Perturbative Quantum (In)equivalence of Dual $\sigma$ Models in $2$ dimensions

Abstract

Various examples of target space duality transformations are investigated up to two loop order in perturbation theory. Our results show that when using the tree level (`naive') transformation rules the dual theories are in general {\it inequivalent} at two loops to the original ones, (both for the Abelian and the non Abelian duality).Comment: 11 pages, Latex, uses espcrc2.st