Global aspects of $3$-form gauge theory: implications for axion-Yang-Mills systems

TL;DR

This paper explores the deep infrared behavior of axion-Yang-Mills systems, proposing a 3-form gauge theory framework that captures their global properties, symmetries, and anomalies, providing new insights into their vacuum structure and symmetry breaking.

Contribution

It develops a systematic framework for analyzing 3-form gauge theories coupled to axions, connecting them to infrared physics of axion-Yang-Mills systems with detailed symmetry and anomaly considerations.

Findings

3-form gauge theory describes vacua and domain walls in axion-Yang-Mills systems

The framework matches the infrared physics with the ultraviolet theory's anomalies

Emergence of a dynamical 3-form gauge field below the strong-coupling scale

Abstract

We investigate the proposition that axion-Yang-Mills systems are characterized by a $3$-form gauge theory in the deep infrared regime. This hypothesis is rigorously examined by initially developing a systematic framework for analyzing $3$-form gauge theory coupled to an axion, specifically focusing on its global properties. The theory consists of a BF term deformed by marginal and irrelevant operators and describes a network of vacua separated by domain walls converging at the junction of an axion string. It encompasses $0$- and $3$-form spontaneously broken global symmetries. Utilizing this framework, in conjunction with effective field theory techniques and 't Hooft anomaly-matching conditions, we argue that the $3$-form gauge theory faithfully captures the infrared physics of the axion-Yang-Mills system. The ultraviolet theory is an $SU(N)$ Yang-Mills theory endowed with a massless Dirac fermion coupled to a complex scalar and is characterized by chiral and genuine $\mathbb{Z}_m^{(1)}$ $1$-form center symmetries, with a mixed anomaly between them. It features two scales: the vev of the complex scalar, $v$, and the strong-coupling scale, $\Lambda$, with $\Lambda \ll v$. Below $v$, the fermion decouples and a $U(1)^{(2)}$ $2$-form winding symmetry emerge, while the $1$-form symmetry is enhanced to $\mathbb Z_N^{(1)}$. As we flow below $\Lambda$, matching the mixed anomaly necessitates introducing a dynamical $3$-form gauge field of $U(1)^{(2)}$, which appears as the incarnation of a long-range tail of the color field. The infrared theory possesses spontaneously broken chiral and emergent $3$-form global symmetries. It passes several checks, among which: it displays the expected restructuring in the hadronic sector upon transition between the vacua, and it is consistent under the gauging of the genuine $\mathbb Z_m^{(1)}\subset \mathbb Z_N^{(1)}$ symmetry.