Grand unfication models from SO(32) heterotic string

Grand unification groups (GUTs) are constructed from SO(32) heterotic string via Z(12-I) orbifold compactification. So far, most phenomenological studies from string compactification relied on E-8 x E-8 ' 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(N). The anti-SU(N) presented in this paper is a completely different class from the flipped-SU(N)'s from the spinor representations of SO(2N). Here, we realize chiral representations: (36) over bar over bar circle plus 5 . (9) over bar for a SU(9) GUT and 3{10(L)'circle plus (5) over barL '} for a SU(5)' 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, t, 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(5)' GUT.