N = 1 dual string pairs and their massless spectra

Abstract We construct two chains of four-dimensional F-theory/heterotic dual string pairs with N = 1 supersymmetry. On the F-theory side as well as on the heterotic side the geometry of the involved manifolds relies on del Pezzo surfaces. We match the massless spectra by using, for one chain of models, an index formula to count the heterotic bundle moduli and determine the dual F-theory spectra from the Hodge numbers of the four-folds X 4 and of the type 1113 base spaces.