U-duality of Born-Infeld on the noncommutative two-torus

Abstract

We discuss Born-Infeld on the noncomm utativ e two-torus as a description of compactified string theory. We show that the resulting theory, including the uctuations, is manifestly invariant under the T-duality group SO(2; 2; Z ). The BPS mass ev en has a full SL(3; Z ) x SL(2; Z ) U-duality symmetry . The direct identification of the noncomm utative parameter Ø with the B-field modulus ho wever seems to be problematic at finite v olume.