Kinetic equations for quantum subsystems with finite number of degrees of freedom in a condensed medium

Quantum subsystems with a finite number of degrees of freedom when the interaction of the subsystem with the thermal bath is linear in the creation and annihilation operators of the vibrations in the thermal bath are considered and a perturbation theory formalism proposed which enables one in the framework of the nonequilibrium density matrix method to obtain kinetic equations for the parameters of the quantum subsystems.