DUALITY IN THE TYPE-II SUPERSTRING EFFECTIVE ACTION

We derive the T-duality transformations that transform a general d = 10 solution of the type IIA string with one isometry to a solution of the type-IIB string with one isometry and vice versa. In contrast to other superstring theories, the T-duality transformations are not related to a non-compact symmetry of a d = 9 supergravity theory. We also discuss S-duality in d = 9 and d = 10 and the relationship with eleven-dimensional supergravity theory. We apply these dualities to generate new solutions of the type-IIA and type-IIB superstrings and of eleven-dimensional supergravity.