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Q: Quantenoptik und Photonik

Q 2: Quantengase I

Q 2.6: Talk

Monday, March 13, 2006, 12:25–12:40, HVI

Dynamics of an ultracold quantum gas far from equilibrium — •Thomas Gasenzer, Jürgen Berges, Michael Schmidt, and Marcos Seco — Institut für Theoretische Physik, Philosophenweg 16, 69120 Heidelberg

A full quantum many-body theoretical study of the equilibration process of an ultracold Bose gas, initially in a state far away from equilibrium, is presented. In more and more experimental situations, ultracold atomic Bose and Fermi gases are driven far away from a thermal equilibrium state. Magnetic and optical Feshbach resonances as well as sophisticated trapping techniques play an important role in this progress. Precise measurements of the ensuing dynamics have become possible which have the potential for important impact in various areas of physics. The far-from equilibrium configurations of particular interest are those where quantum fluctuations become important which are not taken into account in mean-field theory. An approach to beyond-mean-field quantum many-body theory on the basis of Green-function techniques is presented. This allows to describe both the short and long-time evolution of a gas far from equilibrium. The dynamical many-body theory remains applicable at long times, where thermal equilibrium is approached. This is shown for the example of a weakly interacting one-dimensional Bose gas. The method allows to distinguish quantum and classical aspects of the dynamical evolution.