Scalar Dark Matter Clumps with Angular Momentum

TL;DR

This paper extends the analysis of light scalar dark matter clumps by including angular momentum, revealing how non-spherical configurations influence maximum mass and minimum radius, with implications for resonance phenomena.

Contribution

It introduces non-spherical, angular momentum-carrying configurations of scalar dark matter clumps, generalizing previous spherical models and correcting prior numerical inaccuracies.

Findings

Maximum mass increases with angular momentum in attractive interactions.

Minimum radius in repulsive interactions is larger for non-zero angular momentum.

Corrects previous claims of upper bounds on angular momentum due to numerical errors.

Abstract

The behavior of light scalar dark matter has been a subject of much interest recently as it can lead to interesting small scale behavior. In particular, this can lead to the formation of gravitationally bound clumps for these light scalars, including axions. In Ref. [1] we analyzed the behavior of these clumps, assuming spherical symmetry, allowing for both attractive and repulsive self-interactions. There is a maximum allowed mass for the clumps in the case of attractive interactions, and a minimum radius for the clumps in the case of repulsive interactions, which is saturated at large mass. Here we extend this work to include non-spherically symmetric clumps. Since the system tries to re-organize into a BEC ground state, we consider configurations with a conserved non-zero angular momentum, and construct minimum energy configurations at fixed particle number and fixed angular momentum. We find generalizations of the previous spherically symmetric results. In particular, while there is still a maximum mass for the attractive case, its value increases with angular momentum. Also, the minimum radius in the repulsive case is raised to higher radii. We clarify how a recent claim in the literature of an upper bound on angular momentum is due to inaccurate numerics. In a forthcoming paper we shall investigate the possibility of resonance of axion clumps into both visible and hidden sector photons, and analyze how the altered mass and radius from non-zero angular momentum affects the resonance.