What are recent observations telling us in light of improved tests of distance duality relation?

As an exact result required by the Etherington reciprocity theorem, the cosmic distance duality relation (CDDR), eta(z) = DL(z)(1 + z)-2/D A(z) =1 plays an essential part in modern cosmology. In this paper, we present a new method (eta(zi)/eta(zj)) to use the measurements of ultra-compact structure in radio quasars (QSO) and the latest observations of type Ia supernova (SN Ia) to test CDDR. By taking the observations directly from SN Ia and QSOs, one can completely eliminate the uncertainty caused by the calibration of the absolute magnitudes of standard candles (MB) and the linear sizes of standard rulers (lm). Benefit from the absence of nuisance parameters involved in other currently available methods, our analysis demonstrates no evidence for the deviation and redshift evolution of CDDR up to z = 2.3. The combination of our methodology and the machine learning Artificial Neural Network (ANN) would produce 10-3 level constraints on the violation parameter at high redshifts. Our results indicate perfect agreement between observations and predictions, supporting the persisting claims that the Etherington reciprocity theorem could still be the best description of our universe. (c) 2023 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons .org /licenses /by /4 .0/). Funded by SCOAP3.