Spectral Representation for Elastic Photon-Photon Scattering

Abstract

The derivation of spectral forms in source theory has recently been systematically developed for systems of scalar particles. Elastic photon-photon scattering in lowest nonvanishing order is here studied as a simple, but representative, example of the additional considerations necessitated by particles having internal quantum numbers. The amplitude is determined as a double-spectral form augmented by a single-spectral one, the latter being related to the imposition of gauge invariance. Also presented is some discussion on how, in source theory, one obtains at given order all the contributions to the amplitude.