Gravitational wave lensing: probing Fuzzy Dark Matter with LISA

TL;DR

This paper investigates how gravitational wave lensing by Fuzzy Dark Matter halos, especially solitonic cores, can produce detectable wave optics signatures in LISA observations, helping distinguish FDM from cold dark matter.

Contribution

It demonstrates that wave optics effects in GW signals can reveal FDM halo properties and differentiate them from cold dark matter in LISA data.

Findings

Diffraction signatures vary with FDM halo mass.

FDM and CDM profiles can be distinguished via GW signals.

Dense solitonic cores do not significantly improve detection at large offsets.

Abstract

Gravitational lensing is a universal phenomenon: it affects both gravitational waves (GWs) and electromagnetic signals travelling through the gravitational field of a massive object. In this work, we explore the prospects of observing lensed GW signals from the mergers of massive black holes, lensed by dark matter halos composed of Fuzzy Dark Matter (FDM), which form dense cores known as solitons. We focus on wave optics phenomena, where frequency-dependent signatures can be observed in the weak lensing regime (i.e. single-image). Our results show that lensing diffraction signatures differ for low-mass halos in FDM, and can reveal the presence of a solitonic core. Furthermore, we demonstrate that FDM and cold dark matter profiles can be distinguished in GW signals from binary massive black hole mergers, which will be observed by the Laser Interferometer Space Antenna (LISA) mission. However, the dense solitonic core does not substantially enhance the detectability of FDM halos at large source-lens offsets, relative to standard cold dark matter. Our analysis confirms FDM halos as a promising signature of dark matter on GW observations.