HIGGS AND TOP MASS PREDICTIONS IN GUT MODELS WITH FIXED-POINT SOLUTIONS

We study fixed-point solutions in SU(5) and SO(10) super-symmetric gra nd unified models. For the SU(5) model with a single large h(t) coupli ng constant we find 155 GeV less than or equal to m(t) less than or eq ual to 200 GeV. For 155 GeV less than or equal to m(t) less than or eq ual to 175 GeV we find that the Higgs boson is lighter than M(Z). The SU(5) and SU(10) Fixed-point solutions with large h(t) and h(b) coupli ng constants give a top-quark mass m(h) = 180-190 GeV and a Higgs boso n mass m(h) = 118-120 GeV (for M(SUSY) = 1 TeV). From the requirement of the absence of a Landau pole singularity up to the Planck scale we find an upper bound on the top mass m(t) less than or equal to 209 GeV in the SU(5) model and m(t) less than or equal to 193 GeV for the SO( 10) model.