Volume 88, Number 1, October 2009
|Number of page(s)||5|
|Published online||22 October 2009|
Density dynamics from current auto-correlations at finite time- and length-scales
Fachbereich Physik, Universität Osnabrück - Barbarastrasse 7, D-49069 Osnabrück, Germany, EU
Corresponding author: email@example.com
Accepted: 17 September 2009
We consider the increase of the spatial variance of some inhomogeneous, non-equilibrium density (particles, energy, etc.) in a periodic quantum system of condensed-matter type. This is done for a certain class of initial quantum states which is supported by static linear response and typicality arguments. We directly relate the broadening to some current auto-correlation function at finite times. Our result is not limited to diffusive behavior, however, in that case it yields a generalized Einstein relation. These findings facilitate the approximation of diffusion constants/conductivities on the basis of current auto-correlation functions at finite times for finite systems. Pursuing this, we quantitatively confirm the magnetization diffusion constant in a spin chain which was recently found from non-equilibrium bath scenarios.
PACS: 05.60.Gg – Quantum transport / 05.30.-d – Quantum statistical mechanics / 05.70.Ln – Nonequilibrium and irreversible thermodynamics
© EPLA, 2009
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