Cosmic geometry rule survives another careful test

The distance-duality relation links how bright objects appear to how large they appear on the sky — any violation would signal exotic physics like photon loss or non-metric gravity. Using 38 galaxy clusters matched to Type Ia supernovae from the Pantheon+ catalog, the analysis simultaneously tests for distance-duality breakdown and for redshift evolution in supernova brightness. Both violation parameters are consistent with zero at 68% confidence, and the results hold when stricter matching criteria or DESI BAO data are added. A cosmology-independent supernova absolute magnitude calibration of M₀ = −19.46 mag emerges as a byproduct.