Some aspects of microreversibility for open systems

It is verified that microreversibility conditions for higher order correlation functions for a classical or quantum markovian system are satisfied if they hold for second order correlation functions. The phase space version of the conditions is given. It is found that in this formulation the distribution function and Green's function for a given ordering mix with those for inverse ordering. We display explicitly the terms arising due to non-com-mutativity of operators for the Weyl ordering. Finally the microreversibility conditions are used to calculate the stationary solution of the master equation describingn photon absorption and emission.