Orbifold Grand Unification: A Solution to the Doublet-Triplet Problem

TL;DR

This paper introduces a four-dimensional orbifold grand unified theory that addresses the doublet-triplet splitting problem in SU(5) models, naturally removing unwanted triplet components and achieving gauge coupling unification.

Contribution

It proposes a novel orbifold approach in 4D to break SU(5) symmetry and solve the doublet-triplet splitting problem without requiring an adjoint Higgs.

Findings

Successfully removes triplet Higgs components

Achieves gauge coupling unification in MSSM

Provides possible UV completions

Abstract

To solve the doublet-triplet splitting problem in SU(5) grand unified theories, we propose a four dimensional orbifold grand unified theory by acting Z2 on the SU(5) gauge group. Without an adjoint Higgs, the orbifold procedure breaks the SU(5) gauge symmetry down to the standard model gauge group, and removes the triplet component of the fundamental SU(5) Higgs. In the supersymmetric framework, we show that the orbifold procedure removes two triplet superfields of the Higgs multiplets and leaves us with the minimal supersymmetric standard model, which also solves the hierarchy problem and realizes gauge coupling unification. We also discuss possible UV completions of the orbifold theories.