REDUCTION OF COUPLINGS AND FINITENESS IN REALISTIC SUPERSYMMETRIC GUTS

Reduction of couplings in supersymmetric GUTs is achieved by searching for renormalization group invariant (RGI) relations among couplings w hich hold beyond the unification scale. Finiteness is due to the fact that there exist RGI relations among couplings that guarantee the vani shing of the beta-functions of a N = 1 supersymmetric GUT even to all orders in perturbation theory. Of particular interest are the relation s among gauge and Yukawa couplings which lead to very interesting pred ictions of the top quark mass.