DGRAV Minus DAP: Gravitational-wave cosmology without astrophysics
Gravitational wave signals from merging compact objects can be used to measure the expansion history of the Universe, offering a direct and elegant probe of cosmological parameters such as the Hubble constant, the curvature of the Universe, and dark energy equation of state. In this talk, we describe the ways in which gravitational wave sources detected by LIGO and Virgo are used to make this measurement, with varying levels of information from electromagnetic counterparts. We will present recent work on the spectrum of compact object masses obtained via gravitational wave detections and explain how it can be used to measure the expansion history of the universe. This method, dubbed "spectral siren cosmology," has been commonly presumed to require a theoretical prediction for the shape of the compact object mass spectrum. This would pose a serious limitation to the method since such predictions involve detailed knowledge of several complex and uncertain astrophysical processes. However, we will show that spectral sirens can be used to obtain accurate measurements of cosmological parameters while remaining agnostic to astrophysics.