Particle-Soliton Degeneracy in 2D Quantum Chromodynamics

TL;DR

This paper investigates the spectrum of 2D quantum chromodynamics with a fusion category symmetry, revealing degeneracies and stable states of particles and solitons through anyon condensation and fusion category representation theory.

Contribution

It provides exact results on the spectrum, degeneracies, and multiplet structures of particles and solitons in 2D QCD with fusion category symmetry, using novel mathematical techniques.

Findings

Particles and solitons often share the same representation and mass.

Fusion category symmetry implies the existence of stable states.

Spectrum degeneracies are represented by quiver diagrams.

Abstract

Quantum chromodynamics in two spacetime dimensions admits a finite non-invertible symmetry described mathematically by a fusion category. This symmetry is spontaneously broken at long distances, leading to distinct vacua. When the theory has a mass gap, the spectrum is therefore characterized by particle excitations above a single vacuum and soliton sectors interpolating between vacua. We use anyon condensation and the representation theory of fusion categories to obtain exact results about this spectrum, exhibiting the allowed multiplets. Often, particles and solitons are in the same representation and therefore must have equal masses. Furthermore, the fusion category symmetry frequently implies the existence of certain stable states in the spectrum. The resulting degeneracies are encoded in quiver diagrams where nodes are vacua and arrows are excited states.