Electromagnetic energy loss of axion stars

TL;DR

This paper investigates how axion stars interact with electromagnetic radiation in strong magnetic fields, revealing an asymptotic growth in their size over time through an analytic approach.

Contribution

It provides a fully analytic treatment of electromagnetic energy exchange in axion stars using variationally optimized profiles, offering new insights into their evolution.

Findings

Dilute axion stars exhibit a slow size increase over time.

Energy exchange rate can be described by a rate equation for axion number.

Asymptotic growth of axion star size follows a t^{1/5} pattern.

Abstract

The rate of energy exchange of spatially localized and gravitationally bound axion configurations with electromagnetic radiation is investigated in presence of strong static magnetic field. Fully analytic treatment is achieved based on variationally optimized separable spatio-temporal clump profiles. For dilute axion stars the equation of the energy variation is reinterpreted as a rate equation of the axion number. Its solutions hints to an asymptotic $\sim t^{1/5}$ increase of the clump size.