Inhomogeneous cosmological models: exact solutions and their applications

TL;DR

This paper reviews recent developments in inhomogeneous cosmological models, emphasizing their importance as exact perturbations of homogeneous models for analyzing precise cosmological observations.

Contribution

It clarifies that inhomogeneous models are not alternatives but essential perturbations of FLRW models, highlighting their growing role in modern cosmology.

Findings

Inhomogeneous models are exact perturbations of FLRW models.

Inhomogeneities are crucial for analyzing future precise observations.

Recent developments emphasize the importance of inhomogeneous frameworks.

Abstract

Recently, inhomogeneous generalisations of the Friedmann-Lemaitre-Robertson-Walker cosmological models have gained interest in the astrophysical community and are more often employed to study cosmological phenomena. However, in many papers the inhomogeneous cosmological models are treated as an alternative to the FLRW models. In fact, they are not an alternative, but an exact perturbation of the latter, and are gradually becoming a necessity in modern cosmology. The assumption of homogeneity is just a first approximation introduced to simplify equations. So far this assumption is commonly believed to have worked well, but future and more precise observations will not be properly analysed unless inhomogeneities are taken into account. This paper reviews recent developments in the field and shows the importance of an inhomogeneous framework in the analysis of cosmological observations.