Interactions and Feynman Diagrams

J. Schirmer

Michael Rudolf Vogl

Michele Fabrizio

Lev Sakhnovich

In this note, we formulate the notions of the direct and inverse problems and contact points for the Feynman diagrams. For the electron-photon interaction case, the solutions of these direct and inverse problems are presented. The interrelations between Feynman diagrams and the classical colored graphs are discussed.

D. J. Kim

Henrik Bruus, Karsten Flensberg

Abstract It is in the case of interacting particles and fields that the power of quantum field theory and Feynman diagrams really comes into play. In this chapter, we develop the Feynman diagram technique for a system of fermions with pair interactions. The primary example we will work with is a gas of fermions interacting through Coulomb interactions, but the technique is derived in a more general framework. In general, the Hamiltonian has two parts H = H 0 + W .