Cosmology-Independent Constraints on the Etherington Relation and SNeIa Absolute Magnitude Evolution from DESI-DR2

TL;DR

This paper tests the Etherington relation using DESI-DR2 and SNeIa data, confirming its validity and constraining SNeIa magnitude evolution, thus supporting metric gravity and photon conservation.

Contribution

It provides the first comprehensive test of the Etherington relation with DESI-DR2 data and constrains SNeIa absolute magnitude evolution.

Findings

Measurements are consistent with the Etherington relation.

Constraints on SNeIa magnitude evolution: dM/dz = 0.07 ± 0.07.

Supports the metric nature of gravity and photon number conservation.

Abstract

We carry out a test of the fundamental Etherington relation (cosmic distance duality relation) which relates the luminosity distance $D_{\rm L}$ and angular diameter distance $D_{\rm A}$ in metric theories of gravity. We use the latest measurements of the angular diameter distance as a function of redshift from the Dark Energy Spectroscopic Instrument Data Release 2 (DESI-DR2) and the luminosity distance from a variety of compilations of Supernovae of Type Ia (SNeIa). Our results indicate that these measurements are statistically consistent with the Etherington relation. In addition to providing a confirmation of the underlying assumptions of the Etherington relation, i.e., the metric nature of gravity, Lorentz invariance and photon number conservation, our results are also a stringent test of any residual systematic effects. We interpret the absence of evidence of any deviation from this relation to constrain the evolution of the absolute magnitude of SNeIa to $dM/dz = 0.07 \pm 0.07$ over and above the systematics that are already accounted for in the SNeIa analyses. We discuss how the Etherington relation can be used to constrain systematic parameters in the analyses of dynamical dark energy using geometric probes, to make it more robust against systematic effects.