Perturbations in a Chaplygin gas Cosmology

TL;DR

This paper investigates how perturbations evolve in a cosmological model with radiation, dust, and Chaplygin gas, showing that unlike other dark energy models, it can support large-scale structure formation.

Contribution

It derives and solves the evolution equations for density fluctuations in a multi-fluid cosmology including Chaplygin gas, highlighting its potential to support structure formation.

Findings

Chaplygin gas allows growth of density fluctuations

Perturbation equations solved for short and long wavelengths

Supports structure formation unlike typical dark energy models

Abstract

In this paper we study the perturbations of a cosmic multi-fluid medium consisting of radiation, dust and a Chaplygin gas. To do so, we follow the 1 + 3 covariant formalism and derive the evolution equations of the fluctuations in the energy density for each species of fluid in the multi-fluid system. The solutions to these coupled systems of equations are then computed in both short-wavelength and long-wavelength modes. Our preliminary results suggest that unlike most dark energy models that discourage large-scale structure formation due to the rapid cosmological expansion (which gives little time for fluctuations to coalesce), the Chaplygin-gas model supports the formation of cosmic structures. This is manifested in the solutions of the perturbation equations which show the growth of density fluctuations over time.