Chaplygin gas with non-adiabatic perturbations

TL;DR

This paper explores how non-adiabatic perturbations in Chaplygin gas, due to variations in its parameter, affect the sound speed and potentially suppress oscillations in the matter power spectrum, offering insights into its internal structure.

Contribution

It introduces a novel perspective on Chaplygin gas perturbations by linking non-adiabatic effects to its internal structure and their impact on cosmological perturbations.

Findings

Non-adiabatic perturbations reduce the effective sound speed.

Reduced sound speed suppresses oscillations in the matter power spectrum.

Internal structure of Chaplygin gas influences perturbation behavior.

Abstract

Perturbations in a Chaplygin gas, characterized by an equation of state $p = -A/\rho$, may acquire non-adiabatic contributions if spatial variations of the parameter $A$ are admitted. This feature is shown to be related to a specific internal structure of the Chaplygin gas. We investigate how perturbations of this type modify the adiabatic sound speed. A reduction of the effective sound speed compared with the adiabatic value is expected to suppress oscillations in the matter power spectrum. This text is an abridged version of the following reference: W. Zimdahl and J.C. Fabris, Classical and Quantum Gravity, {\bf 22}, 4311(2005).