Supergravity and theSmatrix

Abstract

We discuss supergravity from an $S$-matrix point of view. Kinematical constraints on helicity amplitudes determine the spin-2 and spin-3/2 Born amplitudes almost uniquely, and force Born amplitudes involving spin-5/2 fermions to vanish. Global supersymmetry is then used to determine the Born amplitudes completely. We suggest that Lorentz invariance, presence of only one (dimensional) coupling constant $\kappa$, and global supersymmetry lead to a unique locally supergauge-invariant theory of spin-2 and spin-3/2 particles. We draw similar conclusions for a model uniting supergravity and the Wess-Zumino scalar multiplet.