Gauge (in)dependence, nonlocal counterterms and extended BRST-symmetry. A pedagogical example

Abstract

For n 2≠0 a generalized Leibbrandt-Mandelstam (LM) prescription is used to analyze the one-loop counterterms of ordinary QED. Using a recently proposed form of the gauge fixing where n μ and its dual vector n ∗μ are present already at the classical level allows to formulate an extended BRST symmetry involving also the variations of the gauge parameters n μ and n ∗μ into Grassmann variables χ μ and χ ∗μ .