Mirror symmetry for open strings - art. no. 126005

We discuss the generation of superpotentials in d=4, N=1 supersymmetric fie ld theories arising from type-IIA D6-branes wrapped on supersymmetric three -cycles of a Calabi-Yau threefold. In general, nontrivial superpotentials a rise from sums over disc instantons. We then find several examples of speci al Lagrangian three-cycles with nontrivial topology which are mirror to obs tructed rational curves, conclusively demonstrating the existence of such i nstanton effects. In addition, we present explicit examples of disc instant ons ending on the relevant three-cycles. Finally, we give a preliminary con struction of a mirror map for the open string moduli, in a large-radius lim it of the type IIA compactification.