Dynamical friction shear and rotation in Chaplygin cosmology

TL;DR

This paper investigates how dynamical friction impacts the evolution of cosmological perturbations in a universe dominated by generalized Chaplygin gas, revealing significant delays in collapse and suppression of perturbation growth.

Contribution

It extends previous work by analyzing the effects of dynamical friction within the spherical collapse model in GCG cosmology, highlighting its role in delaying collapse and suppressing perturbations.

Findings

Dynamical friction significantly delays the collapse process.

Suppression of perturbation growth is more pronounced than shear and rotation effects.

Addresses instability issues in dark-matter power spectrum studies.

Abstract

In this study, we build upon the findings of Del Popolo et al. (2013) by further analyzing the influence of dynamical friction on the evolution of cosmological perturbations within the framework of the spherical collapse model (SCM) in a Universe dominated by generalized Chaplygin gas (GCG). Specifically, we investigate how dynamical friction alters the growth rate of density perturbations, the effective sound speed, the equation-of-state parameter www, and the evolution of the cosmic expansion rate. Our results demonstrate that dynamical friction significantly delays the collapse process compared to the standard SCM. Accurate computation of these parameters is crucial for obtaining consistent results and reliable physical interpretations when employing the GCG model. Furthermore, our analysis confirms that the suppression of perturbation growth due to dynamical friction is considerably more pronounced than that caused by shear and rotation, as previously indicated by Del Popolo et al. (2013). This enhanced suppression effectively addresses the instability issues, such as oscillations or exponential divergences in the dark-matter power spectrum, highlighted in linear perturbation studies, such as those by Sandvik et al. (2004).