Supersymmetric Indices of 3d S-fold SCFTs

TL;DR

The paper addresses how infrared symmetry and supersymmetry can enhance in 3d S-fold SCFTs by exploiting the 3d supersymmetric index. It employs a systematic index-based analysis of small-rank quiver theories built from $T(U(N))$ blocks and duality-wall constructions to diagnose SUSY enhancement, dualities, and the impact of gauge-group global structure (e.g., $SU(2)$ vs $SU(2)/Z_2$). Key findings include multiple examples where the index signals enhancement from ${ m N}=3$ to ${ m N}=4$ (and in some cases to ${ m N}=5$) and the identification of operator maps across dual quivers, as well as new phenomena tied to discrete topological symmetries and monopole operators. Overall, the work demonstrates the index as a powerful, calculable probe of IR symmetry and dualities in 3d $S$-fold SCFTs with varied matter content and global structure, and suggests directions for uncovering new interacting SCFTs and broader dualities.

Abstract

Enhancement of global symmetry and supersymmetry in the infrared is one of the most intriguing phenomena in quantum field theory. We investigate such phenomena in a large class of three dimensional superconformal field theories, known as the S-fold SCFTs. Supersymmetric indices are computed for a number of theories containing small rank gauge groups. It is found that indices of several models exhibit enhancement of supersymmetry at the superconformal fixed point in the infrared. Dualities between S-fold theories that have different quiver descriptions are also analysed. We explore a new class of theories with a discrete global symmetry, whose gauge symmetry in the quiver has a different global structure from those that have been studied earlier.