Generalized kinetic equation for a dynamical system interacting with a phonon field

Derivation of the kinetic equation proposed in the paper [1] is generalised and methods of studying the electron-phonon system and excluding phonon operators from corresponding kinetic equation are formulated. In particular, the polaron kinetic equation is obtained for the interaction of the electron with the phonon field. If a certain approximation is made in this equation, it implies, for instance, the exact Boltzmann equation for the polaron.