Description of our cosmological spacetime as a perturbed conformal Newtonian metric and implications for the backreaction proposal for the accelerating universe

TL;DR

This paper examines whether large inhomogeneities in a dust universe can alter observable predictions, challenging the idea that such inhomogeneities do not affect the universe's acceleration interpretation.

Contribution

It analyzes conditions under which large spatial variations can invalidate the assumption that inhomogeneities do not impact observables in a perturbed conformal Newtonian framework.

Findings

Large spatial variations can affect the validity of the perturbed conformal Newtonian metric

Conditions identified where inhomogeneities influence cosmological observables

Implications for the backreaction proposal in explaining cosmic acceleration

Abstract

It has been argued that the spacetime of our universe can be accurately described by a perturbed conformal Newtonian metric, and hence even large density inhomogeneities in a dust universe can not change the observables predicted by the homogeneous dust model. In this paper we study a spherically symmetric dust model and illustrate conditions under which large spatial variations in the expansion rate can invalidate the argument.