title: Quantum chaos and effective thermalization.
abstract: We demonstrate effective equilibration for unitary quantum dynamics under conditions of classical chaos. Focusing on the paradigmatic example of the Dicke model, we show how a constructive description of the thermalization process is facilitated by the Glauber Q or Husimi function, for which the evolution equation turns out to be of Fokker-Planck type. The equation describes a competition of classical drift and quantum diffusion in contractive and expansive directions. By this mechanism the system follows a "quantum smoothened" approach to equilibrium, which avoids the notorious singularities inherent to classical chaotic flows.
authors.affiliation: Institut für Theoretische Physik, Universität zu Köln, Köln, Germany.
authors.forename: Alexander
authors.initials: A
authors.lastname: Altland
authors.forename: Fritz
authors.initials: F
authors.lastname: Haake