Diffractive Lensing of Gravitational Waves as a New Probe of Dark Matter

Lensed gravitational waves (GWs) offer a promising new probe of dark matter. Dark matter subhalos can lens GWs from stellar-mass or massive black hole binaries, producing diffractive (wave-optics) lensing signatures in their chirping waveforms.

I will begin by highlighting how GW lensing differs from the lensing of light, particularly in its sensitivity to small-scale structure through frequency-dependent diffraction patterns. I will then discuss how these diffractive features encode the mass and density profile of dark matter subhalos, and how the rate of such events can inform their abundance. I will assess the detection prospects for current and upcoming GW detectors, and conclude by outlining key theoretical and computational challenges that must be addressed to advance this emerging probe.