A perfect match of MSSM-like orbifold and resolution models via   anomalies
  Compactification of the heterotic string on toroidal orbifolds is a promising set-up for the construction of realistic unified models of particle physics. The target space dynamics of such models, however, drives them slightly away from the orbifold point in moduli space. This resolves curvature singularities, but makes the string computations very difficult. On these smooth manifolds we have to rely on an effective supergravity approximation in the large volume limit. By comparing an orbifold example with its blow-up version, we try to transfer the computational power of the orbifold to the smooth manifold. Using local properties, we establish a perfect map of the the chiral spectra as well as the (local) anomalies of these models. A key element in this discussion is the Green-Schwarz anomaly polynomial. It allows us to identify those redefinitions of chiral fields and localized axions in the blow-up process which are relevant for the interactions (such as Yukawa-couplings) in the model on the smooth space. 
Michael Blaszczyk, Nana Geraldine Cabo Bizet, Hans Peter Nilles,   Fabian Ruehle
hep-th hep-ph