White dwarfs as a probe of exceptionally light QCD axions

TL;DR

This paper investigates how extremely light QCD axions influence white dwarf structures, revealing that their effects on nucleon mass and stellar composition can help explore new axion parameter spaces beyond dark matter considerations.

Contribution

It introduces a novel method to probe light QCD axions through white dwarf observations, independent of dark matter assumptions.

Findings

Axions cause a significant reduction in nucleon mass at finite density.

White dwarf mass-radius relations are notably altered by axion effects.

The study opens new parameter space for axion detection via stellar observations.

Abstract

We study the effects of exceptionally light QCD axions on the stellar configuration of white dwarfs. At finite baryon density, the non-derivative coupling of the axion to nucleons displaces the axion from its in-vacuum minimum which implies a reduction of the nucleon mass. This dramatically alters the composition of stellar remnants. In particular, the modifications of the mass-radius relationship of white dwarfs allow us to probe large regions of unexplored parameter space without requiring that axions are dark matter.