Numerical simulations of Scalar Dark Matter Around Binary Neutron Star mergers

TL;DR

This study uses numerical simulations to explore how light scalar dark matter interacts with binary neutron star mergers, revealing potential observable effects that are generally too subtle for current detectors.

Contribution

It demonstrates that scalar dark matter can form a bound cloud around merging neutron stars, affecting their gravitational-wave signals in ways that are mostly undetectable with existing technology.

Findings

Scalar field forms a stable cloud around the binary

High-density scalar clouds cause measurable dephasing

Effects are small at astrophysically motivated densities

Abstract

Binary neutron star mergers provide a laboratory for probing fundamental physics through their gravitational-wave emission and electromagnetic counterparts. In particular, they may allow us to explore signatures of physics beyond the Standard Model in strong-gravity regimes, such as those of dark matter. In this work, we investigate the dynamics of light dark matter, modeled as a minimally coupled scalar field, surrounding a binary neutron star system. Our primary focus is to assess whether the scalar field remains bound to the binary over the late inspiral-merger timescales and to determine its potential impact on observable signatures. We find that, in a range of scenarios, the scalar field forms a common cloud around the binary that does not disperse. At sufficiently high densities, this leads to measurable effects, including a dephasing of the binary inspiral, a less compact post-merger remnant, and suppression of the dynamical ejecta. For densities motivated by astrophysical considerations, however, these effects remain small and are unlikely to be detectable with current or next-generation gravitational-wave observatories.