$\mathcal{N} = 2$ Orbi-S-Folds

TL;DR

This paper constructs new non-compact Type IIB backgrounds combining S-folds and 7-branes, and studies the resulting 4D superconformal theories, linking them to 6D theories and cataloging rank-three examples to advance the classification of $ =2$ SCFTs.

Contribution

It introduces a novel class of backgrounds and establishes a correspondence with 6D theories, providing detailed data and a catalog of rank-three $ =2$ SCFTs for the first time.

Findings

Determined central charges and spectra of Coulomb-branch operators.

Mapped the setup to torus compactifications of 6D theories with Stiefel-Whitney twists.

Provided a comprehensive catalog of rank-three $ =2$ SCFTs.

Abstract

We introduce a new class of non-compact backgrounds of Type IIB string theory preserving eight supercharges by combining S-folds and non-perturbative 7-branes wrapping orbifolds, and study the four-dimensional superconformal field theories arising at low energy on $D3$-branes probing them. We draw a precise correspondence between this setup and the torus compactification of six-dimensional orbi-instanton theories with a Stiefel-Whitney twist, and use it to determine the main features of such strongly-coupled systems, like central charges, spectra of Coulomb-branch operators, networks of Higgs-branch flows. Finally, with the aim to improve our understanding of the landscape of $\mathcal{N}=2$ superconformal field theories, and possibly to extend their classification beyond rank two, we provide a detailed catalogue of all the rank-three theories that our framework gives access to.