title: Hierarchies from D-brane instantons in globally defined Calabi-Yau orientifolds.
abstract: We construct the first globally consistent semirealistic type I string vacua on an elliptically fibered manifold where the zero modes of the Euclidean D1-instanton sector allow for the generation of nonperturbative Majorana masses of an intermediate scale. In another class of global models, a D1-brane instanton can generate a Polonyi-type superpotential breaking supersymmetry at an exponentially suppressed scale.
authors.affiliation: Department of Physics and Astronomy, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA.
authors.forename: Mirjam
authors.initials: M
authors.lastname: Cvetic
authors.forename: Timo
authors.initials: T
authors.lastname: Weigand