Gaussian processes reconstruction of modified gravitational wave propagation

Recent work has shown that modified gravitational wave (GW) propagation can be a powerful probe of dark energy and modified gravity, specific to GW observations. We use the technique of Gaussian processes, which allows the reconstruction of a function from the data without assuming any parametrization, to measurements of the GW luminosity distance from simulated joint GW-gamma-ray-burst detections, combined with measurements of the electromagnetic luminosity distance by simulated data from the dark energy survey (DES). For the GW events, we consider both a second-generation LIGO/Virgo/Kagra (HVLKI) network, and a third-generation detector such as the Einstein Telescope. We find that the HVLKI network at target sensitivity, with $O(15)$ neutron star binaries with an electromagnetic counterpart, could already detect deviations from general relativity at a level predicted by some modified gravity models, and a third-generation detector such as the Einstein Telescope would have a remarkable discovery potential. We discuss the complementarity of the Gaussian processes technique to the $({\mathrm{\Xi }}_0,n)$ parametrization of modified GW propagation.