On astrophysical explanations due to cosmological inhomogeneities for the observational acceleration

TL;DR

This paper reviews inhomogeneous cosmological models, such as local voids and backreaction effects, assessing their ability to explain the observed acceleration without a cosmological constant, and finds most are inconsistent with multiple observational constraints.

Contribution

It critically evaluates the viability of inhomogeneous cosmological models as alternatives to dark energy, highlighting their limitations based on current observational data.

Findings

Many inhomogeneous models are ruled out by observations

Averaged models require high perturbation amplitudes to produce acceleration

Effective Lambda values in models do not match observed acceleration

Abstract

We review various cosmological models with a local underdense region (local void) and the averaged models with the backreaction of inhomogeneities, which have been proposed to explain (without assuming a positive cosmological constant) the observed accelerating behaviors appearing in the magnitude-redshift relation of SNIa. To clarify their reality, we consider their consistency with the other observational studies such as CMB temperature anisotropy, baryon acoustic oscillation, kinematic Sunyaev-Zeldovich effect, and so on. It is found as a result that many inhomogeneous models seem to be ruled out and only models with the parametrs in the narrow range remain to be examined, and that, unless we assume very high amplitudes of perturbations or gravitational energies, the averaged models cannot have the accelerated expansion and the fitted effective Lambda has not the value necessary for the observed acceleration.