In this series of lectures we present the universal method based on the use of the functional integrals to derive the bound state equations for different two-body systems in elementary particle physics as well as in condensed matter theory: the relativistic Nambu-Jona-Lasinio equation and the relativistic Bethe-Salpeter equation in elementary particle physics, the Bethe-Salpeter equation for the bipolaritons. The bound state equation for the three-body systems is also established.
Categories: hep-ph