Axions and Atomic Clocks

TL;DR

This paper explores how axion dark matter could influence electromagnetic wave propagation and atomic clock stability, proposing experimental methods to detect such effects and constrain axion properties.

Contribution

It introduces a novel approach to detect axion dark matter through modifications in electromagnetic dispersion relations affecting atomic clocks and interferometry.

Findings

Atomic clocks' frequency stability can potentially reveal axion backgrounds for $f_a \,\ge\, 10^7$ GeV.

Applying magnetic fields may enhance axion detection sensitivity.

Interferometric methods could probe time-varying photon dispersion caused by axions.

Abstract

The equations of electrodynamics are altered in the presence of a classical coherent axion dark matter background field, changing the dispersion relation for electromagnetic waves. Careful measurements of the frequency stability in sensitive atomic clocks could in principle provide evidence for such a background for $f_a \ge 10^7$ GeV. Turning on a background magnetic field might enhance these effects in a controllable way, and interferometric measurements might also be useful for probing the time-varying photon dispersion relation that results from a coherent cosmic axion background.