The recent detections and data releases from LIGO-Virgo enable the first applications of statistical methods for constraining the Hubble parameter with Gravitational Waves (GWs).
Moreover, they open up the possibility of new tests of General Relativity, since modified gravity models predict a non-standard GW luminosity distance, which is measured directly from the GW signal. By adding independent information on the redshift we can thus test this distance-redshift relation.
We present results with ''dark sirens'' (namely, compact binary coalescences without an electromagnetic counterpart) from the GWTC-2 catalogue, where the redshift information comes from the GLADE galaxy catalogue.
This leads to the most accurate measurement of $H_0$ and the first bounds on modified GW propagation from dark sirens alone.