Inhomogeneous cosmology and backreaction: Current status and future prospects

TL;DR

This paper reviews the current state and future directions of inhomogeneous cosmology and backreaction, exploring how small-scale structures might influence the large-scale evolution of the universe beyond standard models.

Contribution

It provides a comprehensive survey of the field, summarizing recent developments and outlining future research prospects in inhomogeneous cosmology.

Findings

Inhomogeneous cosmology investigates non-linear effects of small-scale structures.

Backreaction could potentially modify the large-scale dynamics of the universe.

The field is actively developing with ongoing research and debates.

Abstract

Astronomical observations reveal hierarchical structures in the Universe, from galaxies, groups of galaxies, clusters and superclusters, to filaments and voids. On the largest scales it seems that some kind of statistical homogeneity can be observed. As a result, modern cosmological models are based on spatially homogeneous and isotropic solutions of the Einstein equations, and the evolution of the universe is approximated by the Friedmann equations. In parallel to standard homogeneous cosmology, the field of inhomogeneous cosmology and backreaction is being developed. This field investigates whether small scale inhomogeneities via non-linear effects can backreact and alter the properties of the Universe on its largest scales, leading to a non-Friedmannian evolution. This paper presents the current status of inhomogeneous cosmology and backreaction. It also discusses future prospects of the field of inhomogeneous cosmology, which is based on a survey of 50 academics working in the field of inhomogeneous cosmology.