On the foundation of equilibrium quantum statistical mechanics
  We discuss the condition for the validity of equilibrium quantum statistical mechanics in the light of recent developments in the understanding of classical and quantum chaotic motion. In particular, the ergodicity parameter is shown to provide the conditions under which quantum statistical distributions can be derived from the quantum dynamics of a classical ergodic Hamiltonian system. 
Giulio Casati (International Center for the Study of Dynamical   Systems, Como, Italy Istituto Nazionale di Fisica della Mat...