Renormalized kinetic equations for a system with weak interaction and for a low-density gas

The collision integrals in the Fokker–Planck and Boltzmann equations are renormalized. The renormalized collision integrals take into account the influence of the “medium” on two-particle collisions, this giving rise to a natural cutoff of the correlation functions at times and lengths of the order of the mean free time and the mean free path, respectively, of the molecules.