An infinite swampland of U(1) charge spectra in 6D supergravity theories

TL;DR

This paper investigates the landscape and swampland of 6D supergravity theories with U(1) gauge factors, revealing an infinite class of consistent theories not realizable via known string theory constructions, especially with larger charges or tensor multiplets.

Contribution

It identifies an infinite class of anomaly-free 6D supergravity theories with U(1) charges that cannot be realized through F-theory or other known string compactifications.

Findings

Models with charges ±1, ±2 match F-theory constructions

Infinite charge spectra exist in the swampland beyond known realizations

Comparison of abelian spectra with nonabelian symmetry breaking spectra

Abstract

We analyze the anomaly constraints on 6D supergravity theories with a single abelian U(1) gauge factor. For theories with charges restricted to $q = \pm1, \pm2$ and no tensor multiplets, anomaly-free models match those models that can be realized from F-theory compactifications almost perfectly. For theories with tensor multiplets or with larger charges, the F-theory constraints are less well understood. We show, however, that there is an infinite class of distinct massless charge spectra in the "swampland" of theories that satisfy all known quantum consistency conditions but do not admit a realization through F-theory or any other known approach to string compactification. We also compare the spectra of charged matter in abelian theories with those that can be realized from breaking nonabelian SU(2) and higher rank gauge symmetries.