The gauged nonlinear sigma model with Wess-Zumino term

The gauging of the isometry group of a general-two-dimensional nonlinear sigma model with Wess-Zumino term is investigated. In general, there is a topological obstruction to gauging, but this is absent for models which are invariant under a Kac-Moody symmetry. When there is no topological obstruction, any 'anomaly-free' subgroup of the isometry group can be gauged and we give a simple three-dimensional form of the gauged action. We show how the gauged Wess-Zumino-Novikov-Witten models arise as a particular case. Fermionization is discussed and supersymmetric extensions presented. (orig.)