QUANTUM CORRECTIONS OF ABELIAN DUALITY TRANSFORMATIONS IN SIGMA-MODELS

A review is given of a recently proposed modification of the Abelian D uality transformations guaranteeing that a (not necessarily conformall y invariant) a-model be quantum equivalent (at least up to two loops i n perturbation theory) to its dual. This requires a somewhat non stand ard perturbative treatment of the dual sigma-model. Explicit formulae of the modified duality transformation are presented for a special cla ss of block diagonal purely metric sigma-models.