LIGHT ADJOINT SCALARS AND UNIFICATION AT THE STRING SCALE

Following the suggestion of Bachas, Fabre and Yanagida (BFY), we analy ze the gauge coupling unification at the two-loop order, in a supersym metric scenario where scalars belonging to the adjoint representations contribute to the evolution of the couplings from intermediate scales onward, and the unification scale is pushed towards the string scale. Thereafter, we compare the masses of these adjoint scalars to the sca le at which the hidden sector gauge coupling reaches the nonperturbati ve limit at the two-loop order for various possible hidden sector gaug e groups motivated by the conjecture of BFY that the masses of these a djoint scalars are related to gaugino condensation. We also compute th e predictions for the top and bottom quark masses in this scenario and compare them with those of MSSM. The predicted bottom mass improves i n the BFY scenario for smaller values of alpha(s). (C) 1997 Published by Elsevier Science B.V.