Non-Abelian gauge symmetry of generations in the approach using a four-dimensional superstring with free fermions

The Grand Unification Theory with the (SU5 circle-times U1)circle-times(SU3 circle-times U1)H gauge group, in which (SU3 circle-times U1)H is the horizontal symmetry of quark-lepton generations, is considered within the framework of the approach using a four-dimensional superstring with free fermions. The horizontal hypercharge YH is used to quantize electromagnetic charges of quarks and leptons within the framework of standard SO10 16-plets. In the authors approach, construction of the horizontal gauge symmetry leads to the appearance of a new massive SO10 16-plet, which is a singlet with respect to the horizontal group. The resulting Higgs sector may enable the hidden gauge group to be suppressed significantly and to break the flip SU5 circle-times U1 symmetry first to SM and then to SUc3 circle-times Uem1. The Qem construction allows the authors to avoid states with exotic charges (Qexem = 1/nQem), whose emergence is characteristic of the approach using four-dimensional superstrings. In the authors approach, the horizontal group can be violated in the low-energy limit, which offers a possibility for the existence of a superweaklike mechanism of CP violation in the gauge sector of the SU3H group. 19 refs., 2 tabs