BRS SYMMETRY FOR YANG-MILLS THEORY WITH EXACT RENORMALIZATION-GROUP

In the exact renormalization-group (RG) flow in the infrared cutoff La mbda one needs boundary conditions, In a previous paper on SU(2) Yang- Mills theory we proposed to use the nine physical relevant couplings o f the effective action as boundary conditions at the physical point La mbda = 0 (these couplings are defined at some non-vanishing subtractio n point mu not equal 0). In this paper we show perturbatively that it is possible to appropriately fix these couplings in such a way that th e full set of Slavnov-Taylor (ST) identities are satisfied. Three coup lings are given by the vector and ghost wave-function normalization an d the three-vector coupling at the subtraction point; three of the rem aining six are vanishing (e.g. the vector mass) and the others are exp ressed by irrelevant vertices evaluated at the subtraction point. We f ollow the method used by Becchi to prove ST identities in the RG frame work. There the boundary conditions are given at a non-physical point Lambda = Lambda' not equal 0, so that one avoids the need of a non-van ishing subtraction point.