Gravitational Waves as a New Probe of Bose-Einstein Condensate Dark Matter

TL;DR

This paper proposes using gravitational wave speed deviations caused by Bose-Einstein condensate dark matter halos as a novel method to explore the properties of ultralight dark matter particles in the universe.

Contribution

It introduces a new observational technique leveraging gravitational wave speed changes to probe the parameter space of Bose-Einstein condensate dark matter models.

Findings

GW speed deviations depend on DM particle mass and self-interaction.

The method can effectively probe the entire BEC DM parameter space.

Future GW observations could significantly constrain BEC DM models.

Abstract

There exists a class of ultralight Dark Matter (DM) models which could form a Bose-Einstein condensate (BEC) in the early universe and behave as a single coherent wave instead of individual particles in galaxies. We show that a generic BEC DM halo intervening along the line of sight of a gravitational wave (GW) signal could induce an observable change in the speed of GW, with the effective refractive index depending only on the mass and self-interaction of the constituent DM particles and the GW frequency. Hence, we propose to use the deviation in the speed of GW as a new probe of the BEC DM parameter space. With a multi-messenger approach to GW astronomy and/or with extended sensitivity to lower GW frequencies, the entire BEC DM parameter space can be effectively probed by our new method in the near future.