Grand unification models from SO(32) heterotic string

Abstract

Grand unification groups (GUTs) are constructed from SO(32) heterotic string via [Formula: see text] orbifold compactification. So far, most phenomenological studies from string compactification relied on [Formula: see text] heterotic string, and this invites the SO(32) heterotic string very useful for future phenomenological studies. Here, spontaneous symmetry breaking is achieved by Higgsing of the antisymmetric tensor representations of SU[Formula: see text]. The anti-SU[Formula: see text] presented in this paper is a completely different class from the flipped-SU[Formula: see text]’s from the spinor representations of SO[Formula: see text]. Here, we realize chiral representations: [Formula: see text] for a SU(9) GUT and [Formula: see text] for a SU(5)[Formula: see text] GUT. In particular, we confirm that the non-Abelian anomalies of SU(9) gauge group vanish and hence our compactification scheme achieves the key requirement. We also present the Yukawa couplings, in particular for the heaviest fermion, [Formula: see text], and lightest fermions, neutrinos. In the supersymmetric version, we present a scenario how supersymmetry can be broken dynamically via the confining gauge group SU(9). Three families in the visible sector are interpreted as the chiral spectra of SU[Formula: see text] GUT.