SO(10) GRAND UNIFICATION MODEL FOR DEGENERATE NEUTRINO MASSES

We propose an SO(10) scheme where neutrino masses can simultaneously e xplain the solar and atmospheric neutrino deficits, together with a ho t dark matter component. In our scheme the nu(e), nu(mu), and nu(tau) are approximately degenerate with a mass of about 2 eV, which can lead to an observable neutrinoless double beta decay rate. The model is ba sed on a realization of the seesaw mechanism in which the main contrib ution to the light neutrino masses is universal, due to a suitable SU( 2) horizontal symmetry, while the splittings between nu(e) and nu(mu) explain the solar neutrino deficit and that between nu(mu) and nu(tau) explain the atmospheric neutrino anomaly.