In the framework of four dimensional heterotic superstring with free fermions we investigate the rank eight Grand Unified String Theories (GUST) which contain the SU(3)H-gauge family symmetry. We explicitly construct GUSTs with gauge symmetry G = SU(5) × U(1) × (SU(3) × U(1))H ⊂ SO(16) ⊂ E(8) in free complex fermion formulation. We solve the problem of the GUST symmetry breaking taking for the observable gauge symmetry the diagonal subgroup Gsym of rank 16 group G × G ⊂ SO(16) × SO(16) ⊂ E(8) × E(8). In this approach the observed electromagnetic charge Qem can be viewed as a sum of two Q1- and Q2-charges of each G-group. In this case the model spectrum does not contain particles with exotic fractional charges.
|Number of pages||10|
|Journal||Physics Letters. Section B: Nuclear, Elementary Particle and High-Energy Physics|
|Publication status||Published - 2 Jun 1994|