Diagram Expansions in Nonequilibrium Statistical Mechanics Classical Limit Considerations

A diagram expansion is proposed for calculating traces of the kind Tr{Ae^?itLB} which are of interest for calculating time correlation functions and expectation values in nonequilibrium statistical mechanics. Arbitrary initial conditions are considered. In the classical limit the diagram expansion of FUJITA is obtained. A systematic method for obtaining quantum corrections including exchange and symmetry effects is proposed.