Superfluid dark matter flow around cosmic strings

TL;DR

This paper investigates how cosmic strings influence superfluid dark matter distribution, revealing conditions for BEC formation and providing an upper mass bound for dark matter particles based on wake thermalization.

Contribution

It analyzes the interaction between cosmic strings and superfluid dark matter, deriving bounds on dark matter particle mass and conditions for Bose-Einstein condensate formation.

Findings

A weak shock is induced in SFDM when a string passes through a condensed region.

A wake of increased density forms behind the string, potentially allowing BEC formation.

An upper mass bound of about 10 eV for dark matter particles is derived from wake thermalization conditions.

Abstract

We consider a cosmic string moving through a gas of superfluid dark matter (SFDM) particles and analyze how it affects the dark matter distribution. We look at two different cases: first, a cosmic string passing through an already condensed region, and second, through a region that is not yet condensed. In the former, the string induces a weak shock in the superfluid, and the Bose-Einstein condensate (BEC) survives. In the latter, a wake of larger density is formed behind the string, and we study under which conditions a BEC can be formed in the virialized region of the wake. By requiring the thermalization of the DM particles and the overlap of their de Broglie wavelengths inside the wake, we obtain an upper bound on the mass of the dark matter particles on the order of 10 eV, which is compatible with typical SFDM models.