Time Asymmetry and Chaos in General Relativity

TL;DR

This paper investigates the late-time behavior of Bianchi type VIII cosmological models, revealing a transition from initial chaos to non-chaotic evolution and exploring why different analytical methods yield contrasting results on their time symmetry.

Contribution

The study demonstrates that Bianchi type VIII models evolve from chaotic to non-chaotic states at late times and analyzes the reasons behind differing conclusions from various approximation methods.

Findings

Late-time evolution is non-chaotic in these models.

Different approximation methods can lead to contrasting conclusions.

The BKL approximation aligns with the non-chaotic late-time behavior.

Abstract

In this work the late-time evolution of Bianchi type $VIII$ models is discussed. These cosmological models exhibit a chaotic behaviour towards the initial singularity and our investigations show that towards the future, far from the initial singularity, these models have a non-chaotic evolution, even in the case of vacuum and without inflation. These space-time solutions turn out to exhibit a particular time asymmetry. On the other hand, investigations of the late-time behaviour of type $VIII$ models by another author have the result that chaos continues for ever in the far future and that these solutions have a time symmetric behaviour: this result was obtained using the approximation methods of Belinski, Khalatnikov and Lifshitz ($BKL$) and we try to find out a possible reason explaining why the different approaches lead to distinct outcomes. It will be shown that, at a heuristic level, the $BKL$ method gives a valid approximation of the late-time evolution of type $VIII$ models, agreeing with the result of our investigations.