Regensburg 2000 – wissenschaftliches Programm
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DY: Dynamik und Statistische Physik
DY 17: POSTER I
DY 17.63: Poster
Montag, 27. März 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. Rákos2 — 1Institut 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).