Neutrino mixings and fermion masses in supersymmetric SU(5)

We consider neutrino mixings in supersymmetric SU(5) supplemented by a U(1) flavor symmetry. In particular, we show how bi-maximal neutrino mixings can be realized. Two scenarios for implementing the small mixing angle MSW solution, with one involving a sterile state νs and maximal νμ−νs mixing to resolve the atmospheric anomaly, are also discussed. Finally, a new mechanism for eliminating the asymptotic relations m(0)μ=m(0)s and m(0)e=m(0)d, while retaining m(0)τ=m(0)b, is presented. It employs `matterʹ multiplets in the 15+15 of SU(5), and is consistent with the various oscillation scenarios, as well as with the unification at MGUT of the three gauge couplings.