A recently proposed approximation method, called the $\delta$ 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 $\delta$-expansion methods to field theories having local gauge symmetry. We then compute the anomaly in the Schwinger model.

• Received 13 April 1989

DOI:https://doi.org/10.1103/PhysRevD.40.1354