Neutrino Properties in a GUT Analysis for Fermion Masses

In practically all extentions of the standard model, the neutrinos naturally acquire a mass. The neutrino mass matrix, however, contains many parameters which can neither be predicted by the prevailing models nor can be fitted to the data. We propose a fermion mass matrix ansatz in the context of Grand Unified Supersymmetric Theories (GUTs) at the GUT scale and use the renormalization group equations for the gauge and Yukawa couplings to predict the 13 arbitrary parameters of the Standard model. The constraints imposed by the charged fermion data are used to make predictions in the neutrino sector. The neutrino mass matrix is worked out in the case of the flipped SU(5) model and the predictions are compared with the available experimental data.