Multi-time correlations in relaxing quantum dynamical systems
  In this paper, we consider the long time asymptotics of multi-time correlation functions for quantum dynamical systems that are sufficiently random to relax to a ``reference state''. In particular, the evolution of such systems must have a continuous spectrum. Special attention is paid to general dynamical clustering conditions and their consequences for the structure of fluctuations of temporal averages. 
J. Andries, F. Benatti, M. De Cock, M. Fannes