Future prospects on testing extensions to $\Lambda$CDM through the weak lensing of gravitational waves

Understand

With planned space-based and 3rd generation ground-based gravitational wave detectors (LISA, Einstein Telescope, Cosmic Explorer), and proposed DeciHz detectors (DECIGO, Big Bang Observer), it is timely to explore statistical cosmological tests that can be employed with the forthcoming plethora of data, $10^4-10^6$ mergers a year.

• We forecast the combination of the standard siren measurement with the weak lensing of gravitational waves from binary mergers.
• For 10 years of 3rd generation detector runtime, this joint analysis will constrain the dark energy equation of state with marginalised $1\sigma$ uncertainties of $\sigma(w_0)$~0.005 and $\sigma(w_a)$~0.04.
• This is comparable to or better than forecasts for future galaxy/intensity mapping surveys, and better constraints are possible when combining these and other future probes with gravitational waves.