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Numerical meshless solution of high-dimensional sine-gordon equations via fourier HDMR-HC approximation

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arXiv 2019年

作者： Xu, Xin Luo, Xiaopeng Rabitz, Herschel Department of Chemistry Princeton University PrincetonNJ08544 United States School of Managment and Engineering Nanjing University Nanjing210008 China Program in Applied and Computational Mathematics Princeton University PrincetonNJ08544 United States

In this paper, an implicit time stepping meshless scheme is proposed to find the numerical solution of high-dimensional sine-Gordon equations (SGEs) by combining the high dimensional model representation (HDMR) and the Fourier hyperbolic cross (HC) approximation. To ensure the sparseness of the relevant coefficient matrices of the implicit time stepping scheme, the whole domain is first divided into a set of subdomains, and the relevant derivatives in high-dimension can be separately approximated by the Fourier HDMR-HC approximation in each subdomain. The proposed method allows for stable large time-steps and a relatively small number of nodes with satisfactory accuracy. The numerical examples show that the proposed method is very attractive for simulating the high-dimensional SGEs. Copyright © 2019, The Authors. All rights reserved.

关键词： Numerical methods

Second-order semi-implicit projection methods for micromagnetics simulations

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arXiv 2019年

作者： Xie, Changjian García-Cervera, Carlos J. Wang, Cheng Zhou, Zhennan Chen, Jingrun School of Mathematical Sciences Soochow University Suzhou215006 China Department of Mathematics University of California Santa BarbaraCA93106 United States Basque Center for Applied Mathematics Mazarredo 14 Bilbao Basque CountryE48009 Spain Mathematics Department University of Massachusetts Dartmouth North DartmouthMA02747 United States Beijing International Center for Mathematical Research Peking University Beijing China Mathematical Center for Interdisciplinary Research Soochow University Suzhou215006 China

Micromagnetics simulations require accurate approximation of the magnetization dynamics described by the Landau-Lifshitz-Gilbert equation, which is nonlinear, nonlocal, and has a non-convex constraint, posing interesting challenges in developing numerical methods. In this paper, we propose two second-order semi-implicit projection methods based on the second-order backward differentiation formula and the second-order interpolation formula using the information at previous two temporal steps. Unconditional unique solvability of both methods is proved, with their second-order accuracy verified through numerical examples in both 1D and 3D. The efficiency of both methods is compared to that of another two popular methods. In addition, we test the robustness of both methods for the first benchmark problem with a ferromagnetic thin film material from National Institute of Standards and *** Codes 35K55, 35Q70, 65N06, 65N12 Copyright © 2019, The Authors. All rights reserved.

关键词： Ferromagnetic materials

Featurized bidirectional GAN: Adversarial defense via adversarially learned semantic inference

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arXiv 2018年

作者： Bao, Ruying Liang, Sihang Wang, Qingcan Program in Applied and Computational Mathematics Princeton University Department of Physics Princeton University

Deep neural networks have been demonstrated to be vulnerable to adversarial attacks, where small perturbations intentionally added to the original inputs can fool the classifier. In this paper, we propose a defense method, Featurized Bidirectional Generative Adversarial Networks (FBGAN), to extract the semantic features of the input and filter the non-semantic perturbation. FBGAN is pre-trained on the clean dataset in an unsupervised manner, adversarially learning a bidirectional mapping between the high-dimensional data space and the low-dimensional semantic space;also mutual information is applied to disentangle the semantically meaningful features. After the bidirectional mapping, the adversarial data can be reconstructed to denoised data, which could be fed into any pre-trained classifier. We empirically show the quality of reconstruction images and the effectiveness of defense. Copyright © 2018, The Authors. All rights reserved.

关键词： Generative adversarial networks

Meshless Hermite-HDMR finite difference method for high-dimensional Dirichlet problems

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arXiv 2019年

作者： Luo, Xiaopeng Xu, Xin Rabitz, Herschel Department of Chemistry Princeton University PrincetonNJ08544 United States School of Managment and Engineering Nanjing University Nanjing210008 China Program in Applied and Computational Mathematics Princeton University PrincetonNJ08544 United States

In this paper, a meshless Hermite-HDMR finite difference method is proposed to solve high-dimensional Dirichlet problems. The approach is based on the local Hermite-HDMR expansion with an additional smoothing technique. First, we introduce the HDMR decomposition combined with the multiple Hermite series to construct a class of Hermite-HDMR approximations, and the relevant error estimate is theoretically built in a class of Hermite spaces. It can not only provide high order convergence but also retain good scaling with increasing dimensions. Then the Hermite-HDMR based finite difference method is particularly proposed for solving high-dimensional Dirichlet problems. By applying a smoothing process to the Hermite-HDMR approximations, numerical stability can be guaranteed even with a small number of nodes. Numerical experiments in dimensions up to 30 show that resulting approximations are of very high quality. Copyright © 2019, The Authors. All rights reserved.

关键词： Finite difference method

Measurement of cosmic-ray muon spallation products in a xenon-loaded liquid scintillator with KamLAND

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Physical Review C 2023年第5期107卷 054612-054612页

作者： S. Abe S. Asami M. Eizuka S. Futagi A. Gando Y. Gando T. Gima A. Goto T. Hachiya K. Hata K. Hosokawa K. Ichimura S. Ieki H. Ikeda K. Inoue K. Ishidoshiro Y. Kamei N. Kawada Y. Kishimoto M. Koga M. Kurasawa T. Mitsui H. Miyake T. Nakahata K. Nakamura R. Nakamura H. Ozaki T. Sakai I. Shimizu J. Shirai K. Shiraishi A. Suzuki Y. Suzuki A. Takeuchi K. Tamae H. Watanabe Y. Yoshida S. Obara A. K. Ichikawa S. Yoshida S. Umehara K. Fushimi K. Kotera Y. Urano B. E. Berger B. K. Fujikawa J. G. Learned J. Maricic S. N. Axani Z. Fu J. Smolsky L. A. Winslow Y. Efremenko H. J. Karwowski D. M. Markoff W. Tornow S. Dell'Oro T. O'Donnell J. A. Detwiler S. Enomoto M. P. Decowski K. M. Weerman C. Grant A. Li H. Song Research Center for Neutrino Science Tohoku University Sendai 980-8578 Japan Department of Human Science Obihiro University of Agriculture Veterinary Medicine Obihiro Hokkaido 080-8555 Japan Institute for the Physics and Mathematics of the Universe The University of Tokyo Kashiwa 277-8568 Japan Graduate Program on Physics for the Universe Tohoku University Sendai 980-8578 Japan Frontier Research Institute for Interdisciplinary Sciences Tohoku University Sendai 980-8578 Japan Department of Physics Tohoku University Sendai 980-8578 Japan Graduate School of Science Osaka University Toyonaka Osaka 560-0043 Japan Research Center for Nuclear Physics (RCNP) Osaka University Ibaraki Osaka 567-0047 Japan Graduate School of Advanced Technology and Science Tokushima University Tokushima 770-8506 Japan Graduate School of Integrated Arts and Sciences Tokushima University Tokushima 770-8502 Japan Nuclear Science Division Lawrence Berkeley National Laboratory Berkeley California 94720 USA Department of Physics and Astronomy University of Hawaii at Manoa Honolulu Hawaii 96822 USA Massachusetts Institute of Technology Cambridge Massachusetts 02139 USA Department of Physics and Astronomy University of Tennessee Knoxville Tennessee 37996 USA Triangle Universities Nuclear Laboratory Durham North Carolina 27708 USA The University of North Carolina at Chapel Hill Chapel Hill North Carolina 27599 USA North Carolina Central University Durham North Carolina 27701 USA Physics Department at Duke University Durham North Carolina 27705 USA Center for Neutrino Physics Virginia Polytechnic Institute and State University Blacksburg Virginia 24061 USA Center for Experimental Nuclear Physics and Astrophysics University of Washington Seattle Washington 98195 USA Nikhef and the University of Amsterdam Science Park Amsterdam the Netherlands Boston University Boston Massachusetts 02215 USA

Cosmic-ray muons produce various radioisotopes when passing through material. These spallation products can be backgrounds for rare event searches such as in solar neutrino, double-β decay, and dark matter search experiments. The KamLAND-Zen experiment searches for neutrinoless double-β decay in 745 kg of xenon dissolved in liquid scintillator. The experiment includes dead-time-free electronics with a high efficiency for detecting muon-induced neutrons. The production yields of different radioisotopes are measured with a combination of delayed coincidence techniques, newly developed muon reconstruction, and xenon spallation identification methods. The observed xenon spallation products are consistent with results from the fluka and geant4 simulation codes.

关键词： Nuclear reactions Nuclear structure & decays Cosmic ray & astroparticle detectors

An algorithm based on Voronoi diagrams for the multi-stream multi-source multicast routing problem

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International Journal of Innovative Computing and Applications 2018年第4期9卷 216-229页

作者： De Andrade, Romerito Campos Goldbarg, Marco César Goldbarg, Elizabeth Ferreira Gouveâ Postgraduate Program in Systems and Computation Federal University of Rio Grande Do Norte Campus Universitário Lagoa Nova Natal RN Brazil Department of Informatics and Applied Mathematics Federal University of Rio Grande Do Norte Campus Universitário Lagoa Nova Natal RN Brazil

In this study, we present a new heuristic for the multi-stream multi-source multicast routing problem. The core of the heuristic proposed in this study is based on a generalisation of Voronoi diagrams in graphs. It allows building the trees needed to serve the demands of multiple sessions efficiently. Also, the proposed algorithm supports multiple sources. We performed an extensive experimental analysis of different network and problem configurations such as the number of sessions, nodes, sources and participants per session. We compare the proposed algorithm to heuristics proposed previously. The results of the experiments showed that the heuristic proposed in this study finds high-quality solutions efficiently. © 2018 Inderscience Enterprises Ltd.

关键词： Multicasting

The 230 GHz Variability of Numerical Models of Sagittarius A* I. Parameter Surveys on Varying Ion-electron Temperature Ratios Under Strongly Magnetized Conditions

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arXiv 2023年

作者： Chan, Ho-Sang Chan, Chi-Kwan Prather, Ben S. Wong, George N. Gammie, Charles Department of Physics Institute of Theoretical Physics The Chinese University of Hong Kong N.T. Shatin Hong Kong JILA University of Colorado National Institute of Standards and Technology 440 UCB BoulderCO80309-0440 United States Department of Astrophysical and Planetary Sciences University of Colorado 391 UCB BoulderCO80309 United States Steward Observatory Department of Astronomy University of Arizona 933 N. Cherry Avenue TucsonAZ85721 United States Data Science Institute University of Arizona 1230 N. Cherry Avenue TucsonAZ85721 United States Program in Applied Mathematics University of Arizona 617 North Santa Rita TucsonAZ85721 United States Los Alamos National Lab Los AlamosNM87545 United States School of Natural Sciences Institute for Advanced Study 1 Einstein Drive PrincetonNJ08540 United States Princeton Gravity Initiative Princeton University PrincetonNJ08544 United States Department of Physics University of Illinois at Urbana-Champaign 1110 West Green Street UrbanaIL61801 United States Department of Astronomy University of Illinois at Urbana-Champaign 1002 West Green Street UrbanaIL61801 United States NCSA University of Illinois at Urbana-Champaign 1205 W. Clark St. UrbanaIL61801 United States Illinois Center for the Advanced Study of the Universe University of Illinois at Urbana-Champaign 1110 West Green St. UrbanaIL61801 United States

The 230 GHz lightcurves of Sagittarius A* (Sgr A*) predicted by general relativistic magnetohydrodynamics (GRMHD) and ray-tracing (GRRT) models in Event Horizon Telescope Collaboration et al. (2022) have higher variability M∆T compared to observations. In this series of papers, we explore the origin of such large brightness variability. In this first paper, we performed large GRRT parameter surveys that span from the optically thin to the optically thick regimes, covering the ion-electron temperature ratio under strongly magnetized conditions, RLow, from 1 to 60. We find that increasing RLow can lead to either an increase or a reduction in M∆T depending on other model parameters, making it consistent with the observed variability of Sgr A* in some cases. Our analysis of GRRT image snapshots finds that the major contribution to the large M∆T for the RLow = 1 models comes from the photon rings. However, secondary contributions from the accretion flow are also visible depending on the spin parameter. Our work demonstrates the importance of the electron temperature used for modelling radiatively inefficient accretion flows and places new constraints on the ion-electron temperature ratio. A more in-depth analysis for understanding the dependencies of M∆T on RLow will be performed in subsequent papers. © 2023, CC BY.

关键词： Black holes

Tuning phototactic robots with sensorial delays

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Physical Review E 2018年第5期98卷 052606-052606页

作者： Maximilian Leyman Freddie Ogemark Jan Wehr Giovanni Volpe Department of Physics University of Gothenburg SE-41296 Gothenburg Sweden Department of Physics Chalmers University of Technology SE-41296 Gothenburg Sweden Department of Mathematics and Program in Applied Mathematics University of Arizona Tucson Arizona 85721 USA

The presence of a delay between sensing and reacting to a signal can determine the long-term behavior of autonomous agents whose motion is intrinsically noisy. In a previous work [Mijalkov, McDaniel, Wehr, and Volpe, Phys. Rev. X 6, 011008 (2016)], we have shown that sensorial delay can alter the drift and the position probability distribution of an autonomous agent whose speed depends on the illumination intensity it measures. In this work, we consider an agent whose speed and rotational diffusion both depend on the illumination intensity and are subject to two independent sensorial delays. Using theory, simulations, and experiments with a phototactic robot, we study the dependence of the drift and of the probability distribution of the robot's position on the sensorial delays. In particular, the radial drift may have a positive as well as negative sign, and the position probability density peaks in different regions, depending on the choice of the model's parameters. This not only generalizes previous work but also explores new phenomena resulting from the interaction between the two delay variables.

关键词： Active matter

First measurement of the strange axial coupling constant using neutral-current quasielastic interactions of atmospheric neutrinos at KamLAND

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Physical Review D 2023年第7期107卷 072006-072006页

作者： S. Abe S. Asami M. Eizuka S. Futagi A. Gando Y. Gando T. Gima A. Goto T. Hachiya K. Hata K. Ichimura S. Ieki H. Ikeda K. Inoue K. Ishidoshiro Y. Kamei N. Kawada Y. Kishimoto M. Koga M. Kurasawa T. Mitsui H. Miyake T. Nakahata K. Nakamura R. Nakamura H. Ozaki T. Sakai I. Shimizu J. Shirai K. Shiraishi A. Suzuki Y. Suzuki A. Takeuchi K. Tamae H. Watanabe Y. Yoshida S. Obara A. K. Ichikawa S. Yoshida S. Umehara K. Fushimi K. Kotera Y. Urano B. E. Berger B. K. Fujikawa J. G. Learned J. Maricic S. N. Axani Z. Fu J. Smolsky L. A. Winslow Y. Efremenko H. J. Karwowski D. M. Markoff W. Tornow J. A. Detwiler S. Enomoto M. P. Decowski C. Grant A. Li H. Song S. Dell’Oro T. O’Donnell Research Center for Neutrino Science Tohoku University Sendai 980-8578 Japan Department of Human Science Obihiro University of Agriculture and Veterinary Medicine Obihiro 080-8555 Japan Kavli Institute for the Physics and Mathematics of the Universe (WPI) The University of Tokyo Institutes for Advanced Study The University of Tokyo Kashiwa Chiba 277-8583 Japan Graduate Program on Physics for the Universe Tohoku University Sendai 980-8578 Japan Frontier Research Institute for Interdisciplinary Sciences Tohoku University Sendai 980-8578 Japan Department of Physics Tohoku University Sendai 980-8578 Japan Graduate School of Science Osaka University Toyonaka Osaka 560-0043 Japan Research Center for Nuclear Physics Osaka University Ibaraki Osaka 567-0047 Japan Department of Physics Tokushima University Tokushima 770-8506 Japan Graduate School of Integrated Arts and Sciences Tokushima University Tokushima 770-8502 Japan Nuclear Science Division Lawrence Berkeley National Laboratory Berkeley California 94720 USA Department of Physics and Astronomy University of Hawaii at Manoa Honolulu Hawaii 96822 USA University of Delaware Newark Delaware 19716 USA Massachusetts Institute of Technology Cambridge Massachusetts 02139 USA Department of Physics and Astronomy University of Tennessee Knoxville Tennessee 37996 USA Triangle Universities Nuclear Laboratory Durham North Carolina 27708 USA Physics Departments at Duke University Durham North Carolina 27708 USA North Carolina Central University Durham North Carolina 27707 USA and The University of North Carolina at Chapel Hill Chapel Hill North Carolina 27599 USA Center for Experimental Nuclear Physics and Astrophysics University of Washington Seattle Washington 98195 USA Nikhef and the University of Amsterdam Science Park Amsterdam The Netherlands Boston University Boston Massachusetts 02215 USA Center for Neutrino Physics Virginia Polytechnic Institute and State University Blacksburg Virginia 24061 US

We report a measurement of the strange axial coupling constant gAs using atmospheric neutrino data at KamLAND. This constant is a component of the axial form factor of the neutral-current quasielastic (NCQE) interaction. The value of gAs significantly changes the ratio of proton and neutron NCQE cross sections. KamLAND is suitable for measuring NCQE interactions as it can detect nucleon recoils with low-energy thresholds and measure neutron multiplicity with high efficiency. KamLAND data, including the information on neutron multiplicity associated with the NCQE interactions, makes it possible to measure gAs with a suppressed dependence on the axial mass MA, which has not yet been determined. For a comprehensive prediction of the neutron emission associated with neutrino interactions, we establish a simulation of particle emission via nuclear deexcitation of C12, a process not considered in existing neutrino Monte Carlo event generators. Energy spectrum fitting for each neutron multiplicity gives gAs=−0.14−0.26+0.25, which is the most stringent limit obtained using NCQE interactions without MA constraints. The two-body current contribution considered in this analysis relies on a theoretically effective model and electron scattering experiments and requires future verification by direct measurements and future model improvement.

关键词： Neutrinos