TYPE-IIB-STRING-M-THEORY DUALITY AND LONGITUDINAL MEMBRANES IN M(ATRIX) THEORY

In this paper we study duality properties of the M(atrix) theory compa ctified on a circle. We present evidence for the equivalence of this t heory to the strong coupling limit of type-IIB string theory compactif ied on a circle. In the M(atrix) theory context, our evidence for this duality consists of showing the appearance (upon compactification) of a topological term recently discovered in the D-string action, identi fying the BPS states of type-IIB strings in the spectrum and finding t he remnant symmetry of SL(2,Z) and the associated tau moduli. By this type-IIB-string-M-theory duality, a number of insights are gained into the physics of longitudinal membranes in the infinite momentum frame. [S0556-2821(97)05622-1].