1,088 research outputs found

    Entanglement Entropy and Mutual Information in Bose-Einstein Condensates

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    In this paper we study the entanglement properties of free {\em non-relativistic} Bose gases. At zero temperature, we calculate the bipartite block entanglement entropy of the system, and find it diverges logarithmically with the particle number in the subsystem. For finite temperatures, we study the mutual information between the two blocks. We first analytically study an infinite-range hopping model, then numerically study a set of long-range hopping models in one-deimension that exhibit Bose-Einstein condensation. In both cases we find that a Bose-Einstein condensate, if present, makes a divergent contribution to the mutual information which is proportional to the logarithm of the number of particles in the condensate in the subsystem. The prefactor of the logarithmic divergent term is model dependent.Comment: 12 pages, 6 figure

    Description of thermal entanglement with the static path plus random-phase approximation

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    We discuss the application of the static path plus random phase approximation (SPA+RPA) and the ensuing mean field+RPA treatment to the evaluation of entanglement in composite quantum systems at finite temperature. These methods involve just local diagonalizations and the determination of the generalized collective vibrational frequencies. As illustration, we evaluate the pairwise entanglement in a fully connected XXZ chain of nn spins at finite temperature in a transverse magnetic field bb. It is shown that already the mean field+RPA provides an accurate analytic description of the concurrence below the mean field critical region (b<bc|b|<b_c), exact for large nn, whereas the full SPA+RPA is able to improve results for finite systems in the critical region. It is proved as well that for T>0T>0 weak entanglement also arises when the ground state is separable (b>bc|b|>b_c), with the limit temperature for pairwise entanglement exhibiting quite distinct regimes for bbc|b|b_c.Comment: 20 pages, 5 figure

    Shell Model Monte Carlo method in the pnpn-formalism and applications to the Zr and Mo isotopes

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    We report on the development of a new shell-model Monte Carlo algorithm which uses the proton-neutron formalism. Shell model Monte Carlo methods, within the isospin formulation, have been successfully used in large-scale shell-model calculations. Motivation for this work is to extend the feasibility of these methods to shell-model studies involving non-identical proton and neutron valence spaces. We show the viability of the new approach with some test results. Finally, we use a realistic nucleon-nucleon interaction in the model space described by (1p_1/2,0g_9/2) proton and (1d_5/2,2s_1/2,1d_3/2,0g_7/2,0h_11/2) neutron orbitals above the Sr-88 core to calculate ground-state energies, binding energies, B(E2) strengths, and to study pairing properties of the even-even 90-104 Zr and 92-106 Mo isotope chains

    Spatial Pattern Formation in External Noise: Theory and Simulation

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    Spatial pattern formation in excitable fluctuating media was researched analytically from the point of view of the order parameters concept. The reaction-diffusion system in external noise is considered as a model of such medium. Stochastic equations for the unstable mode amplitudes (order parameters), dispersion equations for the unstable mode averaged amplitudes, and the Fokker-Planck equation for the order parameters have been obtained. The developed theory makes it possible to analyze different noise-induced effects, including the variation of boundaries of ordering and disordering phase transitions depending on the parameters of external noiseComment: 22 pages, 10 figure

    Pressure inequalities for nuclear and neutron matter

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    We prove several inequalities using lowest-order effective field theory for nucleons which give an upper bound on the pressure of asymmetric nuclear matter and neutron matter. We prove two types of inequalities, one based on convexity and another derived from shifting an auxiliary field.Comment: 16 pages, published journal version - includes inequalities for spin polarized system

    Fluctuation, Dissipation and the Arrow of Time

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    The recent development of the theory of fluctuation relations has led to new insights into the ever-lasting question of how irreversible behavior emerges from time-reversal symmetric microscopic dynamics. We provide an introduction to fluctuation relations, examine their relation to dissipation and discuss their impact on the arrow of time question.Comment: 12 pages, 3 figures. Minor Revisions. Accepted for publication in Entropy, Special Issue "Arrow of Time", edited by C. Callende
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