Neutrino mass matrix suppression by Abelian charges with see-saw   mechanism
  We have investigated a neutrino mass matrix model without supersymmetry including three see-saw right-handed neutrinos around order $10^{12}$ GeV masses, aiming at a picture with all small numbers explained as being due to approximately conserved gauge charges. The prediction of the solar neutrino mixing angle is given by $\sin^22\theta_{\odot}= 3 {+3\atop -2}\times10^{-2}$; in fact, the solar mixing angle is, apart from detailed order unity corrections, equal to the Cabibbo angle. Furthermore the ratio of the solar neutrino mass square difference to that for the atmospheric neutrino oscillation is predicted to $6 {+11\atop -4}\times10^{-4}$ and is given by the same Cabibbo angle related parameter $\xi$ as $6 \xi^4$. 
H.B.Nielsen, Y.Takanishi