Wilsonian renormalization group and the non-commutative IR/UV connection

We study the IR/UV connection of the four-dimensional non-commutative phi ( 4) theory by using the wilsonian Renormalization Group. Extending the usual formulation to the non-commutative case we are able to prove UV renormaliz ability to all orders in perturbation theory. The full RG equations are fin ite in the IR, but perturbative approximations of them are plagued by IR di vergences. The latter can be systematically resummed in a way analogous to what is done in finite temperature field theory. As an application, next-to -leading order corrections to the two-point function are explicitly compute d. The usual wilsonian picture, i.e. the insensitivity of the IR regime to the UV, does not hold in the non-commutative case. Nevertheless it can be p artially recovered by a matching procedure, in which a high-energy theory, defined in the deep non-commutative regime, is connected at some intermedia te scale to a commutative low-energy theory. The latter knows about non-com mutativity only through the boundary conditions for two would-be irrelevant couplings.