Double threefold degeneracies for active and sterile neutrinos

Abstract

We explore the possibility that the three active (doublet) neutrinos have nearly degenerate masses which are split only by the usual seesaw mechanism from three sterile (singlet) neutrinos in the presence of a softly broken A₄ symmetry. We take the unconventional view that the sterile neutrinos may be light, i.e. less than 1 keV, and discuss some very interesting and novel phenomenology, including a connection between the LSND neutrino data and solar neutrino oscillations.