Interpretation of SNIa and BAO cosmic probes results using a two-regions model of the universe

Abstract

This article revisits the interpretation of cosmic probes such as SNIa and BAO under a two-regions model of the universe. Standard cosmological analyses assume homogeneity, yet observations are predominantly conducted in overdense regions where matter is clustered, potentially biasing conclusions about cosmic expansion. We refine an existing two-regions framework that accounts for both overdense and underdense areas, demonstrating that the apparent acceleration of the universe, typically attributed to dark energy, can emerge as a consequence of observational bias rather than a fundamental cosmological constant. By applying this model to SNIa and BAO measurements, we show that inhomogeneities can affect redshift and distance estimates in a way that mimics cosmic acceleration. This interpretation provides a natural resolution to the coincidence problem and offers an alternative explanation for the observed tensions in Hubble constant measurements. Additionally, it may shed light on the unexpectedly early formation of galaxies observed by JWST. These findings challenge the necessity of dark energy and suggest that the observed acceleration may be an artefact of the spatial distribution of matter rather than a true universal phenomenon.