Axion dark matter and the Lattice

TL;DR

This paper reviews the axion as a dark matter candidate, focusing on the dynamics of axionic string-wall networks and the impact of high-temperature QCD susceptibility on predicting axion mass.

Contribution

It advances understanding of axion production from string-wall networks and assesses the sensitivity of predictions to high-temperature QCD parameters.

Findings

Progress in modeling axionic string-wall network dynamics.

Identification of key temperature ranges affecting axion mass predictions.

Analysis of the impact of QCD topological susceptibility on axion abundance.

Abstract

First I will review the QCD theta problem and the Peccei-Quinn solution, with its new particle, the axion. I will review the possibility of the axion as dark matter. If PQ symmetry was restored at some point in the hot early Universe, it should be possible to make a definite prediction for the axion mass if it constitutes the Dark Matter. I will describe progress on one issue needed to make this prediction -- the dynamics of axionic string-wall networks and how they produce axions. Then I will discuss the sensitivity of the calculation to the high temperature QCD topological susceptibility. My emphasis is on what temperature range is important, and what level of precision is needed.