Dyson–Schwinger equation for a system of two particles in quantum electrodynamics

The Dyson–Schwinger type representation for the kernel of the Bethe–Salpeter equation is derived. This representation makes it possible to perform the partial summation of irreducible diagrams which is necessary e.g. in the presence of two-particle bound states in quantum electrodynamics. The approximate expression for the kernel taking into account the effects of binding is constructed.