SU(5) orientifolds, Yukawa couplings, Stringy Instantons and Proton Decay

TL;DR

This paper constructs SU(5) orientifold models, analyzes superpotential couplings including Yukawa and baryon number violating terms, and investigates instanton effects that generate missing Yukawa couplings while assessing proton decay risks.

Contribution

It provides a systematic construction of SU(5) orientifold vacua and identifies instanton effects that generate crucial Yukawa couplings, addressing proton decay concerns.

Findings

Identified conditions for Yukawa couplings in SU(5) orientifold vacua

Found instanton effects that generate missing Yukawa couplings in some models

Highlighted the potential for rapid proton decay from certain superpotential terms

Abstract

We construct a large class of SU(5) orientifold vacua with tadpole cancellation both for the standard and the flipped case. We give a general analysis of superpotential couplings up to quartic order in orientifold vacua and identify the properties of needed Yukawa couplings as well as the baryon number violating couplings. We point out that successful generation of the perturbatively forbidden Yukawa couplings entails a generically disastrous rate for proton decay from an associated quartic term in the superpotential, generated from the same instanton effects. We search for the appropriate instanton effects that generate the missing Yukawa couplings in the SU(5) vacua we constructed and find them in a small subset of them.