Supersymmetry Enhancement and Junctions in S-folds

TL;DR

This paper investigates supersymmetry enhancement from ${ m extbf{N}=3}$ to ${ m extbf{N}=4}$ in S-fold theories using string junctions, revealing how non-perturbative effects reproduce central charges and comparing spectra with brane models.

Contribution

It provides a detailed analysis of supersymmetry enhancement via string junctions in S-folds, establishing a correspondence with perturbative brane spectra and deriving the enhanced central charge.

Findings

Confirmed the one-to-one correspondence between junction spectra and brane models.

Derived an explicit expression for the enhanced central charge $ar Z$.

Showed how non-perturbative effects reproduce the missing central charge.

Abstract

We study supersymmetry enhancement from ${\cal N}=3$ to ${\cal N}=4$ proposed by Aharony and Tachikawa by using string junctions in S-folds. The central charges carried by junctions play a central role in our analysis. We consider planer junctions in a specific plane. Before the S-folding they carry two complex central charges, which we denote by $Z$ and $\bar Z$. The S-fold projection eliminates $\bar Z$ as well as one of the four supercharges, and when the supersymmetry is enhanced $\bar Z$ should be reproduced by some non-perturbative mechanism. For the models of $\mathbb{Z}_3$ and $\mathbb{Z}_4$ S-folds which are expected to give $SU(3)$ and $SO(5)$ ${\cal N}=4$ theories we compare the junction spectra with those in perturbative brane realization of the same theories. We establish one-to-one correspondence so that $Z$ coincides. By using the correspondence we also give an expression for the enhanced central charge $\bar Z$.