On Gauge Threshold Corrections for Local IIB/F-theory GUTs

TL;DR

This paper investigates gauge threshold corrections in local IIB/F-theory GUT models, revealing an enhancement of the unification scale due to bulk effects and hypercharge flux configurations, with implications for string theory model building.

Contribution

It demonstrates that the unification scale is increased from the string scale to R times the string scale due to hypercharge flux effects in local GUT models.

Findings

Unification scale is enhanced to R M_s due to hypercharge flux.

The enhancement is linked to uncancelled tadpoles sourcing closed string modes.

This mechanism applies broadly to models with globally trivial hypercharge flux.

Abstract

We study gauge threshold corrections for local GUT models in IIB/F-theory. Consistency with holomorphy requirements of supergravity and the Kaplunovsky-Louis formula implies that the unification scale is enhanced by the bulk radius R from the string scale to M_X =RM_S. We argue that the stringy interpretation of this is via a locally uncancelled tadpole sourced by the hypercharge flux. This sources closed string modes propagating into the bulk; equivalently open string gauge coupling running up to the winding scale M_X. The enhancement to R M_s is tied to GUT breaking by a globally trivial hypercharge flux and will occur in all models realising this mechanism.