PERTURBATIVE INFRARED FINITENESS OF YANG-MILLS THEORY FROM RENORMALIZATION-GROUP FLOW

It is commonly believed that a Yang-Mills theory (and in general a massless theory) with a nonvanishing subtraction point is infrared finite, i.e. the vertex functions at non-exceptional momenta are finite. We give a simple perturbative proof of this fact by using the Wilson renormalization group formulation. The proof requires the control of the singular behaviour of vertex functions only for a restricted class of exceptional configurations of momenta.