Duality, marginal perturbations, and gauging.

We study duality transformations for two-dimensional sigma models with abelian chiral isometries and prove that generic such transformations are equivalent to integrated marginal perturbations by bilinears in the chiral currents, thus confirming a recent conjecture by Hassan and Sen formulated in the context of Wess-Zumino-Witten models. Specific duality transformations instead give rise to coset models plus free bosons. ⋆ Research supported by the Swedish Natural Science Research Council (NFR). † Research supported in part by the Ambrose Monell Foundation.