A model-independent test of the cosmic distance-duality relation using galaxy clusters and type Ia supernovae matched pairs

Context. The cosmic distance-duality relation (CDDR), D L / D A (1 + z ) −2 = 1, is a fundamental premise in observational cosmology, linking the luminosity distance ( D L ) and angular diameter distance ( D A ). Any departure from this relation would point to new physics such as photon nonconservation, opacity, or nonmetric gravity. Aims. We performed a stringent, model-independent test of the CDDR using the latest observational data. We additionally assessed the robustness of the matched-pair analysis against matching tolerance and supplemented the baseline analysis with Dark Energy Spectroscopic Instrument (DESI) baryon acoustic oscillation (BAO) measurements. We aim to address the degeneracy between cosmic opacity and the source evolution of type Ia supernovae (SNe Ia) to provide robust constraints on the Etherington reciprocity theorem. Methods. We utilized a matched sample of 38 galaxy clusters from the Bonamente et al. (2006, ApJ, 647, 25) compilation and SNe Ia from the Pantheon+ compilation. To avoid cosmological model dependence, we employed the matched pair technique, pairing D A and D L at identical redshifts. We adopted a joint likelihood analysis that simultaneously constrains the CDDR-violation parameter η and a possible redshift evolution of the SNe Ia absolute magnitude, parameterized as M B ( z ) = M 0 + εz . We propagated the sub-covariance matrix extracted from the Pantheon+ compilation and implemented a split-normal likelihood to preserve the asymmetric cluster uncertainties. We then repeated the analysis with a stricter matching threshold, Δ D C / D C = 3%, and extended the dataset by including four DESI 2024 BAO measurements of D M / r d . For the BAO extension, we considered both a free- r d case and a case with a Planck prior on r d . Results. Our analysis yields η = 0.050 +0.348 −0.0307 and ε = −0.184 +0.724 −0.574 (68% confidence level), showing no statistically significant evidence for CDDR violation or SNe Ia evolution. Tightening the matching tolerance to 3% leaves our conclusions unchanged. Including DESI BAO data does not qualitatively modify the inferred parameters. When r d is treated as a free parameter, we find r d = 140.56 +8.12 −8.11 . In contrast, imposing a Planck prior yields r d = 147.078 ± 0.259. In all cases, both η = 0 and ε = 0 remain consistent with the data. Additionally, we derive a cosmology-independent calibration of M 0 = −19.460 +0.126 −0.124 mag, consistent with local SH0ES measurements. Conclusions. The standard cosmological framework remains robust under this model-independent scrutiny. Our results are stable against variations in the matching tolerance and when including current DESI BAO data. We further find that exploratory spline reconstructions introduce additional nonphysical degeneracies in the present data regime, so that the matched-pair framework remains the most transparent and stable method for this analysis. By effectively breaking the degeneracy between opacity and evolution, our method offers a reliable pathway for future precision tests using larger samples from upcoming surveys.