STRING THEORY DUALITIES FROM M-THEORY

We analyze how string theory dualities may be described in M-theory. T -dualities arise from scalar-vector dualities in the worldvolume of th e membrane of M-theory. ''Electric-magnetic'' dualities arise from a d uality transformation in M-theory compactified on a 3-torus, which tak es the membrane into a fivebrane wrapped around the 3-torus. We show h ow the action of the membrane transforms into the action of the wrappe d fivebrane by this transformation. Other ''electric-magnetic'' dualit ies are related to this duality by compactifications and orbifoldings.