Repercussions of the Peccei-Quinn axion on QCD

TL;DR

This paper investigates how the introduction of the Peccei-Quinn axion affects the nonperturbative features of QCD, challenging previous assumptions about their compatibility.

Contribution

It reveals that the axion extension conflicts with established low-energy QCD properties due to the integration of its anomalous gauge coupling.

Findings

Axion integration alters the QCD topological structure.

Conflict with low-energy QCD results identified.

Implications for axion phenomenology and QCD theory.

Abstract

The axion, originally postulated by Peccei and Quinn to solve the strong CP problem, has become of great interest in particle and astroparticle phenomenology. Yet it has a problem. It is widely assumed that the axion leaves the nonperturbative features of QCD unscathed. This is, however, not the case. On the contrary, the axion extension is found to be in conflict with seminal results on the low-energy properties of QCD. The key is that the anomalous coupling of the axion to the gauge bosons can be integrated out, leaving behind a path integral over topologically trivial gauge potentials.