Generating matter inhomogeneities in general relativity

TL;DR

This paper explores how natural spike phenomena in general relativity can generate matter inhomogeneities in the early universe, potentially influencing large-scale structure formation.

Contribution

It demonstrates that spikes in G_2 models lead to residual matter perturbations, providing a new mechanism for inhomogeneity generation in cosmology.

Findings

Spikes cause matter overdensities due to gravitational instability.

Residual perturbations form on surfaces, not locally.

Potential impact on large-scale structure formation.

Abstract

In this Letter we discuss a natural general relativistic mechanism that causes inhomogeneities and hence generates matter perturbations in the early universe. We concentrate on spikes, both incomplete spikes and recurring spikes, that naturally occur in the initial oscillatory regime of general cosmological models. In particular, we explicitly show that spikes occurring in a class of G_2 models lead to inhomogeneities that, due to gravitational instability, leave small residual imprints on matter in the form of matter perturbations. The residual matter overdensities from recurring spikes are not local but form on surfaces. We discuss the potential physical consequences of the residual matter imprints and their possible effect on the subsequent formation of large scale structure.