GREEN-FUNCTIONS FROM A GAUGE-INVARIANT EFFECTIVE ACTION FOR THE ELECTROWEAK STANDARD MODEL

Application of the background-field method to the electroweak Standard-Model yields a gauge-invariant effective action giving rise to simple Ward identities. We find that in the background-field 't Hooft-Feynman gauge the resulting vertex functions are exactly those that are obtained using the pinch technique. Thus, the background-field method provides a general framework that genealizes the pinch technique directly and uniquely to arbitrary Green functions and arbitrary orders of perturbation theory. Moreover, the desirable properties of the pinch-technique vertex functions hold for arbitrary guage parameters and have a simple explanation within the background-field method.