A First Observational Assessment of Cosmic Backreaction Over an Extended Redshift Range

Abstract

In the recent preprint arXiv:2604.07244v1, the authors introduce a novel combination of redshift, distance, and expansion rate observables for constraining cosmic backreaction observationally. The current work presents a first application of the method, in principle yielding the first direct constraints on the total cosmic backreaction in our universe over a significant redshift range. However, we find that current data are not yet sufficient to place tight constraints on backreaction. Thus, neither vanishing nor significant backreaction can be ruled out with the presented constraints. Nonetheless, the results suggest that forthcoming survey data will enable enlightening constraints on cosmic backreaction using this method.

Addendum to "Observational Tests for Distinguishing Classes of Cosmological Models'' (arXiv:2604.07244v1). v2: 1 figure added and text slightly extended. Matches version accepted for publication in PRD