Convergence of the quantum Boltzmann map

We consider a non-linear map on the space of density matrices, which we call the Boltzmann map . It is the composition of a doubly stochastic mapT on the space ofn-body states, and the conditional expectation onto the one-body space. WhenT is ergodic, then the iterates of take any initial state to the uniform distribution. If the energy levels are equally spaced, andT conserves energy and is ergodic on each energy shell, then iterates of take any initial state of finite energy to a canonical distribution.