M and F theory instantons, N=1 supersymmetry and fractional topological charge

Abstract

We analize instanton generated superpotentials for three dimensional N = 2 supersymmetric gauge theories obtained by compactifying on S^(1) N = 1 four dimensional theories. For SU(2) with N_(f) = 1, we find that the vacua in the decompactification limit is given by the singular points of the Coulomb branch of the N = 2 four dimensional theory (we also consider the massive case). The decompactification limit of the superpotential for pure gauge theories without chiral matter is interpreted in terms of ‘t Hooft’s fractional instanton amplitudes.