Speaker
Description
Strongly lensed gravitational waves offer a new way to study dark matter structure on subgalactic scales. In the wave-optics regime, gravitational waves propagating through a population of dark matter subhalos acquire frequency-dependent amplitude and phase distortions that encode the small-scale matter distribution along the line of sight.
We compute the full diffraction integral for gravitational waves propagating through statistically generated cold dark matter subhalo populations embedded in realistic galaxy-scale lenses, and evaluate the resulting signals in the Laser Interferometer Space Antenna (LISA) band. We find that strongly magnified images generically exhibit percent-level wave-optics modulations induced primarily by subhalos with masses in the range $10^4$–$10^7\, M_\odot$.
These signatures arise naturally within the standard cold dark matter paradigm and should be detectable in high–signal-to-noise strongly lensed LISA events. Strongly lensed gravitational waves therefore provide a direct and complementary probe of dark matter substructure at mass scales that are difficult to access with conventional electromagnetic lensing observations.