A New Approach to Axial Vector Model Calculations
  We consider the one-loop effective action due to a spinor loop coupled to an abelian vector and axial vector field background. After rewriting this effective action in terms of an auxiliary non-abelian gauge connection, we use the De Witt expansion to analyze both its anomalous and non-anomalous content. The same transformation allows us to obtain a novel worldline path integral representation for this effective action which avoids the usual separation into the real and imaginary parts of the Euclidean effective action, as well as the introduction of auxiliary dimensions. 
D.G.C. McKeon, C. Schubert