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Global optical model potential describing 12C-nucleus elastic scattering

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Chinese physics C 2020年第12期44卷 123-132页

作者： Yong-Li Xu Yin-Lu Han Xin-Wu Su Xiao-Jun Sun Hai-Ying Liang Hai-Rui Guo Chong-Hai Cai College of Physics and Electronic Science Shanxi Datong UniversityDatong 037009China Key Laboratory of Nuclear Data China Institute of Atomic EnergyP.O.BOX(275-41)Beijing 102413China College of Physics Guangxi Normal UniversityGuilin 541004China Institute of Applied Physics and Computational Mathematics Beijing 100094China Department of Physics Nankai UniversityTianjin 300071China

We construct a new global optical model potential to describe the elastic scattering of *** experimental data of elastic-scattering angular distributions and total reaction cross sections for targets from 24Mg to 209Bi are considered below 200 MeV within the framework of the optical *** results calculated using the derived global optical potential are then compared with the existing experimental *** reliability of the global optical potential is further tested by predicting the elastic scattering data out of the mass and energy ranges,within which the global potential parameters are determined,and reasonable results are also obtained.

关键词： optical model potential elastic-scattering angular distribution reaction cross section

Observation of giant quadrupole plasmon resonance in C60 in fast ion collisions

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Physical Review A 2022年第1期106卷 012820-012820页

作者： S. Kasthurirangan C.-Z. Gao P. M. Dinh L. Gulyás E. Suraud L. C. Tribedi Department of Nuclear and Atomic Physics Tata Institute of Fundamental Research Colaba Mumbai 400005 India Department of Physics Institute of Chemical Technology Matunga Mumbai 400019 India Institute of Applied Physics and Computational Mathematics Beijing 100088 China Laboratoire de Physique Théorique Université de Toulouse CNRS UPS F-31062 Toulouse Cedex France Institute of Nuclear Research of the Hungarian Academy of Sciences (ATOMKI) H-4001 Debrecen Hungary School of Mathematics and Physics Queen's University Belfast University Road Belfast BT7 1NN Northern Ireland

Strong perturbation caused due to the Coulomb interaction with fast highly charged ions has been used to probe the quadrupole plasmon excitation in C60 fullerene. The electron-emission spectrum arising from a free C60 molecule reveals a double-peak structure due to the decay of the giant plasmon resonance. Using a state-of-the-art theoretical approach describing the electron dynamics by time-dependent density functional theory, with an explicit ionic background these two peaks are unambiguously identified as arising from the dipole and quadrupole modes of the plasmon. Furthermore, the electron angular distribution clearly shows a double-well-type distribution which is well reproduced by quadrupole and plasmon resonances. The dipole and quadrupole excitations combined with a long-range postcollisional Coulomb interaction shows excellent agreement with the observed anisotropic angular distribution. The present paper serves as an independent confirmation of the presence of a substantial quadrupole plasmon contribution in molecular systems.

关键词： Atomic & molecular clusters Electronic excitation & ionization

A Universal Description of Stochastic Oscillators

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arXiv 2023年

作者： Pérez-Cervera, Alberto Gutkin, Boris Thomas, Peter J. Lindner, Benjamin Universidad Complutense de Madrid Instituto de Matemática Inderdisciplinar Madrid Spain Group for Neural Theory LNC2 INSERM U960 DEC Ecole Normale Supérieure - PSL University Paris France Department of Mathematics Applied Mathematics and Statistics Case Western Reserve University ClevelandOH United States Department of Physics Bernstein Center for Computational Neuroscience Humboldt University Berlin Germany

Many systems in physics, chemistry and biology exhibit oscillations with a pronounced random component. Such stochastic oscillations can emerge via different mechanisms, for example linear dynamics of a stable focus with fluctuations, limit-cycle systems perturbed by noise, or excitable systems in which random inputs lead to a train of pulses. Despite their diverse origins, the phenomenology of random oscillations can be strikingly similar. Here we introduce a nonlinear transformation of stochastic oscillators to a new complex-valued function Q∗1(x) that greatly simplifies and unifies the mathematical description of the oscillator’s spontaneous activity, its response to an external time-dependent perturbation, and the correlation statistics of different oscillators that are weakly coupled. The function Q∗1(x) is the eigenfunction of the Kolmogorov backward operator with the least negative (but non-vanishing) eigenvalue λ1 = µ1 + iω1. The resulting power spectrum of the complex-valued function is exactly given by a Lorentz spectrum with peak frequency ω1 and half-width µ1;its susceptibility with respect to a weak external forcing is given by a simple one-pole filter, centered around ω1;and the cross-spectrum between two coupled oscillators can be easily expressed by a combination of the spontaneous power spectra of the uncoupled systems and their susceptibilities. Our approach makes qualitatively different stochastic oscillators comparable, provides simple characteristics for the coherence of the random oscillation, and gives a framework for the description of weakly coupled oscillators. Copyright © 2023, The Authors. All rights reserved.

关键词： Power spectrum

Emulating Complex Synapses Using Interlinked Proton Conductors

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arXiv 2024年

作者： Zhang, Lifu Li, Ji-An Hu, Yang Jiang, Jie Lai, Rongjie Benna, Marcus K. Shi, Jian Department of Materials Science and Engineering Rensselaer Polytechnic Institute TroyNY12180 United States Neurosciences Graduate Program University of California San Diego La Jolla CA92093 United States Department of Mathematics Purdue University West LafayetteIN47907 United States Department of Neurobiology School of Biological Sciences University of California at San Diego La Jolla CA92093 United States Department of Physics Applied Physics and Astronomy Rensselaer Polytechnic Institute TroyNY12180 United States

In terms of energy efficiency and computational speed, neuromorphic electronics based on non-volatile memory devices is expected to be one of most promising hardware candidates for future artificial intelligence (AI). However, catastrophic forgetting, networks rapidly overwriting previously learned weights when learning new tasks, remains as a pivotal hurdle in either digital or analog AI chips for unleashing the true power of brain-like computing. To address catastrophic forgetting in the context of online memory storage, a complex synapse model (the Benna-Fusi model) has been proposed recently[1], whose synaptic weight and internal variables evolve following a diffusion dynamics. In this work, by designing a proton transistor with a series of charge-diffusion-controlled storage components, we have experimentally realized the Benna-Fusi artificial complex synapse. The memory consolidation from coupled storage components is revealed by both numerical simulations and experimental observations. Different memory timescales for the complex synapse are engineered by the diffusion length of charge carriers, the capacity and number of coupled storage components. The advantage of the demonstrated complex synapse in both memory capacity and memory consolidation is revealed by neural network simulations of face familiarity detection. Our experimental realization of the complex synapse suggests a promising approach to enhance memory capacity and to enable continual learning. Copyright © 2024, The Authors. All rights reserved.

关键词： computational efficiency

THE COMPLEX INTERPLAY BETWEEN RISK TOLERANCE AND THE SPREAD OF INFECTIOUS DISEASES

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arXiv 2024年

作者： Nguyen, Maximilian Freedman, Ari Cheung, Matthew Saad-Roy, Chadi Espinoza, Baltazar Grenfell, Bryan Levin, Simon Lewis-Sigler Institute Princeton University PrincetonNJ08544 United States Department of Ecology and Evolutionary Biology Princeton University PrincetonNJ United States Program in Applied and Computational Mathematics Princeton University PrincetonNJ United States Miller Institute for Basic Research in Science Department of Integrative Biology University of California Berkeley BerkeleyCA United States Biocomplexity Institute University of Virginia CharlottesvilleVA United States

Risk-driven behavior provides a feedback mechanism through which individuals both shape and are collectively affected by an epidemic. We introduce a general and flexible compartmental model to study the effect of heterogeneity in the population with regards to risk tolerance. The interplay between behavior and epidemiology leads to a rich set of possible epidemic dynamics. Depending on the behavioral composition of the population, we find that increasing heterogeneity in risk tolerance can either increase or decrease the epidemic size. We find that multiple waves of infection can arise due to the interplay between transmission and behavior, even without the replenishment of susceptibles. We find that increasing protective mechanisms such as the effectiveness of interventions, the number of risk-averse people in the population, and the duration of intervention usage reduces the epidemic overshoot. When the protection is pushed past a critical threshold, the epidemic dynamics enter an underdamped regime where the epidemic size exactly equals the herd immunity threshold. Lastly, we can find regimes where epidemic size does not monotonically decrease with a population that becomes increasingly risk-averse. Copyright © 2024, The Authors. All rights reserved.

关键词： Epidemiology

Predicting nonequilibrium Green’s function dynamics and photoemission spectra via nonlinear integral operator learning

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arXiv 2024年

作者： Zhu, Yuanran Yin, Jia Reeves, Cian C. Yang, Chao Vlček, Vojtěch Applied Mathematics and Computational Research Division Lawerence Berkeley National Laboratory Berkeley94720 United States School of Mathematical Sciences Fudan University Shanghai200437 China Department of Physics University of California Santa Barbara Santa Barbara93117 United States Department of Chemistry and Biochemistry University of California Santa Barbara Santa Barbara93117 United States Department of Materials University of California Santa Barbara Santa Barbara93117 United States

Understanding the dynamics of nonequilibrium quantum many-body systems is an important research topic in a wide range of fields across condensed matter physics, quantum optics, and high-energy physics. However, numerical studies of large-scale nonequilibrium phenomena in realistic materials face serious challenges due to intrinsic high-dimensionality of quantum many-body problems and the absence of time-invariance. The nonequilibrium properties of many-body systems can be described by the dynamics of the correlator, or the Green’s function of the system, whose time evolution is given by a high-dimensional system of integro-differential equations, known as the Kadanoff-Baym equations (KBEs). The time-convolution term in KBEs, which needs to be recalculated at each time step, makes it difficult to perform long-time numerical simulation. In this paper, we develop an operator-learning framework based on Recurrent Neural Networks (RNNs) to address this challenge. We utilize RNNs to learn the nonlinear mapping between Green’s functions and convolution integrals in KBEs. By using the learned operators as a surrogate model in the KBE solver, we obtain a general machine-learning scheme for predicting the dynamics of nonequilibrium Green’s functions. Besides significant savings per each time step, the new methodology reduces the temporal computational complexity from O(Nt3) to O(Nt) where Nt is the number of steps taken in a simulation, thereby making it possible to study large many-body problems which are currently infeasible with conventional KBE solvers. Through various numerical examples, we demonstrate the effectiveness of the operator-learning based approach in providing accurate predictions of physical observables such as the reduced density matrix and time-resolved photoemission spectra. Moreover, our framework exhibits clear numerical convergence and can be easily parallelized, thereby facilitating many possible further developments and applications. Copyright © 2024

关键词： Quantum optics

Quantum initial conditions for curved inflating universes

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Physical Review D 2024年第12期109卷 123502-123502页

作者： M. I. Letey Z. Shumaylov F. J. Agocs W. J. Handley M. P. Hobson A. N. Lasenby Kavli Institute for Cosmology Madingley Road Cambridge CB3 0HA United Kingdom John A. Paulson School of Engineering and Applied Sciences Harvard University Cambridge Massachusetts 02138 USA Department of Applied Mathematics and Theoretical Physics University of Cambridge Wilberforce Road Cambridge CB3 0WA United Kingdom Center for Computational Mathematics Flatiron Institute 162 Fifth Avenue New York New York USA Astrophysics Group Cavendish Laboratory J. J. Thomson Avenue Cambridge CB3 0HE United Kingdom

We discuss the challenges of motivating, constructing, and quantizing a canonically normalized inflationary perturbation in spatially curved universes. We show that this has historically proved challenging due to the interaction of nonadiabaticity with spatial curvature. We construct a novel curvature perturbation that is canonically normalized in the sense of its equation of motion and is unique up to a single scalar parameter. With this construction it becomes possible to set initial conditions invariant under canonical transformations, overcoming known ambiguities in the literature. This corrected quantization has potentially observational consequences via modifications to the primordial power spectrum at large angular scales, as well as theoretical implications for quantization procedures in curved cosmologies filled with a scalar field.

关键词： Cosmic microwave background Cosmology Inflation Quantum cosmology Quantum fields in curved spacetime

Free-space realization of tunable pin-like optical vortex beams

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Photonics Research 2021年第7期9卷 1204-1212页

作者： DOMENICO BONGIOVANNI DENGHUI LI MIHALIS GOUTSOULAS HAO WU YI HU DAOHONG SONG ROBERTO MORANDOTTI NIKOLAOS KEFREMIDIS ZHIGANG CHEN MOE Key Laboratory of Weak-Light Nonlinear Photonics TEDA Applied Physics Institute and School of PhysicsNankai UniversityTianjin 300457China INRS-EMT 1650 Blvd.Lionel-BouletVarennesQuebec J3X 1S2Canada Department of Applied Mathematics University of CreteHeraklionCrete 71409Greece Institute of Fundamental and Frontier Sciences University of Electronic Science and Technology of ChinaChengdu 610054China Institute of Applied and Computational Mathematics FORTHHeraklionCrete 70013Greece Department of Physics&Astronomy San Francisco State UniversitySan FranciscoCalifornia 94132USA

We demonstrate,both analytically and experimentally,free-space pin-like optical vortex beams (POVBs). Such angular-momentum-carrying beams feature tunable peak intensity and undergo robust antidiffracting propagation,realized by judiciously modulating both the amplitude and the phase profile of a standard laser ***,they are generated by superimposing a radially symmetric power-law phase on a helical phase structure,which allows the inclusion of an orbital angular momentum term to the POVBs. During propagation in free space,these POVBs initially exhibit autofocusing dynamics,and subsequently their amplitude patterns morph into a high-order Bessel-like profile characterized by a hollow core and an annular main lobe with a constant or tunable width during propagation. In contrast with numerous previous endeavors on Bessel beams,our work represents the first demonstration of long-distance free-space generation of optical vortex "pins" with their peak intensity evolution controlled by the impressed amplitude structure. Both the Poynting vectors and the optical radiation forces associated with these beams are also numerically analyzed,revealing novel properties that may be useful for a wide range of applications.

关键词： tunable optical Bessel

Shock-induced migration of asymmetry tilt grain boundary in iron bicrystal: A case study of Σ3

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Chinese physics B 2019年第12期28卷 273-279页

作者： Xueyang Zhang Kun Wang Jun Chen Wangyu Hu Wenjun Zhu Shifang Xiao Huiqiu Deng Mengqiu Cai Department of Applied Physics School of Physics and ElectronicsHunan UniversityChangsha 410082China Laboratory of Computational Physics Institute of Applied Physics and Computational MathematicsBeijing 100088China Center for Applied Physics and Technology Peking UniversityBeijing 100087China College of Materials Science and Engineering Hunan UniversityChangsha 410082China National Key Laboratory of Shock Wave and Detonation Physics Institute of Fluid PhysicsMianyang 621900China

Many of our previous studies have discussed the shock response of symmetrical grain boundaries in iron *** this paper, the molecular dynamics simulation of an iron bicrystal containing Σ3 [110] asymmetry tilt grain boundary(ATGB) under shock-loading is performed. We find that the shock response of asymmetric grain boundaries is quite different from that of symmetric grain boundaries. Especially, our simulation proves that shock can induce migration of asymmetric grain boundary in iron. We also find that the shape and local structure of grain boundary(GB) would not be changed during shock-induced migration of Σ3 [110] ATGB, while the phase transformation near the GB could affect migration of GB. The most important discovery is that the shock-induced shear stress difference between two sides of GB is the key factor leading to GB migration. Our simulation involves a variety of piston velocities, and the migration of GB seems to be less sensitive to the piston velocity. Finally, the kinetics of GB migration at lattice level is discussed. Our work firstly reports the simulation of shock-induced grain boundary migration in iron. It is of great significance to the theory of GB migration and material engineering.

关键词： shock-loading grain boundary migration iron phase transition