6D SCFTs and the Classification of Homomorphisms $Γ_{ADE} \rightarrow E_8$
Darrin D. Frey, Tom Rudelius
TL;DR
This work establishes and tests a concrete correspondence between 6D SCFTs and homomorphisms $\Gamma\to E_8$, as predicted by string dualities. By leveraging refined global-symmetry analyses, it revisits the $\mathbb{Z}_k$ and $SL(2,5)$ cases, corrects misclassifications, and extends the classification to the dicyclic groups $\mathrm{Dic}_{k-2}$ and to $\Gamma_{E_{6,7}}$, showing that Dic$_{k-2}$ homomorphisms are labeled by D-partitions of $2k$ plus an admissible affinizing algebra. The RG-flow structure of these theories maps to a partial ordering on the homomorphisms, mirroring the nilpotent-orbit Hasse diagram, which provides a unifying picture of tensor/Higgs branch flows across the spectrum. The results bridge elliptic Calabi–Yau geometry, M-/F-theory constructions, and finite-group representation theory, and hint at deeper mathematical classifications tied to 6D SCFTs and their dimensional reductions.
Abstract
We elucidate the correspondence between a particular class of superconformal field theories in six dimensions and homomorphisms from discrete subgroups of $SU(2)$ into $E_8$, as predicted from string dualities. We show how this match works for homomorphisms from the binary icosahedral group $SL(2,5)$ into $E_8$, correcting previous errors in both the mathematics and physics literature. We use this correspondence to list the homomorphisms from binary dihedral groups, the binary tetrahedral group, and the binary octahedral group into $E_8$--a novel mathematical result. The partial ordering specified by renormalization group flows suggests an ordering on these homomorphisms similar to the known ordering of nilpotent orbits of a simple Lie algebra dictated by the Hasse diagram.
