Enumerating 6D supergravities with $T\leq 1$

Abstract

The space of 6D supergravities with minimal supersymmetry is greatly constrained by anomaly cancellation. Nevertheless, a large number of models satisfy all low-energy consistency conditions and in this work we make progress towards exhaustively enumerating all anomaly-free models with at most one tensor multiplet. Generalizing previous techniques, we describe a general algorithm using multi-hypergraphs and simplicial complexes to systematically enumerate anomaly-free models with gauge groups of any number of simple factors and with hypermultiplets falling into any representations. Using these new ideas, we obtain a \emph{complete} list of anomaly-free models for $T\leq 1$, the only simplifying assumption being that the gauge group contains no $\operatorname{U}(1)$, $\operatorname{SU}(2)$, $\operatorname{SU}(3)$ or $\operatorname{Sp}(2)$ factors. We also study how many/which models in this ensemble satisfy several UV and swampland bounds which have been proposed and previously utilized to great effect, finding that none are ruled out for $T=0$ and $\approx\!50\%$ are inconsistent with quantum gravity for $T=1$.