1,979 research outputs found

    A Generalized Circle Theorem on Zeros of Partition Function at Asymmetric First Order Transitions

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    We present a generalized circle theorem which includes the Lee-Yang theorem for symmetric transitions as a special case. It is found that zeros of the partition function can be written in terms of discontinuities in the derivatives of the free energy. For asymmetric transitions, the locus of the zeros is tangent to the unit circle at the positive real axis in the thermodynamic limit. For finite-size systems, they lie off the unit circle if the partition functions of the two phases are added up with unequal prefactors. This conclusion is substantiated by explicit calculation of zeros of the partition function for the Blume-Capel model near and at the triple line at low temperatures.Comment: 10 pages, RevTeX. To be published in PRL. 3 Figures will be sent upon reques

    Yield Strength Analysis by Small Punch Test Using Inverse Finite Element Method

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    AbstractConsidering the change of material behavior in in-service component due to temperature, loading and irradiation, several micro-specimen techniques have been proposed to describe deformation and fracture behaviors of materials under different conditions. This paper investigates the mechanical characterization of materials by the experimental and numerical method of small punch test. A two-dimensional finite element model was established to simulate the deformation behavior of X80. The resulting Load-Displacement curve contains key information about the mechanical properties of the tested materials. Thus, an application of inverse finite element method was used in the investigation of mechanical properties of materials which have been tested by small punch test. The difference between experiment and simulation curves was defined as objective function based upon the calculation model established by ABAQUS and MATLAB procedure. Finally, the estimated results suggested confidence in the analysis of the inverse finite element method for material's yield strength

    Spin-Hall effect with quantum group symmetry

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    We construct a model of spin-Hall effect on a noncommutative 4 sphere with isospin degrees of freedom (coming from a noncommutative instanton) and invariance under a quantum orthogonal group. The corresponding representation theory allows to explicitly diagonalize the Hamiltonian and construct the ground state; there are both integer and fractional excitations. Similar models exist on higher dimensional noncommutative spheres and noncommutative projective spaces.Comment: v2: 14 pages, latex. Several changes and additional material; two extra sections added. To appear in LMP. Dedicated to Rafael Sorkin with friendship and respec

    Exact Zeros of the Partition Function for a Continuum System with Double Gaussian Peaks

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    We calculate the exact zeros of the partition function for a continuum system where the probability distribution for the order parameter is given by two asymmetric Gaussian peaks. When the positions of the two peaks coincide, the two separate loci of zeros which used to give first-order transition touch each other, with density of zeros vanishing at the contact point on the positive real axis. Instead of the second-order transition of Ehrenfast classification as one might naively expect, one finds a critical behavior in this limit.Comment: 13 pages, 6 figures, revtex, minor changes in fig.2, to be published in Physical Review

    Nondissipative Drag Conductance as a Topological Quantum Number

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    We show in this paper that the boundary condition averaged nondissipative drag conductance of two coupled mesoscopic rings with no tunneling, evaluated in a particular many-particle eigenstate, is a topological invariant characterized by a Chern integer. Physical implications of this observation are discussed.Comment: 4 pages, no figure. Title modified and significant revision made to the text. Final version appeared in PR

    Quantum Locality

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    It is argued that while quantum mechanics contains nonlocal or entangled states, the instantaneous or nonlocal influences sometimes thought to be present due to violations of Bell inequalities in fact arise from mistaken attempts to apply classical concepts and introduce probabilities in a manner inconsistent with the Hilbert space structure of standard quantum mechanics. Instead, Einstein locality is a valid quantum principle: objective properties of individual quantum systems do not change when something is done to another noninteracting system. There is no reason to suspect any conflict between quantum theory and special relativity.Comment: Introduction has been revised, references added, minor corrections elsewhere. To appear in Foundations of Physic

    Singularites at a Dense Set of Temperature in Husimi Tree

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    We investigate complex temperature singularities of the three-site interacting Ising model on the Husimi tree in the presentce of magnetic field. We show that at certain magnetic field these singularities lie at a dense set and as a consequence the phase transition condensation take place.Comment: ps file, 10 page

    Numerical Test of Disk Trial Wave function for Half-Filled Landau Level

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    The analyticity of the lowest Landau level wave functions and the relation between filling factor and the total angular momentum severely limits the possible forms of trial wave functions of a disk of electrons subject to a strong perpendicular magnetic field. For N, the number of electrons, up to 12 we have tested these disk trial wave functions for the half filled Landau level using Monte Carlo and exact diagonalization methods. The agreement between the results for the occupation numbers and ground state energies obtained from these two methods is excellent. We have also compared the profile of the occupation number near the edge with that obtained from a field-theoretical method. The results give qualitatively identical edge profiles. Experimental consequences are briefly discussed.Comment: To be published in Phys. Rev. B. 9 pages, 6 figure

    Susceptibility of the Spin 1/2 Heisenberg Antiferromagnetic Chain

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    Highly accurate results are presented for the susceptibility, χ(T)\chi (T) of the s=1/2s=1/2 Heisenberg antiferromagnetic chain for all temperatures, using the Bethe ansatz and field theory methods. After going through a rounded peak, χ(T)\chi (T) approaches its asympotic zero-temperature value with infinite slope.Comment: 8 pages and 3 postscript figures appended (uuencoded), Revtex, Report #:UBCTP-94-00

    Thermodynamical Bethe Ansatz and Condensed Matter

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    The basics of the thermodynamic Bethe ansatz equation are given. The simplest case is repulsive delta function bosons, the thermodynamic equation contains only one unknown function. We also treat the XXX model with spin 1/2 and the XXZ model and the XYZ model. This method is very useful for the investigation of the low temperature thermodynamics of solvable systems.Comment: 52 pages, 6 figures, latex, lamuphys.st
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