Perturbation Growth in Anisotropic Cosmologies

TL;DR

This paper investigates how small fluctuations in anisotropic Bianchi type-I cosmologies grow over time, showing that under certain conditions, these perturbations become significant before the cosmological constant dominates.

Contribution

It provides a detailed analysis of perturbation growth in anisotropic cosmologies with a cosmological constant, highlighting conditions for inhomogeneity development.

Findings

Perturbations grow rapidly in anisotropic models before the cosmological constant dominates.

Growth depends on initial conditions and the magnitude of the cosmological constant.

In certain parameter ranges, inhomogeneities become significant early in the universe's evolution.

Abstract

We study the growth of perturbations in an expanding Bianchi type-I metric that evolves according to an energy density that includes dust and a cosmological constant. Assuming an epoch where the cosmological constant is subdominant, we find that, for a reasonably large set of initial conditions, the metric fluctuations grow fast enough to make the metric inhomogeneous before the cosmological constant becomes the dominant form of energy. We have examined values for the cosmological constant that are in the interval $10^{10} {GeV}$ to $10^{16} {GeV}$.