Holomorphic corrections from wrapped Euclidean branes

Paper in proceeding, 2009

We discuss how non-perturbative corrections to the four-dimensional effective superpotential are generated by wrapped Euclidean D-branes. It is shown how such terms can be computed and we give a few examples of holomorphic couplings that arise front a D-brane instanton effect in string theory. Some of these instanton configurations give rise to phenomenologically desirable couplings although they do not admit an obvious interpretation in terms of standard gauge theory.