The unitarity problem and the zero-mass limit for a model of massive yang-mills theory

Abstract

In a previous paper we proposed a Lagrangian model for a massive Yang-Mills field. This model exhibits invariance under the Slavnov transformations proposed by Becchi, Rouet and Stora. This invariance implies the Slavnov-Taylor identities. Here we study the problem of unitarity and gauge invariance. For a massless field one can prove physical unitarity and gauge invariance at the formal level,i.e. by ignoring infra-red problems. Form≠0 theS-matrix is not unitary and gauge invariant, when restricted to the physical subspace. We show how these properties are restored in the limit of zero mass.