Modified gravitational wave propagation: information from strongly lensed binaries and the BNS mass function

Abstract

Modified gravitational wave propagation is a smoking gun of modifications of gravity at cosmological scales, and can be the most promising observable for testing such theories. The observation of gravitational waves (GW) in recent years has allowed us to start probing this effect, and here we briefly review two promising ways of testing it. We will show that, already with the current network of detectors, it is possible to reach an interesting accuracy in the estimation of the Ξ0 parameter (that characterizes modified gravitational wave propagation, with Ξ0,GR = 1) and with next generation facilities, such as the Einstein Telescope, we can get a sub-percent measurement.

The clustering of dark sirens' invisible host galaxies

“…In this case, one must rely on statistical methods to extract source redshifts and study cosmology. Inferrence of the source redshift is informed by two pieces of information: firstly, a knowledge of features in the intrinsic (source-frame) mass distribution of black holes and neutron stars [6][7][8][9][10][11][12][13], when compared to the redshifted masses extracted from a waveform. Secondly, one can exploit a galaxy catalogue to provide the redshift distribution of observed galaxies, and hence a subset of the possible host galaxies of the event.…”