Mixmaster Fluids Near the Big Bang

TL;DR

This study numerically investigates the behavior of fluids near the Big Bang in certain cosmological models, revealing oscillatory dynamics and inhomogeneities consistent with the BKL conjecture.

Contribution

First numerical evidence showing fluid velocity oscillations in inhomogeneous cosmologies align with the BKL conjecture near singularities.

Findings

Fluid velocity develops mixmaster-like oscillations.

Oscillations lead to inhomogeneities in matter density.

Dynamics are local and oscillatory near the singularity.

Abstract

We numerically study the approach to the singularity in $\mathbb{T}^{2}$-symmetric cosmological spacetimes containing a non-stiff perfect fluid satisfying a linear equation of state $p=K\rho$, $K \in [0,1)$. Near the singularity, the dynamics are found to be local and oscillatory. In particular, our results show, for the first time, that the fluid velocity in inhomogeneous cosmologies develops mixmaster-esque oscillations consistent with the generalised BKL conjecture of Uggla et al. Moreover, we find these fluid oscillations are responsible for the development of local inhomogeneities in the matter density of the early universe.