Cosmological Structure Formation and Soliton Phase Transition in Fuzzy Dark Matter with Axion Self-Interactions

TL;DR

This paper explores how attractive self-interactions in fuzzy dark matter, modeled as ultra-light axions, influence cosmic structure formation and induce a phase transition in soliton cores, with simulations showing enhanced small-scale structures and core transformations.

Contribution

It introduces the impact of axion-like self-interactions on fuzzy dark matter structure formation and reveals a phase transition in soliton cores through numerical simulations.

Findings

Self-interactions can enhance small-scale structure formation.

Soliton cores undergo a phase transition from dilute to dense states.

Simulations demonstrate the critical mass threshold for phase transition.

Abstract

We investigate cosmological structure formation in Fuzzy Dark Matter (FDM) with an attractive self-interaction (SI) with numerical simulations. Such a SI would arise if the FDM boson were an ultra-light axion, which has a strong CP symmetry-breaking scale (decay constant). Although weak, the attractive SI may be strong enough to counteract the quantum 'pressure' and alter structure formation. We find in our simulations that the SI can enhance small-scale structure formation, and soliton cores above a critical mass undergo a phase transition, transforming from dilute to dense solitons.