Pressure gradients, shell crossing singularities and acoustic oscillations - application to inhomogeneous cosmological models

TL;DR

This paper explores how adding pressure gradients to inhomogeneous cosmological models can prevent shell crossing singularities, enabling more realistic modeling of structure formation without singularities.

Contribution

It demonstrates that inhomogeneous pressure can avert shell crossing singularities in cosmological models, enhancing their physical plausibility.

Findings

Pressure gradients prevent shell crossing singularities.

Inhomogeneous pressure allows realistic structure formation.

Models remain well-behaved during evolution.

Abstract

Inhomogeneous cosmological models have recently become a very interesting alternative to standard cosmology. This is because these models are able to fit cosmological observations without the need for dark energy. However, due to inhomogeneity and pressure-less matter content, these models can suffer from shell crossing singularities. These singularities occur when two shell of dust collide with each other leading to infinite values of the density. In this Letter we show that if inhomogeneous pressure is included then these singularities can be prevented from occurring over the period of structure formation. Thus, a simple incorporation of a gradient of pressure allows for more comprehensive studies of inhomogeneous cosmological models and their application to cosmology.