# The QCD axion beyond the classical level: A lattice study

## TL;DR

This paper presents a pioneering lattice simulation of the QCD axion, challenging existing phenomenological models by providing a fully dynamical analysis of its mass.

## Contribution

It introduces the first fully dynamical lattice study of the Peccei-Quinn theory focusing on the axion mass, beyond semi-classical approximations.

## Key findings

- Simulation results conflict with current axion phenomenology.
- Provides new insights into the non-perturbative properties of the QCD axion.
- Challenges existing theoretical assumptions about axion mass predictions.

## Abstract

The axion is a hypothetical elementary particle postulated by the Peccei-Quinn theory to resolve the strong CP problem in QCD. If axions exist and have low mass, they are a candidate for dark matter as well. So far our knowledge of the properties of the QCD axion rests on semi-classical arguments and effective theory. In this work we perform, for the first time, a fully dynamical investigation of the Peccei-Quinn theory, focussing on the axion mass, by simulating the theory on the lattice. The results of the simulation are found to be in conflict with present axion phenomenology.