Energy conservation and axion back-reaction in a magnetic field

TL;DR

This paper develops a semi-analytic method to include axion back-reaction in the analysis of electromagnetic radiation emitted by axion clumps in magnetic fields, revealing how back-reaction influences clump resonance over time.

Contribution

It introduces a self-consistent approach that accounts for axion back-reaction via energy conservation, which was previously neglected in the study of axion-induced radiation.

Findings

Back-reaction alters the clump frequency evolution.

Clumps with various initial frequencies can become resonant.

The method provides a more complete understanding of axion decay dynamics.

Abstract

Axion clumps in an external magnetic field can emit electromagnetic radiation which causes them to decay. In the presence of a plasma, such radiation can become resonant if the clump frequency matches the plasma frequency. Typically, the decay or back-reaction of the clump is ignored in the literature when analyzing such radiation. In this paper we present a self consistent, semi-analytic approach which captures axion back-reaction using energy conservation. We find that inclusion of back-reaction changes the clump frequency over time enabling clumps with a range of different initial frequencies to become resonant at some point in their time evolution.