THE ALIGNED SU(5)X U(1)(2) MODEL

In Calabi-Yau string compactification, it is pointed out that there exists a new type of SU(5) x U(1)(2) model (the aligned SU(5)x U(1)2 model) in which the SU(5) differs from the standard SU(5) and also from the flipped SU(5). With the aid of the discrete symmetry suggested from Gepner model, we propose a simple and phenomenologically interesting three-generation model with the aligned SU(5) x U(1)(2) gauge symmetry. The triplet-doublet splitting problem can be solved. It is also found that there is a realistic solution for solar neutrino problem and for the mu-problem. At low energies this model is in accord with the minimal supersymmetric standard model except for the existence of singlet fields with masses of O(1)TeV.