Precursors from S(1)/Z2×Z2′ orbifold GUTs

Filipe Paccetti Correia,Michael Schmidt,Zurab Tavartkiladze

doi:10.1016/j.physletb.2003.06.037

Filipe Paccetti Correia, Michael Schmidt + Show 1 more

Open Access

https://doi.org/10.1016/j.physletb.2003.06.037

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Abstract

The possibility of appearance of GUT precursors near the TeV scale (suggested by Dienes–Dudas–Gherghetta) is addressed within 5D GUTs compactified on an S(1)/Z2×Z2′ orbifold. For a low compactification scale (large radius), there is a significant non universal logarithmic contribution in the relative running of gauge couplings. This within 5D SU(5), with the minimal field content, gives wrong prediction for α3(MZ) unless one goes beyond the minimal setting. The realization of the light precursors' idea thus requires some specific extensions. As a scenario alternative to SU(5) we also consider an SU(6) orbifold GUT, whose minimal non-SUSY version gives natural unification. In all the presented unification scenarios with light precursors, various GUT scales are realized. This allows the model to be naturally embedded in either heterotic or Type I string theories.

Highlights

One of the phenomenological motivations for SUSY GUTs is the successful unification of the gauge couplings near the scale MG ≃ 2 · 1016 GeV
In this paper we present a detailed study of the possibility of light precursors coming from 5D GUTs compactified on an S(1)/Z2 × Z2′ orbifold
We show that even if there is no power law relative running of gauge couplings, there is a non universal logarithmic contribution which for low μ0 becomes significantly large and does not allow unification with minimal field content

Summary

Introduction

One of the phenomenological motivations for SUSY GUTs is the successful unification of the gauge couplings near the scale MG ≃ 2 · 1016 GeV. In a recent paper [1] by Dienes, Dudas and Gherghetta the possibility of an orbifold construction was suggested where the compactification scale μ0 = 1/R (R is the radius of the compact extra dimension(s)) lies in the TeV range, while the GUT scale is still near 1016 GeV. As an alternative GUT model, we study the extended GUT gauge group SU(6) As it turns out, the non SUSY version of the 5D SU(6) GUT can naturally give unification with light precursors. If instead of SU (5) some extended gauge group is considered, compactification on an S(1)/Z2 × Z2′ orbifold still turns out to be an economical possibility for realistic model building.

SUSY case

Non-SUSY case

Discussions and conclusions