Wilsonian Flow and Mass-independent Renormalization

We derive the Gell-Mann and Low renormalization group equation in the Wilsonian approach to renormalization of massless gφ in four dimensions, as a particular case of a non-linear equation satisfied at any scale by the Wilsonian effective action. We give an exact expression for the β and γφ functions in terms of the Wilsonian effective action at the Wilsonian renormalization scale ΛR; at the first two loops they are simply related to the gradient of the flow of the relevant couplings and have the standard values; beyond two loops this relation is spoilt by corrections due to irrelevant couplings. We generalize this analysis to the case of massive gφ, introducing a massindependent Wilsonian renormalization scheme; using the flow equation technique we prove renormalizability and we show that the limit of vanishing mass parameter exists. We derive the corresponding renormalization group equation, in which β and γφ are the same as in the massless case; γm is also mass-independent; at one loop it is the gradient of a relevant coupling and it has the expected value. Work supported in part by M.U.R.S.T.