How do you measure the universe's expansion with silent black holes?

Measuring the Hubble constant using gravitational-wave events whose host galaxies aren't identified requires integrating over huge volumes of sky for every event — a computation that becomes crushing as catalogs grow. By rewriting the gwcosmo pipeline to run on GPUs, the team cut analysis time from months to hours, handling the hundreds of events expected from LIGO's fifth observing run. That leap makes population-level cosmology from 'dark sirens' genuinely practical at scale.