Structure formation as an alternative to dark energy and modified gravity

TL;DR

This paper explores how the formation of cosmic structures might explain the universe's accelerated expansion without invoking dark energy or modified gravity, emphasizing the importance of non-linear inhomogeneities.

Contribution

It proposes a semi-realistic model showing how structure formation can naturally lead to accelerated expansion, challenging the need for new physics.

Findings

Structure formation can cause apparent acceleration.

A model where structure physics determines expansion rate.

Highlights importance of inhomogeneities in cosmology.

Abstract

Observations are inconsistent with a homogeneous and isotropic universe with ordinary matter and gravity. The universe is far from exact homogeneity and isotropy at late times, and the effect of the non-linear structures has to be quantified before concluding that new physics is needed. We explain how structure formation can lead to accelerated expansion, and discuss a semi-realistic model where the timescale of the change in the expansion rate emerges from the physics of structure formation.