In this talk, we introduce a new scenario of grand unified theory (GUT) with anomalous U(1)A gauge symmetry. Since generic interactions (including non-renormalizable interactions) are introduced, once we fix the symmetry of the theory, we can define the theory without O(1) coefficients. The number of parameters to determine the symmetry is just 11 or 12 integer parameters which are anomalous U(...

Requiring that supersymmetric SU(5) and SU(6) grand unifications in the heterotic string theory must have 3 chiral families, adjoint (or higher representation) Higgs fields in the grand unified gauge group, and a non-abelian hidden sector, we construct such string models within the framework of conformal field theory and asymmetric orbifolds. Within this framework, we construct all such string ...

We describe a supersymmetric Grand Unified Theory based on the gauge group SU(5), or SO(10), invariant under the interchange of any SU(5), or SO(10), with each family multiplet transforming non trivially under one different individual group factor. A realistic pattern of fermion masses and mixings is obtained as a result of an appropriate choice out of the many possible discretely degenerate va...