More Axion Stars from Strings

TL;DR

This paper demonstrates that a significant fraction of post-inflationary QCD axion dark matter can form Bose stars early in the universe, which may persist and influence current phenomenology and detection efforts.

Contribution

It shows that over ten percent of axion dark matter efficiently collapses into Bose stars, a result largely independent of axion mass uncertainties.

Findings

Over ten percent of axion dark matter forms Bose stars.

Bose stars have asteroid masses and Earth-Moon scale sizes.

Potential implications for dark matter phenomenology and experiments.

Abstract

We show that if dark matter consists of QCD axions in the post-inflationary scenario more than ten percent of it efficiently collapses into Bose stars at matter-radiation equality. Such a result is mostly independent of the present uncertainties on the axion mass. This large population of solitons, with asteroid masses and Earth-Moon distance sizes, might plausibly survive until today, with potentially interesting implications for phenomenology and experimental searches.