Neutrino masses and mixing angles in a predictive theory of fermion masses

A framework for predicting charged fermion masses in supersymmetric grand unified theories is extended to make predictions in the neutrino sector. Eight new predictions are made: the two neutrino mass ratios and the three mixing angles and three phases of the weak leptonic mixing matrix. There are three versions of the theory which are relevant for producing MSW neutrino oscillations in the Sun. One of these is preferred by the combined solar neutrino observations. Another will be probed significantly by the searches for ${\nu }_{\mu }{\mu }_{\tau }$ oscillations at the NOMAD, CHORUS, and P803 experiments. In this second version ${\nu }_{\tau }$ could be a significant component of the dark matter in the Universe.