The delta expansion and local gauge invariance.

Abstract

A recently proposed approximation method, called the $\ensuremath{\delta}$ expansion, was introduced in the context of a self-interacting scalar field theory. This approximation method offers the hope of obtaining nonperturbative information about a quantum field theory using perturbative techniques. In this paper we extend formally the $\ensuremath{\delta}$-expansion methods to field theories having local gauge symmetry. We then compute the anomaly in the Schwinger model.