Probing the cosmic opacity from future gravitational wave standard sirens

In this work, using the Gaussian process, we explore the potentiality of future gravitational wave (GW) measurement to probe cosmic opacity through comparing its opacity-free luminosity distance (LD) with the opacity-dependent one from type Ia supernovae (SNIa). GW data points are simulated from the third-generation Einstein Telescope, and SNIa data are taken from the Joint Light Analysis (JLA) or Pantheon compilation. The advantages of using the Gaussian process are that one may match SNIa data with GW data at the same redshift and use all available data to probe cosmic opacity. We obtain that the error bar of the constraint on cosmic opacity can be reduced to σ_ɛ∼0.011 and 0.006 at 1 σ confidence level (CL) for JLA and Pantheon, respectively, in a cosmological-independent way. Thus, the future GW measurements can give competitive results on the cosmic opacity test. Furthermore, we propose a method to probe the spatial homogeneity of the cosmic transparency through comparing the reconstructed LD from the mock GW with the reconstructed one from SNIa data in a flat Λ CDM with the Gaussian process. The result shows that a transparent universe is favored at 1 σ CL, although the best-fit value of cosmic opacity is redshift dependent.