M. Dattanasio et Tr. Morris, GAUGE-INVARIANCE, THE QUANTUM ACTION PRINCIPLE, AND THE RENORMALIZATION-GROUP, Physics letters. Section B, 378(1-4), 1996, pp. 213-221
If the Wilsonian renormalization group (RG) is formulated with a cutof
f that breaks gauge invariance, then gauge invariance may be recovered
only once the cutoff is removed and only once a set of effective Ward
identities is imposed. We show that an effective quantum action princ
iple can be formulated in perturbation theory which enables the effect
ive Ward identities to be solved order by order, even if the theory re
quires nonvanishing subtraction points, The difficulties encountered w
ith nonperturbative approximations are briefly discussed.