Conformal and non-conformal symmetries in 2D dilaton gravity

We introduce new extra symmetry transformations for generic 2D dilaton-gravity models, These symmetries are nonconformal but special linear combinations of them rum out to be the extra (conformal) symmetries of the CGHS model and the model with an exponential potential, We show that one of the non-conformal extra symmetries can be converted into a conformal one by means of adequate field redefinitions involving the metric and the derivatives of the dilaton. Finally, by expressing the Polyakov-Liouville effective action in terms of an auxiliary invariant metric, we construct one-loop models which maintain the extra symmetry of the classical action. (C) 1997 Elsevier Science B.V.