### Abstract

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 G^{sym} of rank 16 group G × G ⊂ SO(16) × SO(16) ⊂ E(8) × E(8). In this approach the observed electromagnetic charge Q^{em} can be viewed as a sum of two Q^{1}- and Q^{2}-charges of each G-group. In this case the model spectrum does not contain particles with exotic fractional charges.

Original language | English |
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Pages (from-to) | 319-328 |

Number of pages | 10 |

Journal | Physics Letters. Section B: Nuclear, Elementary Particle and High-Energy Physics |

Volume | 328 |

Issue number | 3-4 |

DOIs | |

Publication status | Published - 2 Jun 1994 |

Externally published | Yes |

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## Cite this

*Physics Letters. Section B: Nuclear, Elementary Particle and High-Energy Physics*,

*328*(3-4), 319-328. https://doi.org/10.1016/0370-2693(94)91486-9