  Conventional transport theory is not really applicable to non-equilibrium
systems which exhibit strong quantum effects. We present two different
approaches to overcome this problem. Firstly we point out how transport
equations may be derived that incorporate a nontrivial spectral function as a
typical quantum effect, and test this approach in a toy model of a strongly
interacting degenerate plasma. Secondly we explore a path to include
non-equilibrium effects into quantum field theory through momentum mixing
transformations in Fock space. Although the two approaches are completely
orthogonal, they lead to the same coherent conclusion.
