Neutrinos in supernovae and extra dimensions

A neutrino mass-mixing scheme which explains qualitatively all present evidence for neutrino mass (the solar and atmospheric neutrino deficits, LSND, and significant hot dark matter) also successfully avoids the "alpha effect", allowing r-process nucleosynthesis in the neutrino-heated ejecta of supernovae. The properties of neutrinos required to ensure production of heavy nuclei provides independent evidence for (1) at least one light sterile neutrino, upsilon (a); (2) a near maximally-mixed upsilon (mu)-upsilon (tau) doublet (which also explains the atmospheric anomaly and provides hot dark matter) split from a lower mass upsilon (e)-upsilon (s) doublet (needed also for the solar upsilon (e) deficit); (3) upsilon (mu)-upsilon (e) mixing greater than or similar to 10(-4); and (4) a splitting between the doublets (measured by the upsilon (mu)-upsilon (e) mass difference) greater than or similar to 1 eV(2), favoring the upper part of the LSND range. There is a quantitative problem with the solar observations, which do not in detail fit this or any other model. If, however, the upsilon (s) is a bulk neutrino in extra dimensions the nearness in mass of the zero mode to the upsilon (e) provides vacuum oscillations, while the Kaluza-Klein states give MSW oscillations, and all the solar data can be fit.