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Testing an exact diffraction formula with gravitational wave source lensed by a supermassive black hole in binary systems

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arXiv 2024年

作者： Guo, Xiao Cao, Zhoujian School of Fundamental Physics and Mathematical Sciences Hangzhou Institute for Advanced Study University of Chinese Academy of Sciences Hangzhou310024 China Institute of Applied Mathematics Academy of Mathematics and Systems Science Chinese Academy of Sciences Beijing100190 China

When it comes to long-wavelength gravitational waves (GWs), diffraction effect becomes significant when these waves are lensed by celestial bodies. Typically, the traditional diffraction integral formula neglects large-angle diffraction, which is often adequate for most of cases. Nonetheless, there are specific scenarios, such as when a GW source is lensed by a supermassive black hole in a binary system, where the lens and source are in close proximity, where large-angle diffraction can play a crucial role. In our prior research, we have introduced an exact, general diffraction integral formula that accounts for large-angle diffraction as well. This paper explores the disparities between this exact diffraction formula and the traditional, approximate one under various special conditions. Our findings indicate that, under specific parameters — such as a lens-source distance of DLS = 0.1 AU and a lens mass of ML = 4 × 106Mo — the amplification factor for the exact diffraction formula is notably smaller than that of the approximate formula, differing by a factor of approximately rF 0.806. This difference is substantial enough to be detectable. Furthermore, our study reveals that the proportionality factor rF gradually increases from 0.5 to 1 as DLS increases, and decreases as ML increases. Significant differences between the exact and approximate formulas are observable when DLS 0.2 AU (assuming ML = 4 × 106Mo) or when ML 2 × 106Mo (assuming DLS = 0.1 AU). These findings suggest that there is potential to validate our general diffraction formula through future GW detections. Copyright © 2024, The Authors. All rights reserved.

关键词： Gravity waves

Differential and integral cross sections for the valence-shell excitations in D2O studied by fast electron impact

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Physical Review A 2022年第6期105卷 062817-062817页

作者： Zi-Ru Ma Shu-Xing Wang Yi-Geng Peng Jian-Hui Zhu Yuan-Chen Xu Xiao-Jiao Du Li-Han Wang Wei-Qing Xu Yong Wu Jian-Guo Wang Lin-Fan Zhu Department of Modern Physics University of Science and Technology of China Hefei Anhui 230026 China Department of Applied Physics Nanjing University of Science and Technology Nanjing 210094 China Institute of Applied Physics and Computational Mathematics Beijing 100088 China Center for Transformative Science ShanghaiTech University Shanghai 201210 China HEDPS Center for Applied Physics and Technology and College of Engineering Peking University Beijing 100871 China

The experimental generalized oscillator strengths (GOSs) for the valence-shell excitations of heavy water in 6.50–12.17 eV are determined by fast electron scattering with an incident electron energy of 1500 eV and an energy resolution of 80 meV. The experimental data of the Ã1B1←X̃1A1 transition between H2O and D2O show significant discrepancies around the minimum, and further theoretical calculations with nuclear effects accounted are recommended. The comparisons of the present GOSs of Ã1B1←X̃1A1 and B̃1A1←X̃1A1 transitions in D2O with theoretical calculations within the first Born approximation and the second Born approximation indicate that the higher Born terms become prominent at large momentum transfers. In particular, the GOSs of the dipole-forbidden transition 1A2←X̃1A1 are extracted, benefiting from the present high-energy electron scattering, where most of electronic dipole-forbidden transitions are not involved. By extrapolating the GOSs to the zero momentum transfer, the optical oscillator strengths for the corresponding dipole-allowed transitions are determined, which provide an independent cross-check for previous optical measurements. Moreover, the integral Born cross sections are scaled to an accurate level with the aid of the binding energy–excitation energy–scaling method. The relevant experimental data in this work can supplement the molecular database with electron collision data involving heavy water.

关键词： Atomic & molecular collisions Electronic excitation & ionization Electronic transitions

Spatial second-order positive and asymptotic preserving filtered PN schemes for nonlinear radiative transfer equations

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arXiv 2023年

作者： Xu, Xiaojing Jiang, Song Sun, Wenjun School of Mathematics and Information Science Guangxi University Guangxi Nanning530004 China School of Mathematics and Physics Southwest University of Science and Technology Sichuan Mianyang621010 China Institute of Applied Physics and Computational Mathematics Fenghao East Road 2 Beijing100094 China Center for Applied Physics and Technology College of Engineering Peking University Beijing100871 China

A spatial second-order scheme for the nonlinear radiative transfer equations is introduced in this paper. The discretization scheme is based on the filtered spherical harmonics (FPN) method for the angular variable and the unified gas kinetic scheme (UGKS) framework for the spatial and temporal variables respectively. In order to keep the scheme positive and second-order accuracy, firstly, we use the implicit Monte Carlo (IMC) linearization method [6] in the construction of the UGKS numerical boundary fluxes. This is an essential point in the construction. Then, by carefully analyzing the constructed second-order fluxes involved in the macro-micro decomposition, which is induced by the FPN angular discretization, we establish the sufficient conditions that guarantee the positivity of the radiative energy density and material temperature. Finally, we employ linear scaling limiters for the angular variable in the PN reconstruction and for the spatial variable in the piecewise linear slopes reconstruction respectively, which are shown to be realizable and reasonable to enforce the sufficient conditions holding. Thus, the desired scheme, called the PPFPN-based UGKS, is obtained. Furthermore, we can show that in the regime ϵ 1 and the regime ϵ = O(1), the second-order fluxes can be simplified. And, a simplified spatial second-order scheme, called the PPFPN-based SUGKS, is thus presented, which possesses all the properties of the non-simplified one. Inheriting the merit of UGKS, the proposed schemes are asymptotic preserving. By employing the FPN method for the angular variable, the proposed schemes are almost free of ray effects. Moreover, the above-mentioned way of imposing the positivity would not destroy both AP and second-order accuracy properties. To our best knowledge, this is the first time that spatial second-order, positive, asymptotic preserving and almost free of ray effects schemes are constructed for the nonlinear radiative transfer equations without operato

关键词： Radiative transfer

Fabrication of hydrophobic surfaces of aluminum alloys by laser irradiation

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Fabrication of hydrophobic surfaces of aluminum alloys by la...

2022 International Conference Laser Optics, ICLO 2022

作者： Abramov, Andrey Samyshkin, Vlad Osipov, Anton Kutrovskaya, Stella Stoletov Vladimir State University Department of Physics and Applied Mathematics Gorkii street Vladimir600000 Russia School of Science Westlake University Hangzhou310024 China Institute of Natural Sciences Westlake Institute for Advanced Study Hangzhou310024 China

ISBN: (数字)9781665466646

ISBN: (纸本)9781665466646

Laser modification of aluminum alloys with inclusions of B4C microparticles is of significant interest due to a significant increase in strength and temperature characteristics of the obtained material. In the process of laser irradiation of a composite material with an aluminum matrix, it is possible to form cluster objects that change the density of alloying additives distribution on the surface. In this work, we propose the creation of hydrophobic surfaces with macrogeometry controlled by the laser beam trajectory, and microgeometry determined by the target surface modification processes during local laser heating © 2022 IEEE.

关键词： Contact angle

Balanced training for sparse GANs 23

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Balanced training for sparse GANs

Proceedings of the 37th International Conference on Neural Information Processing Systems

作者： Yite Wang Jing Wu Naira Hovakimyan Ruoyu Sun University of Illinois Urbana-Champaign School of Data Science The Chinese University of Hong Kong Shenzhen China and Shenzhen International Center for Industrial and Applied Mathematics Shenzhen Research Institute of Big Data

Over the past few years, there has been growing interest in developing larger and deeper neural networks, including deep generative models like generative adversarial networks (GANs). However, GANs typically come with high computational complexity, leading researchers to explore methods for reducing the training and inference costs. One such approach gaining popularity in supervised learning is dynamic sparse training (DST), which maintains good performance while enjoying excellent training efficiency. Despite its potential benefits, applying DST to GANs presents challenges due to the adversarial nature of the training process. In this paper, we propose a novel metric called the balance ratio (BR) to study the balance between the sparse generator and discriminator. We also introduce a new method called balanced dynamic sparse training (ADAPT), which seeks to control the BR during GAN training to achieve a good trade-off between performance and computational cost. Our proposed method shows promising results on multiple datasets, demonstrating its effectiveness. Our code is available at https://***/YiteWang/ADAPT.

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Evaluating Optimal Reference Translations

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arXiv 2023年

作者： Zouhar, Vilém Kloudová, Věra Popel, Martin Bojar, Ondřej ETH Zürich Department of Computer Science Switzerland Institute of Formal and Applied Linguistics Faculty of Mathematics and Physics Charles University Czech Republic

The overall translation quality reached by current machine translation (MT) systems for high-resourced language pairs is remarkably good. Standard methods of evaluation are not suitable nor intended to uncover the many translation errors and quality deficiencies that still persist. Furthermore, the quality of standard reference translations is commonly questioned and comparable quality levels have been reached by MT alone in several language pairs. Navigating further research in these high-resource settings is thus difficult. In this article, we propose a methodology for creating more reliable document-level human reference translations, called "optimal reference translations," with the simple aim to raise the bar of what should be deemed "human translation quality." We evaluate the obtained document-level optimal reference translations in comparison with "standard" ones, confirming a significant quality increase and also documenting the relationship between evaluation and translation editing. © 2023, CC BY.

关键词： Quality control

Theoretical prediction of superconductivity in two-dimensional hydrogenated metal diboride: M2B2H(M=Al, Mg, Mo, W)

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Physical Review Materials 2023年第11期7卷 114802-114802页

作者： Yu-Lin Han Hao-Dong Liu Na Jiao Meng-Meng Zheng Hong-Yan Lu Bao-Tian Wang Ping Zhang School of Physics and Physical Engineering Qufu Normal University Qufu 273165 China Institute of High Energy Physics Chinese Academy of Sciences Beijing 100049 China Spallation Neutron Source Science Center Dongguan 523803 China Institute of Applied Physics and Computational Mathematics Beijing 100088 China

In recent years, superconductivity in two-dimensional (2D) layered metal borides has aroused much interest. Here, based on first-principles calculations, we theoretically report four 2D hydrogenated metal diborides: M2B2H(M=Al, Mg, Mo, W), and investigate their geometrical structures, electronic structures, phonon dispersions, thermal stability, dynamic stability, electron-phonon coupling (EPC), superconducting properties, and so on. Results reveal that the introduction of hydrogen atoms expands the frequency range of the phonon spectrum of monolayer M2B2, and significantly increases the EPC. We systematically analyze the specific origins of superconductivity in these hydrogenated low-dimensional systems. The obtained EPC constants λ of M2B2H(M=Al, Mg, Mo, W) are 2.93, 0.86, 1.09, and 1.40, and the corresponding superconducting transition temperatures (Tc) are 52.6, 23.2, 21.5, and 18.6 K, respectively. By further applying electron/hole doping or biaxial tensile strain, the Tc can be further increased, with the highest Tc of 60.2 K in Al2B2H under 0.4% biaxial tensile strain. The predicted M2B2H provides a new platform for 2D superconductivity and may have potential applications in 2D nanodevices.

关键词： Electronic structure Phonons Superconductivity 2-dimensional systems High-temperature superconductors Superconductors BCS theory First-principles calculations

Deep potentials for materials science

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Materials Futures 2022年第2期1卷 89-115页

作者： Tongqi Wen Linfeng Zhang Han Wang Weinan E David J Srolovitz Department of Mechanical Engineering The University of Hong KongHong KongHong Kong Special Administrative Region of China DP Technology BeijingPeople’s Republic of China AI for Science Institute BeijingPeople’s Republic of China Laboratory of Computational Physics Institute of Applied Physics and Computational MathematicsBeijingPeople’s Republic of China HEDPS CAPTCollege of EngineeringPeking UniversityBeijingPeople’s Republic of China School of Mathematical Sciences Peking UniversityBeijingPeople’s Republic of China Department of Mathematics and Program in Applied and Computational Mathematics Princeton UniversityPrincetonNJUnited States of America International Digital Economy Academy(IDEA) ShenzhenPeople’s Republic of China

To fill the gap between accurate(and expensive)ab initio calculations and efficient atomistic simulations based on empirical interatomic potentials,a new class of descriptions of atomic interactions has emerged and been widely applied;*** learning potentials(MLPs).One recently developed type of MLP is the deep potential(DP)*** this review,we provide an introduction to DP methods in computational materials *** theory underlying the DP method is presented along with a step-by-step introduction to their development and *** also review materials applications of DPs in a wide range of materials *** DP Library provides a platform for the development of DPs and a database of extant *** discuss the accuracy and efficiency of DPs compared with ab initio methods and empirical potentials.

关键词： deep potential atomistic simulation machine learning potential neural network

Numerical simulation of singularity propagation modeled by linear convection equations with spatially heterogeneous nonlocal interactions

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arXiv 2022年

作者： Yu, Xiaoxuan Xu, Yan Du, Qiang School of Mathematical Sciences University of Science and Technology of China Anhui Hefei230026 China Department of Applied Physics and Applied Mathematics Data Science Institute Columbia University New YorkNY10027 United States

We study the propagation of singularities in solutions of linear convection equations with spatially heterogeneous nonlocal interactions. A spatially varying nonlocal horizon parameter is adopted in the model, which measures the range of nonlocal interactions. Via heterogeneous localization, this can lead to the seamless coupling of the local and nonlocal models. We are interested in understanding the impact on singularity propagation due to the heterogeneities of nonlocal horizon and the local and nonlocal transition. We first analytically derive equations to characterize the propagation of different types of singularities for various forms of nonlocal horizon parameters in the nonlocal regime. We then use asymptotically compatible schemes to discretize the equations and carry out numerical simulations to illustrate the propagation patterns in different scenarios. Copyright © 2022, The Authors. All rights reserved.

关键词： Numerical models