Axion Electrodynamics and the Axionic Casimir Effect

TL;DR

This paper develops a framework for axion electrodynamics in media and explores the resulting electromagnetic effects, including axion-induced currents and mode splitting, with potential implications for astrophysics and laboratory experiments.

Contribution

It introduces a general scheme for axion electrodynamics in media and analyzes the resulting electromagnetic phenomena, including mode splitting and pressure effects, with numerical estimates.

Findings

Electromagnetic current density from axions in magnetic fields

Axion-induced mode splitting between metal plates

Quantitative estimates of pressure differences due to axions

Abstract

A general scheme for axion electrodynamics is given, in which a surrounding medium of constant permittivity and permeability is assumed. Then, as an application we give simple numerical estimates for the electromagnetic current density produced by the electrically neutral time-dependent axions $a=a(t)$ in a strong magnetic field. As is known, the assumption $a=a(t)$ is common under astrophysical conditions. In the third part of the paper, we consider the implications by assuming instead an axion amplitude $a(z)$ depending on one coordinate $z$ only. If such an axion field is contained within two large metal plates one obtains an axion-generated splitting of the eigenmodes for the dispersion relation. These modes yield equal, though opposite, contributions to the pressure on the plates. We calculate the magnitude of the splitting effect, in a simple one-dimensional model.