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31st International Symposium on Lattice Field Theory, LATTICE 2013

作者： Alexandrou, Constantia Negele, John W. Petschlies, Marcus Department of Physics University of Cyprus P.O. Box 20537 Nicosia1678 Cyprus Computation-based Science and Technology Research Center Cyprus Institute 20 Kavafi Str. Nicosia2121 Cyprus Laboratory for Nuclear Science and Department of Physics Center for Theoretical Physics Massachusetts Institute of Technology CambridgeMA02139 United States

A method suitable for extracting resonance parameters of unstable baryons in lattice QCD is examined. The method is applied to the strong decay of the Δ to a pion-nucleon state, extracting the pND coupling constant a... 详细信息

关键词： Hadrons

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Coherence dynamics of a two-mode Bose-Einstein condensate coupled with the environment

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Physical Review A 2013年第6期88卷 063642-063642页

作者： Yixiao Huang Qing-Shou Tan Li-Bin Fu Xiaoguang Wang Zhejiang Institute of Modern Physics Department of Physics Zhejiang University Hangzhou 310027 China National Key Laboratory of Science and Technology on Computation Physics Institute of Applied Physics and Computational Mathematics Beijing 100088 China

We investigate the coherence dynamics of a two-mode Bose-Einstein condensate coupled with the environment in the mean-field approximation. We give an analytical result of the time-average coherence in the absence of system-environment coupling, and find that the time-average coherence attains its maximum value at the critical point which corresponds to the boundary between the self-trapping regime and the Josephson oscillation regime. The effect of noise on dynamical coherence is also considered by analyzing the couplings of the condensate to the environment. With the first kind of coupling, the coherence finally stabilizes at a fixed value. Meanwhile, we show that the presence of the noise can even enhance the coherence for some particular interaction. With the second kind of coupling as collisional dephasing, the noise leads a sudden transition of the coherence which then subjects to an exponential decay.

关键词： COHERENT states DYNAMICS BOSE-Einstein condensation MEAN field theory APPROXIMATION theory CRITICAL point

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Quantum phase transition in a three-level atom-molecule system

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Physical Review A 2013年第1期88卷 013602-013602页

作者： Sheng-Chang Li Li-Bin Fu Fu-Li Li School of Science Xi'an Jiaotong University Xi'an 710049 China National Key Laboratory of Science and Technology on Computation Physics Institute of Applied Physics and Computational Mathematics Beijing 100088 China Center for Applied Physics and Technology Peking University Beijing 100084 China

We adopt a three-level bosonic model to investigate the quantum phase transition in an ultracold atom-molecule conversion system which includes one atomic mode and two molecular modes. Through thoroughly exploring the properties of energy-level structure, fidelity, and adiabatic geometric phase, we confirm that the system exhibits a second-order phase transition from an atom-molecule mixture phase to a pure molecule phase. We give the explicit expression of the critical point and obtain two scaling laws to characterize this transition. In particular, we find that both the critical exponents and the behavior of the ground-state geometric phase have obviously changed in contrast to a similar two-level model. Our analytical calculations show that the ground-state geometric phase jumps from zero to π/3 at the critical point. This discontinuous behavior has been checked by numerical simulations and it can be used to identify the phase transition in the system.

关键词： QUANTUM phase transitions ATOM-molecule collisions GEOMETRIC quantum phases COMPUTER simulation PHASE transformations (physics) CRITICAL point

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Determination of Δ-resonance parameters from lattice QCD

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Physical Review D 2013年第3期88卷 031501(R)-031501(R)页

作者： C. Alexandrou J. W. Negele M. Petschlies A. Strelchenko A. Tsapalis Department of Physics University of Cyprus P.O. Box 20537 1678 Nicosia Cyprus Computation-based Science and Technology Research Center Cyprus Institute 20 Kavafi Street 2121 Nicosia Cyprus Laboratory for Nuclear Science and Department of Physics Center for Theoretical Physics Massachusetts Institute of Technology Cambridge Massachusetts 02139 USA Scientific Computing Division Fermilab P.O. Box 500 Batavia Illinois 60510-5011 USA Hellenic Naval Academy Hatzikyriakou Avenue Pireaus 18539 Greece and Department of Physics National Technical University of Athens Zografou Campus 15780 Athens Greece

关键词： QCD sum rules (Nuclear physics) RESONANCE COUPLING constants (Nuclear physics) BARYONS PARAMETER estimation

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Formation of N-body polymer molecules through generalized stimulated Raman adiabatic passage

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Physical Review A 2013年第4期87卷 043631-043631页

作者： Fu-quan Dou Li-bin Fu Jie Liu College of Physics and Electronic Engineering Northwest Normal University Lanzhou 730070 China School of Physics Beijing Institute of Technology Beijing 100081 China National Laboratory of Science and Technology on Computation Physics Institute of Applied Physics and Computational Mathematics Beijing 100088 China Key Laboratory of High Energy Density Physics Simulation Center for Applied Physics and Technology Peking University Beijing 100084 China

We investigate the creation of stable homonuclear and heteronuclear N-body polymer molecules from ultracold atoms via a generalized stimulated Raman adiabatic passage scheme. The atom-molecule dark-state solutions for the system are obtained and are found to satisfy universal algebraic equations. We discuss the linear instability and the adiabatic fidelity of the dark state. We also explore the effects of the interparticle interactions, the atomic number of the polymer, and external field parameters on the conversion process.

关键词： DARK states (Quantum optics) ADIABATIC processes MANY-body problem ATOMS ALGEBRAIC equations ATOMIC number

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Subcycle Dynamics of Coulomb Asymmetry in Strong Elliptical Laser Fields

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Physical Review Letters 2013年第2期111卷 023006-023006页

作者： Min Li Yunquan Liu Hong Liu Qicheng Ning Libin Fu Jie Liu Yongkai Deng Chengyin Wu Liang-You Peng Qihuang Gong Department of Physics and State Key Laboratory for Mesoscopic Physics Peking University Beijing 100871 People’s Republic of China National Key Laboratory of Science and Technology on Computation Physics Institute of Applied Physics and Computational Mathematics Beijing 100088 People’s Republic of China Center for Applied Physics and Technology Peking University Beijing 100084 People’s Republic of China

We measure photoelectron angular distributions of noble gases in intense elliptically polarized laser fields, which indicate strong structure-dependent Coulomb asymmetry. Using a dedicated semiclassical model, we have disentangled the contribution of direct ionization and multiple forward scattering on Coulomb asymmetry in elliptical laser fields. Our theory quantifies the roles of the ionic potential and initial transverse momentum on Coulomb asymmetry, proving that the small lobes of asymmetry are induced by direct ionization and the strong asymmetry is induced by multiple forward scattering in the ionic potential. Both processes are distorted by the Coulomb force acting on the electrons after tunneling. Lowering the ionization potential, the relative contribution of direct ionization on Coulomb asymmetry substantially decreases and Coulomb focusing on multiple rescattering is more important. We do not observe evident initial longitudinal momentum spread at the tunnel exit according to our simulation.

关键词： COULOMB'S law IONIZATION energy IONIZATION (Atomic physics) ELECTRON tunneling MOMENTUM distributions

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Improving helpful actions for contingent planning with enforced observations

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Journal of computational Information Systems 2013年第7期9卷 2691-2698页

作者： Wei, Wei Ouyang, Dantong Zhao, Xiangfu Zhang, Liming College of Computer Science and Technology Jilin University Changchun 130012 China Key Laboratory of Symbolic Computation and Knowledge Engineering of Ministry of Education Changchun 130012 China College of Mathematics Physics and Information Engineering Zhejiang Normal University Jinhua 321004 China

We tackle the problem of improving the helpful actions technique for contingent planning. A revision of the heuristic computation that rearranges the relaxed planning graph is proposed, where the unreasonable conformant actions can be excluded from the resulting helpful actions collection and replaced with enforced observation to the belief state. Pruning with the improved helpful actions, we consequently cut all the non-branching plans out of the solution space. Experimental results show that our method brings considerable improvements in both of plan quality and runtime efficiency. Copyright © 2013 Binary Information Press.

关键词： Information systems

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Mean-field embedding of the dual-fermion approach for correlated electron systems

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Physical Review E 2013年第6期88卷 063306-063306页

作者： S.-X. Yang H. Terletska Z. Y. Meng J. Moreno M. Jarrell Department of Physics and Astronomy Louisiana State University Baton Rouge Louisiana 70803 USA Center for Computation and Technology Louisiana State University Baton Rouge Louisiana 70803 USA Condensed Matter Physics and Materials Science Department Brookhaven National Laboratory Upton New York 11973 USA

To reduce the rapidly growing computational cost of the dual-fermion lattice calculation with increasing system size, we introduce two embedding schemes. One is the real fermion embedding, and the other is the dual-fermion embedding. Our numerical tests show that the real fermion and dual-fermion embedding approaches converge to essentially the same result. The application on the Anderson disorder and Hubbard models shows that these embedding algorithms converge more quickly with system size as compared to the conventional dual-fermion method, for the calculation of both single- and two-particle quantities.

关键词： FERMIONS RESEARCH HUBBARD model ENERGY-band theory of solids ANDERSON model ELECTRIC conductivity CONDUCTION band LATTICE theory STATISTICAL physics

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Pragmatic optimizations for better scientific utilization of large supercomputers

Pragmatic optimizations for better scientific utilization of...

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作者： Dubey, Anshu Calder, Alan C. Daley, Christopher Fisher, Robert T. Graziani, C. Jordan, George C. Lamb, Donald Q. Reid, Lynn B. Townsley, Dean M. Weide, Klaus Flash Center for Computational Science Astronomy and Astrophysics Computation Institute University of Chicago 5747 South Ellis Avenue Chicago IL 60637 United States Argonne National Laboratory Argonne IL United States Department of Physics and Astronomy Stony Brook University United States Department of Physics University of Massachusetts Dartmouth United States NTEC Environmental Technology Subiaco WA Australia University of Western Australia Crawley WA Australia Department of Physics and Astronomy University of Alabama United States

Advances in modeling and algorithms, combined with growth in computing resources, have enabled simulations of multiphysics-multiscale phenomena that can greatly enhance our scientific understanding. However, on currently available high-performance computing (HPC) resources, maximizing the scientific outcome of simulations requires many trade-offs. In this paper we describe our experiences in running simulations of the explosion phase of Type Ia supernovae on the largest available platforms. The simulations use FLASH, a modular, adaptive mesh, parallel simulation code with a wide user base. The simulations use multiple physics components: hydrodynamics, gravity, a sub-grid flame model, a three-stage burning model, and a degenerate equation of state. They also use Lagrangian tracer particles, which are then post-processed to determine the nucleosynthetic yields. We describe the simulation planning process, and the algorithmic optimizations and trade-offs that were found to be necessary. Several of the optimizations and trade-offs were made during the course of the simulations as our understanding of the challenges evolved, or when simulations went into previously unexplored physical regimes. We also briefly outline the anticipated challenges of, and our preparations for, the next-generation computing platforms. © 2012 The Author(s).

关键词： Supercomputers

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Dual fermion method for disordered electronic systems

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Physical Review B 2013年第13期87卷 134208-134208页

作者： H. Terletska S.-X. Yang Z. Y. Meng J. Moreno M. Jarrell Condensed Matter Physics and Materials Science Department Brookhaven National Laboratory Upton New York 11973 USA Department of Physics and Astronomy Louisiana State University Baton Rouge Louisiana 70803 USA Center for Computation and Technology Louisiana State University Baton Rouge Louisiana 70803 USA

While the coherent potential approximation (CPA) is the prevalent method for the study of disordered electronic systems, it fails to capture nonlocal correlations and Anderson localization. To incorporate such effects, we extend the dual fermion approach to disordered systems using the replica method. The developed method utilizes the exact mapping to the dual fermion variables, and includes intersite scattering via diagrammatic perturbation theory in the dual variables. The CPA is recovered as a zeroth-order approximation. Results for single- and two-particle quantities show good agreement with a cluster extension of the CPA; moreover, weak localization is captured. As a natural extension of the CPA, our method presents an alternative to existing nonlocal cluster theories for disordered systems, and has potential applications in the study of disordered systems with electronic interactions.

关键词： ELECTRONIC systems ANDERSON localization FERMIONS PARTICLES (Nuclear physics) CONDENSED matter

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