Nonequilibrium Two-Particle Dyson Equation

The two-particle problem within a nonequilibrium many-particle system is investigated in the framework of real-time Greenʹs functions. A nonequilibrium Dyson equation is given for the two-time two-particle Greenʹs function. The two-particle self-energy in this equation consists of two qualitatively different parts: one part is local in time, whereas the other part is a two-time quantity having thus a dynamical character. The latter part of the self-energy can be expressed in terms of multi-particle Greenʹs functions.