Discrete Gauging in Six Dimensions

TL;DR

This paper explores the effects of discrete gauging of symmetric groups in six-dimensional theories arising from coincident M5 branes on A-type singularities, revealing new phases and symmetry behaviors.

Contribution

It proposes that the $S_n$ flavor symmetry is gauged at the coincident point, providing a novel understanding of the phases and symmetry structures in M5 brane systems.

Findings

Discrete $S_n$ symmetry is gauged at coincident M5 branes.

Multiple Higgs and Coulomb branch phases are characterized.

Results extend to M5 branes near M9 planes.

Abstract

When $n$ M5 branes coincide on an A type singularity, $\mathbb{C}^2/\mathbb{Z}_k$, there is a multitude of tensionless strings which arise in the spectrum. The low energy theory when all M5 branes are separated at the singularity is given by a linear quiver with parameters $n$ and $k$. The theory has a multitude of phases, as many as partitions of $n$, each characterized by a different Higgs branch. Each such Higgs branch can be described by a Coulomb branch of a 3d $\mathcal{N}=4$ quiver. For example, at finite coupling, when all branes are separated, the quiver has a bouquet of $n$ $U(1)$ nodes connected to a single node. There is a natural discrete non Abelian $S_n$ global symmetry which acts in the theory by permuting $n$ identical objects. It acts in particular on the Higgs branch at the above finite coupling phase. It is conjectured that at the coincident point this discrete $S_n$ flavor symmetry is gauged, and at partial coincidence the corresponding subgroup of $S_n$ is gauged. This elegant and simple effect solves several problems which are raised recently on the physics of multiple M5 branes on an A type singularity. Similar results on multitude of phases are concluded for a system of $n$ M5 branes on an A type singularity next to an M9 plane.