Cosmic Inhomogeneities and the Average Cosmological Dynamics

TL;DR

This paper investigates whether inhomogeneities in the universe can account for cosmic acceleration through averaging effects, concluding that such effects are negligible and cannot explain the observed acceleration.

Contribution

It demonstrates that averaging inhomogeneities in a realistic cosmological model does not significantly alter the universe's expansion dynamics, challenging the idea that inhomogeneities explain dark energy.

Findings

Averaging effects are negligible in realistic models.

Inhomogeneities do not account for cosmic acceleration.

Modified Einstein equations from averaging are insufficient.

Abstract

If general relativity (GR) describes the expansion of the Universe, the observed cosmic acceleration implies the existence of a `dark energy'. However, while the Universe is on average homogeneous on large scales, it is inhomogeneous on smaller scales. While GR governs the dynamics of the \emph{in}homogeneous Universe, the averaged \emph{homogeneous} Universe obeys modified Einstein equations. Can such modifications alone explain the acceleration? For a simple generic model with realistic initial conditions, we show the answer to be `no'. Averaging effects negligibly influence the cosmological dynamics.