Supersymmetric trinification and low energy consequences

We describe a number of distinct approaches to supersymmetric trinification, a grand unification scheme in which SU(3)c x SU(3)L x SU(3)R is supplemented by a discrete symmetry to ensure unification of the three gauge couplings above MG(∼ 1016GeV). The first one employs the minimum number (two) of Higgs supermultiplets and leads to a 'non-minimal' low energy spectrum. Dimension five proton decay is absent and this is intimately related to the resolution of the gauge hierarchy problem. The second approach utilizes and additional Higgs supermultiplet, leads precisely to the minimal supersymmetric standard model (MSSM) at low energies, and provides a resolution of the gauge hierarchy problem through a pseudogoldstone mechanism. Dimension five proton decay is expected in this case to proceed at a rate somewhat below the SU(5) value. The third and final scenario is closely related in its predictions to the first one except that it yields MSSM at low energies by utilizing an additional Higgs superfield. The well known parameter tanβ of MSSM is predicted to be of order mt/mb in the first (and third) case with a stable proton, while it is of order unity in the second approach. (author)