PREPRINT
CEC044AB-52C7-4FD8-8D15-02A5C6179FE6

Condensation and Evaporation of Boson Stars

James Hung-Hsu Chan, Sergey Sibiryakov, Wei Xue
arXiv:2207.04057

Submitted on 8 July 2022

Abstract

Axion-like particles, including the QCD axion, are well-motivated dark matter candidates. Numerical simulations have revealed coherent soliton configurations, also known as boson stars, in the centers of axion halos. We study evolution of axion solitons immersed into a gas of axion waves with Maxwellian velocity distribution. Combining analytical approach with controlled numerical simulations we find that heavy solitons grow by condensation of axions from the gas, while light solitons evaporate. We deduce the parametric dependence of the soliton growth/evaporation rate and show that it is proportional to the rate of the kinetic relaxation in the gas. The proportionality coefficient is controlled by the product of the soliton radius and the typical gas momentum or, equivalently, the ratio of the gas and soliton virial temperatures. We discuss the asymptotics of the rate when this parameter is large or small.

Preprint

Comment: 44 pages, 18 figures

Subjects: Astrophysics - Cosmology and Nongalactic Astrophysics; High Energy Physics - Phenomenology; High Energy Physics - Theory

URL: https://arxiv.org/abs/2207.04057