Constraints on the cosmic distance duality relation with simulated data of gravitational waves from the Einstein Telescope.

The cosmic distance duality relation has been test through several astronomical observations in the last years. This relation establishes a simple equation relating the angular diameter ($D_A$) and luminosity ($D_L$) distances at a redshift $z$, $D_LD_A^{-1}(1+z)^{-2}=\eta=1$. However, only very recently this relation has been observationally tested at high redshifts ($z \approx 3.6$) by using luminosity distances from type Ia supernovae (SNe Ia) and gamma ray bursts (GRBs) plus angular diameter distances from strong gravitational lensing (SGL) observations. No significant deviation from the CDDR validity has been verified, although the results did not rule out $\eta \neq 1$ with high confidence level. In this work, we test the potentialities of future luminosity distances from gravitational waves (GWs) sources to impose limit on possible departures of the CDDR jointly with current SGL observations. The basic advantage of $D_L$ from GWs is being insensitive to non-conservation of the number of photons. By simulating 600, 900 and 1200 data of GWs using the Einstein Telescope (ET) as reference, we derive limits on $\eta(z)$ function and obtain that the results will be at least competitive with current limits from the SNe Ia $+$ GRBs $+$ SGLs analyses.