Instanton-induced amplitudes in a supersymmetric theory

We consider the effective lagrangian for multiple self-interaction of matter fields induced by instantons in a weakly coupled SU (2) supersymmetric Yang-Mills theory with one matter flavor. By using the supersymmetric instanton calculus, we come to the surprising conclusion that the interaction induced by instantons in the one instanton sector of the theory is strictly local for scalar particle emission, accompanied by fermion number violation. The contribution of instantons arises only from instantons of zero scale size. The restoration of unitarity in high-energy scattering is thus only possible through multi-instanton-antiinstanton effects.