Effect of cosmic backreaction on the future evolution of an accelerating universe

TL;DR

This paper explores how inhomogeneities in the universe influence its future acceleration, showing that backreaction can slow or reverse acceleration, potentially leading to a decelerating epoch.

Contribution

It introduces a two-scale model within the Buchert framework to analyze the impact of inhomogeneities on the universe's future evolution, considering observed acceleration as input.

Findings

Backreaction can slow down future acceleration.

Inhomogeneities may lead to a future decelerating epoch.

The event horizon influences the global acceleration.

Abstract

We investigate the effect of backreaction due to inhomogeneities on the evolution of the present universe by considering a two-scale model within the Buchert framework. Taking the observed present acceleration of the universe as an essential input, we study the effect of inhomogeneities in the future evolution. We find that the backreaction from inhomogeneities causes the acceleration to slow down in the future for a range of initial configurations and model parameters. The present acceleration ensures formation of the cosmic event horizon, and our analysis brings out how the effect of the event horizon could further curtail the global acceleration, and even lead in certain cases to the emergence of a future decelerating epoch.