Theory of quantum relativistic kinetic equations

The Tomonaga–Schwinger equation is used to obtain a quantum Liouville equation in a relativistically invariant form. The derivation of the system of kinetic equations for a quantum relativistic system consisting of several species of charged fermions interacting through the electromagnetic field is considered as an example. The calculations are made to second order in the coupling constant. It is shown that external fields are absent and the system is quasihomogeneous.