Observational constraints on inhomogeneous cosmological models without dark energy

TL;DR

This paper investigates how large-scale inhomogeneities, such as voids, influence cosmological observations and assesses the observational constraints on models without dark energy, including both Copernican and non-Copernican scenarios.

Contribution

It analyzes the observational constraints on inhomogeneous cosmological models, especially large voids, and evaluates their viability as alternatives to dark energy.

Findings

Copernican models are constrained to small corrections to observables.

Non-Copernican models with large voids can mimic accelerated expansion.

Observational tests can exclude certain inhomogeneous models.

Abstract

It has been proposed that the observed dark energy can be explained away by the effect of large-scale nonlinear inhomogeneities. In the present paper we discuss how observations constrain cosmological models featuring large voids. We start by considering Copernican models, in which the observer is not occupying a special position and homogeneity is preserved on a very large scale. We show how these models, at least in their current realizations, are constrained to give small, but perhaps not negligible in certain contexts, corrections to the cosmological observables. We then examine non-Copernican models, in which the observer is close to the center of a very large void. These models can give large corrections to the observables which mimic an accelerated FLRW model. We carefully discuss the main observables and tests able to exclude them.