Analytic equivalence of the Gupta-Bleuler formalism and of anS-matrix formalism for processes involving photons

Abstract

This paper studies the equivalence of the analyticity properties whether formulated in anS-matrix formalism introduced by Zwanziger or in the usual quantum electrodynamical formalism. Although the description of the photon appears completely different in these two formalisms, the mentioned equivalence is established for interactions of a single photon with hadrons, with exception of the case where the hadrons interact with magnetic monopoles.