WORLD-BRANE ACTIONS OF SUPERSTRING SOLITONS AND DUALITY

In this talk it is reviewed how effective world-brane actions of solit ons of ten-dimensional type IIA and IIB superstring theory can be deri ved by using the formulation of solitons as Dirichlet branes. In parti cular, it is shown how the one-brane actions one obtains confirm the p redictions of SL(2, Z) strong-weak coupling duality. It is also shown how the two-brane action, which contains a hidden eleventh target spac e coordinate, turns out to be the Bergshoeff-Sezgin-Townsend supermemb rane action.