Onset of Fokker-Planck dynamics within a closed finite spin system

Abstract

Relaxation according to Fokker-Planck equations is a standard scenario in classical statistical mechanics. It is, however, not obvious how such a Fokker-Planck dynamics may emerge within a closed, finite quantum system. We present an analysis of a system comprising sixteen spins in which spatial inhomogeneities of the magnetization relax approximately in accord with a standard Fokker-Planck equation for a Brownian particle in a parabolic potential. While a single, specfic example is addressed in detail, arguments which indicate that the above findings may hold for a wider range of systems are given. Copyright (C) EPLA, 2013