SOLUTION-GENERATING TRANSFORMATIONS AND THE STRING EFFECTIVE ACTION

We study exhaustively the solution-generating transformations (dualiti es) that occur in the context of the low-energy effective action of su perstring theory. We first consider target-space duality ('T duality') transformations in the absence of vector fields. We find that for one isometry the full duality group is (SO up arrow(1, 1))(3) x D-4, the discrete part (D-4) being non-Abelian. We then include non-Abelian Yan g-Mills fields and find the corresponding generalization of the T dual ity transformations. We study the alpha' corrections to these transfor mations and show that the T duality rules are considerably simplified if the gauge group is embedded in the holonomy group. Next, in the cas e in which there are Abelian vector fields, we consider the duality gr oup that includes the transformation, introduced by Sen, that rotates among themselves the components of the metric, axion and vector field. Finally we list the duality symmetries of the type II theories with o ne isometry.