Towards unification of GUT families

TL;DR

This paper explores a novel anti-SU(7) grand unification model derived from string theory, addressing the chiral matter problem, family unification, and natural doublet-triplet splitting, with promising phenomenological implications including CKM fit and proton decay predictions.

Contribution

It proposes an anti-SU(7) GUT model from Z(12-I) orbifold compactification that unifies families and naturally achieves doublet-triplet splitting.

Findings

The model fits CKM data.

Natural doublet-triplet splitting achieved.

Proton decay via GUT gauge bosons predicted.

Abstract

I discuss the mere 5 % of atoms in the cosmic energy pie. It is basically the chiral matter problem. Then, I review the chiral matter problem from a grand unification (GUT) point of view, and point out that anti-SU(N), easily implementable in string compactification, is a possibility. Here `anti-' means that the GUT group breaking is through the anti-symmetric tensor field(s), e.g. <\Phi^{[AB]}>= <\Phi_{[AB]}>. We argued for an anti-SU(7) [= SU(7) x U(1)] families-unification model from a Z(12-I) orbifold compactification. The Z(12-I) orbifold is briefly discussed and the multiplicity 2 in the T3 twisted sector is the key obtaining three chiral families. Yukawa coupling structure is shown to be promising. A numerical study shows that the anti-SU(7) model satisfies the CKM fit. It is shown that the doublet-triplet splitting is obtained naturally, where the dominant process for proton decay is by the exchange of GUT scale gauge bosons such that proton to pi-zero plus positron is the dominant channel.