A self-consistent wave description of axion miniclusters and their survival in the galaxy

TL;DR

This paper develops a wave-based model for axion miniclusters using the Schrödinger-Poisson system and studies their survival in the galaxy through perturbation analysis and Monte Carlo simulations.

Contribution

It introduces a self-consistent wave description of axion miniclusters and analyzes their stability and evolution under galactic perturbations.

Findings

Weakly bound clusters are destroyed by perturbations.

Strongly bound clusters become more compact, resembling axion stars.

Survival probability depends critically on the density profile.

Abstract

We present a solution of the Schr\"odinger-Poisson system based on the WKB ansatz for the wave function. In this way we obtain a description of a gravitationally bound clump of axion dark matter by a superposition of energy eigenstates with random phases. It can be applied to any self-consistent pair of radial density distribution and phase space density $f(E)$ related by Eddington's formula. We adopt this as a model for axion miniclusters in our galaxy and use it to study the mass loss due to a star encounter by using standard perturbation theory methods known from quantum mechanics. Finally, we perform a Monte Carlo study to estimate the surviving fraction of axion miniclusters in the dark matter halo of our galaxy. We find that the reaction to perturbations and the survival probability depend crucially on the density profile. Weakly bound clusters are heated up and eventually destroyed, whereas more strongly bound systems get even more compact as a result of perturbations and are driven towards an axion star configuration.