Atmospheric neutrino oscillations and maximal nu_mu-nu_tau mixing in unified models

Abstract

The recent data describing the evidence for neutrino oscillations by Super Kamiokande implies that two neutrinos are very strongly mixed. We ask the question: can approximate maximal neutrino mixing be natural in unified (GUT or string) models? We attempt to answer this question in as much generality as possible. Without specifying a particular model, we are able to show that a gauged family symmetry can naturally provide the required maximal mixing between mu and tau neutrinos. The second and third family neutrino mass eigenstates are almost degenerate with masses of order 0.2 eV.