Dyson-schwinger equations in quantum electrodynamics: the non-pertubative approximation of salam and delbourgo

A quantum field theory is completely determined by the knowledge of its Green functions. A Green function is the vacuum expectation value of the time-ordered product of a set of field operators. The field theory that will be mostly considered here will be quantum electrodynamics, which is the quantum- mechanical formulation of electrodynamics, describing the interaction between photons and electrons (and positrons). If (in the Heisenberg picture) the electron field is represented by the spinor field operator, O(x), and the photon field by the quantized vector potential or vector field, Au(x) ... Zie: Introduction and summary