Stringy origin of neutrino masses within the minimal supersymmetric standard model

We present a ''gravity-induced'' seesaw mechanism, which accommodates neutrino masses (mν∝m2u/MI, with mu the corresponding quark mass and MI congruent 4x1011 GeV) compatible with the MSW study of the Solar neutrino deficit within the minimal supersymmetric Standard Model (the grand desert with the gauge coupling unification at MU congruent 2x1016 GeV). We show that for large radius (R2/α'=O(20)) Calabi-Yau spaces, threshold corrections ensure M2U=M2C/O(2R2/α') and the magnitude of the non-renormalizable terms in the superpotential yields MI=O(e-R2/α')MC. Here MC=gx5.2x1017 GeV is the scale of the tree level (genus zero) gauge coupling (g) unification