Supergravity, Brane Dynamics and String Duality ‡

In this review we show that a Clifford algebra possesses a unique irreducible representation ; the spinor representation. We discuss what types of spinors can exist in Minkowski space-times and we explain how to construct all the supersymmetry algebras that contain a given space-time Lie algebra. After deriving the irreducible representations of the superymmetry algebras, we explain how to use them to systematically construct super-gravity theories. We give the maximally supersymmetric supergravity theories in ten and eleven dimensions and discuss their properties. We find which superbranes can exist for a given supersymmetry algebra and we give the dynamics of the superbranes that occur in M theory. Finally, we discuss how the properties of supergravity theories and superbranes provide evidence for string duality. In effect, we present a continuous chain of argument that begins with Clifford algebras and leads via supersymmetry algebras and their irreducible representations to supergravity theories, string duality, brane dynamics and M theory.