RECONCILING DARK-MATTER, SOLAR AND ATMOSPHERIC NEUTRINOS

We present models that can reconcile the solar and atmospheric neutrino data with the existence of a hot dark matter component in the universe. This dark matter is a quasi-Dirac neutrino whose mass m(DM) arises at the one-loop level. The solar neutrino deficit is explained via nonadiabatic conversions of nu(e) to a sterile neutrino nu(s) and the atmospheric neutrino data via maximal nu(mu) to nu(tau) oscillations generated by higher order loop diagrams. For m(DM) approximately 30 eV the radiative neutrino decay can lead to photons that can ionize interstellar hydrogen. In one of the models one can have observable nu(e) to nu(tau) oscillation rates, with no appreciable nu(mu) oscillations at accelerator experiments. In addition, there can be observable rates for tau number violating processes such as tau --> 3e and tau --> e+ gamma. In the other model one can have sizeable nu(e) to nu(mu) oscillation rates, as well as sizeable rates for muon number violating processes such as mu --> e+ gamma, mu --> e+ majoron and mu --> 3e.