Towards a viable grand unified model with MG ∼ Mstring and MI ∼ 1012 GeV

We present a model based on the gauge group SU(2)L×SU(2)R×SU(4)C with gauge couplings that are found to be unified at a scale MG near the string unification scale. The model breaks to the minimal supersymmetric standard model at a scale MI ∼ 1012 GeV, which is instrumental in producing a neutrino in a mass range that can serve as hot dark matter and this scale can also solve the strong CP problem via the Peccei-Quinn (PQ) mechanism with an invisible harmless axion. We show how this model can accommodate low and high values of tan β and “exotic” representations that often occur in string derived models. We show that this model has lepton flavor violation which can lead to processes which are one or two orders of magnitude below the current experimental limits.