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Stability of quantum motion in regular systems: A uniform semiclassical approach

Physical Review E 2007年第1期75卷 016201-016201页

作者： Wen-ge Wang G. Casati Baowen Li Department of Physics and Centre for Computational Science and Engineering National University of Singapore 117542 Republic of Singapore Department of Physics Southeast University Nanjing 210096 China Center for Nonlinear and Complex Systems Università degli Studi dell’Insubria Via Valleggio 11 22100 Como Italy CNR-INFM and Istituto Nazionale di Fisica Nucleare Sezione di Milano Italy Laboratory of Modern Acoustics and Institute of Acoustics Nanjing University 210093 China NUS Graduate School for Integrative Sciences and Engineering National University of Singapore 117597 Republic of Singapore

We study the stability of quantum motion of classically regular systems in the presence of small perturbations. On the basis of a uniform semiclassical theory we derive the fidelity decay which displays a quite complex behavior, from Gaussian to power law decay t−α, with 1⩽α⩽2. Semiclassical estimates are given for the time scales separating the different decaying regions, and numerical results are presented which confirm our theoretical predictions.

关键词： CHAOTIC systems FIDELITY DYNAMICS DECAY

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Interaction-induced quantum ratchet in a Bose-Einstein condensate

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Physical Review A 2007年第2期76卷 023421-023421页

作者： Dario Poletti Giuliano Benenti Giulio Casati Baowen Li Department of Physics and Centre for Computational Science and Engineering National University of Singapore Singapore 117542 Republic of Singapore CNISM CNR-INFM and Center for Nonlinear and Complex Systems Università degli Studi dell’Insubria Via Valleggio 11 22100 Como Italy Istituto Nazionale di Fisica Nucleare Sezione di Milano via Celoria 16 20133 Milano. Italy Laboratory of Modern Acoustics and Institute of Acoustics Nanjing University 210093 People’s Republic of China NUS Graduate School for Integrative Sciences and Engineering 117597 Republic of Singapore

We study the dynamics of a dilute Bose-Einstein condensate confined in a toroidal trap and exposed to a pair of periodically flashed optical lattices. We first prove that in the noninteracting case this system can present a quantum symmetry which forbids the ratchet effect classically expected. We then show how many-body atom-atom interactions, treated within the mean-field approximation, can break this quantum symmetry, thus generating directed transport.

关键词： BROWNIAN MOTORS BILLIARDS SYMMETRY DYNAMICS

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Ratchet Effect and the Transporting Islands in the Chaotic Sea

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Physical Review Letters 2007年第24期99卷 244101-244101页

作者： Lei Wang Giuliano Benenti Giulio Casati Baowen Li Department of Physics and Centre for Computational Science and Engineering National University of Singapore Singapore 117542 Republic of Singapore Department of Physics Renmin University of China Beijing 100872 People’s Republic of China CNISM CNR-INFM and Center for Nonlinear and Complex Systems Università degli Studi dell’Insubria Via Valleggio 11 22100 Como Italy Istituto Nazionale di Fisica Nucleare Sezione di Milano Via Celoria 16 20133 Milano Italy NUS Graduate School of Integrative Sciences and Engineering Singapore 117597 Republic of Singapore

We study directed transport in a classical deterministic dissipative system. We consider the generic case of mixed phase space and show that large ratchet currents can be generated thanks to the presence, in the Hamiltonian limit, of transporting stability islands embedded in the chaotic sea. Because of the simultaneous presence of chaos and dissipation the stationary value of the current is independent of initial conditions, except for initial states with very small measure.

关键词： Electron transitions

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Skyrmion-like states in two- and three-dimensional dynamical lattices

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Physical Review E 2007年第2期75卷 026603-026603页

作者： P. G. Kevrekidis R. Carretero-González D. J. Frantzeskakis B. A. Malomed F. K. Diakonos Department of Mathematics and Statistics University of Massachusetts Amherst Massachusetts 01003-4515 USA Nonlinear Dynamical Systems Group * Department of Mathematics and Statistics and Computational Science Research Center† San Diego State University San Diego California 92182-7720 USA Department of Physics University of Athens Panepistimiopolis Zografos Athens 15784 Greece Department of Interdisciplinary Studies Faculty of Engineering Tel Aviv University Tel Aviv 69978 Israel

We construct, in discrete two-component systems with cubic nonlinearity, stable states emulating Skyrmions of the classical field theory. In the two-dimensional case, an analog of the baby Skyrmion is built on the square lattice as a discrete vortex soliton of a complex field [whose vorticity plays the role of the Skyrmion’s winding number (WN)], coupled to a radial “bubble” in a real lattice field. The most compact quasi-Skyrmion on the cubic lattice is composed of a nearly planar complex-field discrete vortex and a three-dimensional real-field bubble; unlike its continuum counterpart which must have WN=2, this stable discrete state exists with WN=1. Analogs of Skyrmions in the one-dimensional lattice are also constructed. Stability regions for all these states are found in an analytical approximation and verified numerically. The dynamics of unstable discrete Skyrmions (which leads to the onset of lattice turbulence) and their partial stabilization by external potentials are explored too.

关键词： WAVE-GUIDE ARRAYS NONLINEAR SCHRODINGER LATTICES SPATIAL OPTICAL SOLITONS DISCRETE SOLITONS PHOTONIC LATTICES BREATHERS STABILITY VORTEX LIGHT GAP

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Polarized states and domain walls in spinor Bose-Einstein condensates

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Physical Review A 2007年第6期76卷 063603-063603页

作者： H. E. Nistazakis D. J. Frantzeskakis P. G. Kevrekidis B. A. Malomed R. Carretero-González A. R. Bishop Department of Physics University of Athens Panepistimiopolis Zografos Athens 15784 Greece Department of Mathematics and Statistics University of Massachusetts Amherst Massachusetts 01003-4515 USA Department of Interdisciplinary Studies Faculty of Engineering Tel Aviv University Tel Aviv 69978 Israel Nonlinear Dynamical Systems Group Department of Mathematics and Statistics and Computational Science Research Center San Diego State University San Diego California 92182-7720 USA Theoretical Division and Center for Nonlinear Studies Los Alamos National Laboratory Los Alamos New Mexico 87545 USA

We study spin-polarized states and their stability in the antiferromagnetic phase of spinor (F=1) quasi-one-dimensional Bose-Einstein condensates. Using analytical approximations and numerical methods, we find various types of polarized states, including patterns of the Thomas-Fermi type, structures featuring a pulse in one component inducing a hole in the other components, states with holes in all three components, and domain walls (DWs). The stability analysis based on the Bogoliubov–de Gennes equations reveals intervals of weak oscillatory instability in families of these states, except for the DWs, which are always stable. The development of the instabilities is examined by means of direct simulations.

关键词： .weak Instability Oscillatory condensates states with holes direct simulations walls in spinor

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Thermal energy reservoirs from processed lunar regolith

Thermal energy reservoirs from processed lunar regolith

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5th International Energy Conversion engineering Conference

作者： Wegeng, Robert S. Mankins, John C. Taylor, Lawrence A. Sanders, G.B. Batteile Memorial Institute Pacific Northwest National Laboratory United States Artemisinnovation Management Solutions Earth and Planetary Sciences Department University of Tennessee United States National Aeronautics and Space Administration Johnson Space Center United States Process Science and Engineering Department Pacific Northwest National Laboratory P.O. Box 999 Richland WA 99352 United States ArtemisInnovation Management Solutions 43446 Thistlewood Court Ashburn VA 20147 United States Planetary Geosciences Institute Department of Earth and Planetary Sciences University of Tennessee Knoxville TN 37996 United States Energy Systems Division NASA Johnson Space Center Mail Code EP 2101 NASA Road 1 Houston TX 77058 United States

ISBN: (纸本)1563479028

NASA's plan for returning to the Moon includes the early establishment of a human outpost, where energy and power will be at a premium, particularly during the lunar night. To permit occupation during the full lunar 27-day diurnal cycle, energy storage will be required. The use of engineered, Thermal Energy Reservoirs (TERs) is one of several energy-storage options. While actual lunar regolith is a poor thermal-mass material, it can readily be processed to yield improved thermophysical properties. Establishing the ability to produce thermal-mass materials from lunar regolith reduces the cost of bringing energystorage materials from Earth and provides a source of heat and supplemental electrical power during periods of darkness. This paper discusses methods of producing thermal-mass materials from lunar regolith, engineering concepts for lunar TERs, and system configurations that could provide heat and electricity. This paper also includes the results of preliminary calculations, bounding the potentials and limitations of lunar TERs.

关键词： Reservoirs (water)

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Čerenkov-like radiation in a binary superfluid flow past an obstacle

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Physical Review A 2007年第5期75卷 055601-055601页

作者： H. Susanto P. G. Kevrekidis R. Carretero-González B. A. Malomed D. J. Frantzeskakis A. R. Bishop Department of Mathematics and Statistics University of Massachusetts Amherst Massachusetts 01003-4515 USA Nonlinear Dynamical Systems Group Department of Mathematics and Statistics and Computational Science Research Center San Diego State University San Diego California 92182-7720 USA Department of Interdisciplinary Studies Faculty of Engineering Tel Aviv University Tel Aviv 69978 Israel Department of Physics University of Athens Panepistimiopolis Zografos Athens 15784 Greece Theoretical Division and Center for Nonlinear Studies Los Alamos National Laboratory Los Alamos New Mexico 87545 USA

We consider the dynamics of two coupled miscible Bose-Einstein condensates, when an obstacle is dragged through them. The existence of two different speeds of sound provides the possibility for three dynamical regimes: when both components are subcritical, we do not observe nucleation of coherent structures; when both components are supercritical they both form dark solitons in one dimension (1D) and vortices or rotating vortex dipoles in two dimensions; in the intermediate regime, we observe the nucleation of a structure in the form of a dark-antidark soliton in 1D; the 2D analog of such a structure, a vortex-lump, is also observed.

关键词： Vortex flow

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Towards data-driven modeling and simulation of multiphysics degrading systems 16

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16th European Conference of Fracture

作者： Michopoulos, J.G. Farhat, C. Computational Multiphysics Systems Lab Center for Computational Material Science Special Projects Group WashingtonDC20375 United States Department of Mechanical Engineering Institute for Computational and Mathematical Engineering Stanford University StanfordCA94305 United States

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On data-driven modeling and simulation of aero-thermo-mechanically degrading nonlinear continuum systems

On data-driven modeling and simulation of aero-thermo-mechan...

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2006 ASME International Design engineering Technical Conferences and Computers and Information In engineering Conference, DETC2006

作者： Michopoulos, J.G. Farhat, C. Bou-Mosleh, C. Computational Multiphysics Systems Lab. Special Projects Group Center for Computational Material Science Washington DC 20375 United States Department of Mechanical Engineering Institute for Computational and Mathematical Engineering Stanford University Stanford CA 94305 United States

ISBN: (纸本)079183784X

Recent advances on data-driven application systems, sensor and computational technologies as well as long-term needs for efficient and accurate systemic behavior prediction monitoring in the context of realistic system design and maintenance, have brought degrading continuum systems modeling and simulation in the forefront of our activities. This paper outlines the initial steps of a methodology for applying a data-driven inverse-problem approach on the area of modeling mass-conserving degrading thermo-mechanical multi-domain nonlinear continuum structural and material systems. The methodology is applied for composite materials under simultaneous mechanical and thermal multi-field excitation and is based on mechatronic and computational automation. Furthermore, the multi-domain multiphysics modeling necessary for addressing the fluid-structure interaction involved in such systems is also discussed in the context of jet platforms with aerodynamically induced heating. Finally, simulation demonstrations are presented for the F-16 fighter jet and for a sensor-driven data solution reconstruction of an aircraft wing to demonstrate the potential for developing a material and structural health monitoring system based on he concept of dissipated energy density as a material health metric. Copyright © 2006 by ASME.

关键词： Continuum mechanics

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Mining frequent itemsets from noisy data 22

Mining frequent itemsets from noisy data

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22nd International Conference on Data engineering Workshops, ICDEW 2006

作者： Narita, Kasuyo Kitagawa, Hiroyuki Master's Programs in Science and Engineering University of Tsukuba Tennodai Tsukuba Japan Graduate School of Systems and Information Engineering Center for Computational Sciences University of Tsukuba Tennodai Tsukuba Japan

ISBN: (纸本)0769525717

As we face huge amounts of varied information, data mining, which helps us discover hidden features or rules from voluminous data systematically, has become more important [3, 4, 6, 10]. However, real world data is often dirty, including noise such as missing or irrelevant values. The information mined from such noisy data may be incorrect. We model noisy data with probabilities, assuming that noise is mixed with data statistically. We also propose a way to find frequent itemsets [2] by estimating supports on noiseless data from noisy data. An algorithm using FP-Tree [6, 10] is also presented to mine frequent itemsets efficiently. © 2006 IEEE.

关键词： Data mining

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