A note on dimension-5 operators in GUTs and their impact

TL;DR

This paper analyzes how dimension-5 operators from quantum gravity or string theory affect gauge unification in GUTs, focusing on group-theoretic aspects and implications for model building and gaugino mass non-universality.

Contribution

It provides a comprehensive group-theoretic analysis of dimension-5 operators in SU(5), SO(10), and E(6) GUTs, identifying specific Higgs representations that enable unification consistent with experimental constraints.

Findings

Only a 200-dimensional Higgs in SU(5) can achieve unification below the Planck scale.

In supersymmetric models, 24, 75, or 200 Higgs representations are all compatible.

Results inform non-universality of gaugino masses in certain SUSY models.

Abstract

Quantum gravity or string compactification can lead to effective dimension-5 operators in Grand Unified Theories which modify the gauge kinetic terms. We exhaustively discuss the group-theoretic nature of such operators for the popular SU(5), SO(10), and E(6) models. In particular, for SU(5) only a Higgs in the 200 representation can help bring the couplings to unification below the Planck scale and in consistency with proton decay limits while for a supersymmetric version 24, 75, or 200 representations are all acceptable. The results also have a direct application in non-universality of gaugino masses in a class of supersymmetric models where identical group-theoretic features obtain.