measurements we find ξDR<10%, corresponding to a limit on the abundance of interacting DR that is around 3 times tighter than that from CMB + BAO data alone. We also discuss the complementarity of weak lensing informed cluster abundance studies with probes sensitive to smaller scales, explore the impact on our analysis of massive neutrinos, and comment on a slight preference for the presence of a nonzero interacting DR abundance, which enables a physical solution to the S8 tension.

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Corrigendum: Hyperuniformity variation with quasicrystal local isomorphism class

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Journal of physics. Condensed matter : an Institute of Physics journal 2017年第47期29卷 2017 Aug 8页

作者： C Lin P J Steinhardt S Torquato Department of Physics Princeton University Princeton NJ 08544 United States of America. Princeton Center for Theoretical Science Princeton University Princeton NJ 08544 United States of America. Department of Chemistry Princeton University Princeton NJ 08544 United States of America. Program of Applied and Computational Mathematics Princeton University Princeton NJ 08544 United States of America. Princeton Institute for the Science and Technology of Materials Princeton University Princeton NJ 08544 United States of America.

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On the Particle Approximation of Lagged Feynman-Kac Formulae

arXiv

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arXiv 2024年

作者： Awadelkarim, Elsiddig Caffarel, Michel Moral, Pierre Del Jasra, Ajay Applied Mathematics and Computational Science Program Computer Electrical and Mathematical Sciences and Engineering Division King Abdullah University of Science and Technology Thuwal23955-6900 Saudi Arabia University of Toulouse CNRS-Lab. de Chimie et Physique Quantiques Toulouse31062 France Centre de Recherche Inria Bordeaux Sud-Ouest Talence33405 France School of Data Science The Chinese University Hong Kong Shenzhen China

In this paper we examine the numerical approximation of the limiting invariant measure associated with Feynman-Kac formulae. These are expressed in a discrete time formulation and are associated with a Markov chain and a potential function. The typical application considered here is the computation of eigenvalues associated with non-negative operators as found, for example, in physics or particle simulation of rare-events. We focus on a novel lagged approximation of this invariant measure, based upon the introduction of a ratio of time-averaged Feynman-Kac marginals associated with a positive operator iterated l ∈ N times;a lagged Feynman-Kac formula. This estimator and its approximation using Diffusion Monte Carlo (DMC) have been extensively employed in the physics literature. In short, DMC is an iterative algorithm involving N ∈ N particles or walkers simulated in parallel, that undergo sampling and resampling operations. In this work, it is shown that for the DMC approximation of the lagged Feynman-Kac formula, one has an almost sure characterization of the L1-error as the time parameter (iteration) goes to infinity and this is at most of O(exp{−κl}/N), for_ κ > 0. In addition a non-asymptotic in time, and time uniform L1−bound is proved which is O(l/√N). We also prove a novel central limit theorem to give a characterization of the exact asymptotic in time variance. This analysis demonstrates that the strategy used in physics, namely, to run DMC with N and l small and, for long time enough, is mathematically justified. Our results also suggest how one should choose N and l in practice. We emphasize that these results are not restricted to physical applications;they have broad relevance to the general problem of particle simulation of the Feynman-Kac formula, which is utilized in a great variety of scientific and engineering fields. © 2024, CC BY.

关键词： Eigenvalues and eigenfunctions

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clotFoam: An Open-Source Framework to Simulate Blood Clot Formation Under Arterial Flow

arXiv

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arXiv 2023年

作者： Montgomery, David Municchi, Federico Leiderman, Karin Department of Applied Mathematics and Statistics Colorado School of Mines 1500 Illinois St GoldenCO80401 United States Department of Mechanical Engineering Colorado School of Mines 1500 Illinois St GoldenCO80401 United States Department of Mathematics University of North Carolina at Chapel Hill 216 Lenoir Dr Chapel HillNC27599 United States Computational Medicine Program University of North Carolina at Chapel Hill 216 Lenoir Dr Chapel HillNC27599 United States

Blood clotting involves the coupled processes of platelet aggregation and coagulation. Simulating clotting under flow in complex geometries is challenging due to multiple temporal and spatial scales and high computational cost. clotFoam is an open-source software developed in OpenFOAM that employs a continuum model of platelet advection, diffusion, and aggregation in a dynamic fluid environment and a simplified coagulation model with proteins that advect, diffuse, and react within the fluid and with wall-bound species through reactive boundary conditions. Our framework provides the foundation on which one can build more complex models and perform reliable simulations in almost any computational domain. © 2023, CC BY.

关键词： Coagulation

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An Immersed Interface Method for Incompressible Flows and Geometries with Sharp Features

arXiv

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arXiv 2024年

作者： Facci, Michael J. Kolahdouz, Ebrahim M. Griffith, Boyce E. Department of Mathematics University of North Carolina Chapel HillNC United States Flatiron Institute Simons Foundation New YorkNY United States Department of Biomedical Engineering University of North Carolina Chapel HillNC United States Carolina Center for Interdisciplinary Applied Mathematics University of North Carolina Chapel HillNC United States Computational Medicine Program University of North Carolina School of Medicine Chapel HillNC United States McAllister Heart Institute University of North Carolina School of Medicine Chapel HillNC United States

The immersed interface method (IIM) for models of fluid flow and fluid-structure interaction imposes jump conditions that capture stress discontinuities generated by forces that are concentrated along immersed boundaries. Most prior work using the IIM for fluid dynamic applications has focused on smooth interfaces, but boundaries with sharp features such as corners and edges can appear in practical analyses, particularly on engineered structures. The present study builds on our work to integrate finite element-type representations of interface geometries with the IIM. Initial realizations of this approach used a continuous Galerkin (CG) finite element discretization for the boundary, but as we show herein, these approaches generate large errors near sharp geometrical features. To overcome this difficulty, this study introduces an IIM approach using discontinuous Galerkin (DG) representation of the jump conditions. Numerical examples explore the impacts of different interface representations on accuracy for both smooth and sharp boundaries, particularly flows interacting with fixed interface configurations. We demonstrate that using a DG approach provides accuracy that is comparable to the CG method for smooth cases. Further, we identify a time step size restriction for the CG representation that is directly related to the sharpness of the geometry. In contrast, time step size restrictions imposed by DG representations are demonstrated to be insensitive to the presence of sharp *** Codes 76-10 (Primary) 76D05 (Secondary) © 2024, CC BY-NC-ND.

关键词： Incompressible flow

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Effect of non-Gaussian lensing deflections on CMB lensing measurements

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Physical Review D 2018年第12期98卷 123510-123510页

作者： Vanessa Böhm Blake D. Sherwin Jia Liu J. Colin Hill Marcel Schmittfull Toshiya Namikawa Berkeley Center for Cosmological Physics University of California Berkeley California 94720 USA Lawrence Berkeley National Laboratory 1 Cyclotron Road Berkeley California 93720 USA Department of Applied Mathematics and Theoretical Physics University of Cambridge Wilberforce Road Cambridge CB3 0WA United Kingdom Department of Astrophysical Sciences Princeton University Princeton New Jersey 08544 USA Center for Computational Astrophysics Flatiron Institute 162 5th Avenue New York New York 10010 USA Institute for Advanced Study Einstein Drive Princeton New Jersey 08540 USA Leung Center for Cosmology and Particle Astrophysics National Taiwan University Taipei 10617 Taiwan

We investigate the impact of non-Gaussian lensing deflections on measurements of the CMB lensing power spectrum. We find that the false assumption of their Gaussianity significantly biases these measurements in current and future experiments at the percent level. The bias is detected by comparing CMB lensing reconstructions from simulated CMB data lensed with Gaussian deflection fields to reconstructions from simulations lensed with fully non-Gaussian deflection fields. The non-Gaussian deflections are produced by ray tracing through snapshots of an N-body simulation and capture both the non-Gaussianity induced by nonlinear structure formation and by multiple correlated deflections. We find that the amplitude of the measured bias can be modeled with analytic expressions for a lensing bispectrum-induced bias derived by Böhm et al. in 2016 when post-Born corrections are included in the lensing bispectrum model. The bias is largest in temperature-based measurements, where it is detected with a significance of 2.84σ in the power spectrum of reconstructed convergence fields. Cross-correlating the reconstruction with the noiseless input convergence fields results in a 5.21σ detection. We do not find evidence for the bias in measurements from a combination of polarization fields (EB,EB). We argue that this non-Gaussian bias should be even more important for measurements of cross-correlations of CMB lensing with low-redshift tracers of large-scale structure.

关键词： Cosmic microwave background Evolution of the Universe Gravitational lenses Large scale structure of the Universe Sky surveys

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Multigoal-oriented error estimation and mesh adaptivity for fluid-structure interaction

arXiv

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arXiv 2021年

作者： Ahuja, K. Endtmayer, B. Steinbach, M.C. Wick, Thomas Discipline of Computer Science and Engineering Indian Institute of Technology Indore India Leibniz Universität Hannover Institut für Angewandte Mathematik Welfengarten 1 Hannover30167 Germany Leibniz Universität Hannover Germany Université Paris-Saclay ENS Paris-Saclay LMT - Laboratoire de Mécanique et Technologie Gif-sur-Yvette91190 France Johannes Kepler University Linz Doctoral Program on Computational Mathematics Altenbergerstr. 69 LinzA-4040 Austria Austrian Academy of Sciences Johann Radon Institute for Computational and Applied Mathematics Altenbergerstr. 69 LinzA-4040 Austria

In this work, we consider multigoal-oriented error estimation for stationary fluid-structure interaction. The problem is formulated within a variational-monolithic setting using arbitrary Lagrangian-Eulerian coordinates. Employing the dual-weighted residual method for goal-oriented a posteriori error estimation, adjoint sensitivities are required. For multigoal-oriented error estimation, a combined functional is formulated such that several quantities of interest are controlled simultaneously. As localization technique for mesh refinement we employ a partition-of-unity. Our algorithmic developments are substantiated with several numerical tests such as an elastic lid-driven cavity with two goal functionals, an elastic bar in a chamber with two goal functionals, and the FSI-1 benchmark with three goal *** Codes 65N30, 65N50, 74F10 © 2021, CC BY-NC-ND.

关键词： Fluid structure interaction

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Low-Frequency variability in massive stars: Core generation or surface phenomenon?

arXiv

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arXiv 2019年

作者： Lecoanet, Daniel Cantiello, Matteo Quataert, Eliot Couston, Louis-Alexandre Burns, Keaton J. Pope, Benjamin J.S. Jermyn, Adam S. Favier, Benjamin Le Bars, Michael Princeton Center for Theoretical Science Princeton University PrincetonNJ08544 United States Department of Astrophysical Sciences Princeton Univesity PrincetonNJ08544 United States Center for Computational Astrophysics Flatiron Institute New YorkNY10010 United States Astronomy Department Theoretical Astrophysics Center University of California BerkeleyCA94720 United States Cnrs Aix Marseille Université Centrale Marseille Irphe Umr 7342 Marseille13013 France British Antarctic Survey Cambridge CB3 0ET United Kingdom Department of Applied Mathematics and Theoretical Physics University of Cambridge CambridgeCB3 0WA United Kingdom Department of Mathematics Massachusetts Institute of Technology CambridgeMA02139 United States Center for Cosmology and Particle Physics Department of Physics New York University New YorkNY10003 United States Center for Data Science New York University New YorkNY10011 United States

Bowman et al. (2019a) reported low-frequency photometric variability in 164 O- and B-type stars observed with K2 and TESS. They interpret these motions as internal gravity waves, which could be excited stochastically by convection in the cores of these stars. The detection of internal gravity waves in massive stars would help distinguish between massive stars with convective or radiative cores, determine core size, and would provide important constraints on massive star structure and evolution. In this work, we study the observational signature of internal gravity waves generated by core convection. We calculate the wave transfer function, which links the internal gravity wave amplitude at the base of the radiative zone to the surface luminosity variation. This transfer function varies by many orders of magnitude for frequencies 1, and has regularly-spaced peaks near 1d"1due to standing modes. This is inconsistent with the observed spectra which have smooth "red noise" profiles, without the predicted regularly-spaced peaks. The wave transfer function is only meaningful if the waves stay predominatly linear. We next show that this is the case: low frequency traveling waves do not break unless their luminosity exceeds the radiative luminosity of the star;and, the observed luminosity fluctuations at high frequencies are so small that standing modes would be stable to nonlinear instability. These simple calculations suggest that the observed low-frequency photometric variability in massive stars is not due to internal gravity waves generated in the core of these stars. We finish with a discussion of (sub)surface convection, which produces low-frequency variability in low-mass stars, very similar to that observed in Bowman et al. (2019a) in higher mass stars. Copyright © 2019, The Authors. All rights reserved.

关键词： Luminance

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