Holomorphic Corrections from Wrapped Euclidean Branes

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 from 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. This note is based on [R. Argurio, M. Bertolini, G. Ferretti, A. Lerda and C. Petersson, JHEP 0706, 067 (2007) [arXiv:0704.0262 [hep-th]]; G. Ferretti and C. Petersson, arXiv:0901.1182 [hep-th]].