Gauge-Higgs Unification from the Heterotic String

TL;DR

This paper constructs a 6D orbifold heterotic string model with gauge-Higgs unification, anomaly cancellation, and realistic fermion generations, advancing string-based approaches to the standard model.

Contribution

It introduces a novel 6D orbifold heterotic string model with specific gauge symmetry breaking and matter localization, enabling gauge-Higgs unification and realistic Yukawa couplings.

Findings

Model achieves anomaly cancellation via Green-Schwarz mechanism.

Includes three fermion generations with realistic mass relations.

Supports vacua with partial or full gauge-Higgs unification.

Abstract

We present a 6D orbifold model on $T^2/\Z2$ which emerges as intermediate step in the compactification of the heterotic string to the supersymmetric standard model in four dimensions. It has $\SU6$ gauge symmetry in the bulk and two pairs of inequivalent fixed points with unbroken $\SU5$ and $\SU2 \times \SU4$ symmetry, respectively. All anomalies are cancelled by the Green-Schwarz mechanism. Two quark-lepton generations are located at the $\SU5$ branes, the third family is composed of split bulk hypermultiplets. The model has vacua with partial or full gauge-Higgs unification and non-vanishing Yukawa couplings which generically avoid the unsuccessful $\SU5$ mass relations.