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DY: Fachverband Dynamik und Statistische Physik

DY 28: Statistical Physics far from Equilibrium

DY 28.9: Talk

Thursday, March 17, 2011, 12:30–12:45, HÜL 186

Analysis of non-equilibrium fluctuations of quantum mechanical expectation values — •Christian Bartsch and Jochen Gemmer — Fachbereich Physik, Universität Osnabrück, Barbarastrasse 7, D-49069 Osnabrück, Germany

For certain abstract, closed quantum systems the dynamics of expectation values, obtained by exact diagonalization, may be interpreted as a composition of some "regular" dynamics, e.g., an exponential decay into equilibrium, and some "irregular" part, which we call fluctuations. We numerically find that the latter may typically be regarded as Gaussian white noise in good approximation. Furthermore, we analyze particularly the non-equilibrium fluctuations on the basis of a Langevin-type equation describing the time evolution of the expectation value, where the fluctuations are incorporated as a stochastic force. We moreover define an entropy as a function of the analyzed expectation value, similar to the common von Neumann-entropy. As long as the fluctuations correspond to a stochastic Gaussian variable, the entropy production over time may as well be viewed as a Gaussian stochastic variable, for which then the fluctuation theorem holds. Additionally, we analyze the scaling of the fluctuations with fundamental system parameters.