Model—Independent Probe of Cosmic Distance Duality Relation

Abstract In this paper, cosmic distance duality relation (CDDR) is probed without considering any background cosmological model. The only a priori assumption is that the Universe is described by the Friedmann–Lemaître–Robertson–Walker (FLRW) metric. The strong gravitational lensing data is used to construct the dimensionless co-moving distance function d ( z ) and latest type Ia supernovae Pantheon+ data is used to estimate luminosity distances at the corresponding redshifts z . Using the distance sum rule along null geodesics of the FLRW metric, the CDDR violation is probed in both flat and non-flat spacetime by considering two parametrizations for η ( z ), the function generally used to probe the possible deviations from CDDR. The results show that CDDR is compatible with the observations at a very high level of confidence for linear parametrization in a flat Universe. In a non-flat Universe too, CDDR is valid within the 1 σ confidence interval with a mild dependence of η on the curvature density parameter Ω K . The results for nonlinear parametrization also show no significant deviation from CDDR.