The Aligned SU(5) xU(1)2 Model

In Calabi-Yau string compactification, it is pointed out that there exists anew type of $SU(5) \times U(1)^2$ model (the aligned $SU(5) \times U(1)^2$model) in which the $SU(5)$ differs from the standard $SU(5)$ and also from theflipped $SU(5)$. With the aid of the discrete symmetry suggested from Gepnermodel, we construct a simple and phenomenologically interestingthree-generation model with the aligned $SU(5) \times U(1)^2$ gauge symmetry.The triplet-doublet splitting problem can be solved. It is also found thatthere is a realistic solution for solar neutrino problem and for the $\mu$-problem. At low energies this model is in accord with the minimalsupersymmetric standard model except for the existence of singlet fields withmasses of $O(1)$TeV.Comment: LaTeX 24 page