Backreaction in late-time cosmology

TL;DR

This paper reviews how nonlinear structure formation might influence the universe's expansion and observations, potentially explaining cosmic acceleration without dark energy or modified gravity.

Contribution

It provides a comprehensive review of backreaction effects in late-time cosmology, emphasizing physical mechanisms and unresolved issues.

Findings

Backreaction could impact cosmic expansion rates.

Nonlinear structures may affect light propagation.

Open questions remain about the significance of these effects.

Abstract

We review the effect of the formation of nonlinear structures on the expansion rate, spatial curvature and light propagation in the universe, focusing on the possibility that it could explain cosmological observations without the introduction of dark energy or modified gravity. We concentrate on explaining the relevant physics and highlighting open questions.