A renormalization prescription for massless quantum electrodynamics

An alternative proof of the Ward-Takahashi identity for perturbative quantum electrodynamics is given which makes no use of a gauge invariant regularization such as the Pauli-Villars loop subtraction or dimensional regularization. Instead, it is shown, in the presence of an arbitrary high momentum cutoff, that the exact W-T identity holds with an error ofO(1) with 0<<1. The proof involves a perturbative analysis of the Euclidean functional integral for QED by the tree expansion method.Research supported by the Natural Sciences and Engineering Research Council