T-branes and Yukawa Couplings

TL;DR

This paper investigates T-brane configurations in F-theory models, revealing that certain Yukawa couplings vanish for E7 breaking but are non-zero for E8, impacting proton decay predictions.

Contribution

It provides a detailed analysis of T-branes with Z3 and Z4 monodromies, showing their effects on Yukawa couplings in E7 and E8 gauge symmetry breaking scenarios.

Findings

Yukawa couplings vanish for E7 breaking.

Yukawa couplings are non-zero for E8 breaking.

Proton decay mediating terms are avoided in both cases.

Abstract

We consider various configurations of T-branes which are non-abelian bound states of branes and were recently introduced by Cecotti, Cordova, Heckman and Vafa. They are a refinement of the concept of monodromic branes featured in phenomenological F-theory models. We are particularly interested in the T-branes corresponding to Z3 and Z4 monodromies, which are used to break E7 or E8 gauge groups to SU(5) GUT. Our results imply that the up-type and down-type Yukawa couplings for the breaking of E7 are zero, whereas up-type and down-type Yukawa couplings, together with right handed neutrino Yukawas are non-zero for the case of the breaking of E8. The dimension four proton decay mediating term is avoided in models with either E7 or E8 breaking.