Tumbling for Exotic Fermionic Representations in Grand Unified Models

Abstract

We consider dynamical symmetry breaking through a tumbling mechanism for exotic representations of fermions in unified models. Possible ways to introduce U(I) gauge symmetry are also discussed. It is shown that the most attractive channel (MAC) hypothesis does not predict physically interesting results unless the peculiar assumption of the maximal preservation of the global SU(3)xU(l) symmetry is made. In such a case the model with two fermionic generations is obtained.