Proton Decay and Neutrino Masses in SO(10)

In the last few years physicists have been looking at $SO(10)$ GUT models with renewed attention because it has been realized that the SU(5) minimal model cannot unify the strong, electromagnetic and weak interactions in a way consistent with the experimental values of $\alpha(M_Z)$, $\si$ and $\alpha_S(M_Z)$. In this paper we derive lower limits on neutrino masses, relevant for cosmology and for the solar-neutrino problem, from necessary consistency conditions on a class of $SO(10)$ models with $\sq$ or $\stt$ intermediate gauge symmetry.