Automatic Enhancement in 6D Supergravity and F-theory Models

TL;DR

This paper investigates automatic gauge group enhancements in 6D supergravity and F-theory models, revealing a principle that constrains possible theories and may eliminate many from the swampland.

Contribution

It proposes a universal principle explaining automatic gauge enhancements in F-theory models, impacting the classification of consistent 6D supergravity theories.

Findings

Automatic enhancements occur when a containing theory cannot be Higgsed down.

Many swampland models with U(1) and SU(N) gauge groups are potentially ruled out.

The principle applies broadly, including exotic matter and infinite charge families.

Abstract

We observe that in many F-theory models, tuning a specific gauge group $G$ and matter content $M$ under certain circumstances leads to an automatic enhancement to a larger gauge group $G' \supset G$ and matter content $M' \supset M$. We propose that this is true for any theory $G, M$ whenever there exists a containing theory $G', M'$ that cannot be Higgsed down to $G, M$. We give a number of examples including non-Higgsable gauge factors, nonabelian gauge factors, abelian gauge factors, and exotic matter. In each of these cases, tuning an F-theory model with the desired features produces either an enhancement or an inconsistency, often when the associated anomaly coefficient becomes too large. This principle applies to a variety of models in the apparent 6D supergravity swampland, including some of the simplest cases with U(1) and SU(N) gauge groups and generic matter, as well as infinite families of U(1) models with higher charges presented in the prior literature, potentially ruling out all these apparent swampland theories.