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Regensburg 2000 – scientific programme

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DY: Dynamik und Statistische Physik

DY 17: POSTER I

DY 17.63: Poster

Monday, March 27, 2000, 15:00–18:00, D

Emergence of macroscopic non-equilibrium behaviour from microscopic dynamics in quantum spin chains — •G.M. Schütz1, T. Antal2, Z. Rácz2,3, and A. Rákos21Institut für Festkörperforschung, Forschungszentrum Jülich, 52425 Jülich, Germany — 2Institute for Theoretical Physics, Eötvös University, 1117 Budapest, Hungary — 3Institute for Solid State Physics, Hungarian Academy of Sciences, 1525 Budapest 114, Hungary

We study the time evolution of an inhomogeneous non-stationary quantum state of an isolated spin-1/2 XX quantum chain [1]. In the absence of a heat bath the dynamics are uniquely defined by the usual Schrödinger equation from which we obtain an exact expression for the evolving magnetization profile. In the classical limit (lattice constant and ℏ → 0, but spin=1/2 fixed) we obtain a scaling function which is a solution of the continuity equation ∂t m + ∂x j =0 corresponding to the conservation of magnetization in the XX-chain. The magnetization current j=j(m) is shown to be given by a selection principle based on a Lagrange-multiplier ansatz proposed earlier [T. Antal, Z. Rácz and L. Sasvári, PRL 78, 167 (1997)].
T. Antal, Z. Rácz, A. Rákos and G.M. Schütz, Phys. Rev. E 59, 4912 (1999).

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