Chaplygin gas with non-adiabatic pressure perturbations

TL;DR

This paper explores how non-adiabatic pressure perturbations in Chaplygin gas, due to spatial variations of its parameter, affect cosmic microwave background anisotropies through modifications in sound speed and gravitational potential evolution.

Contribution

It introduces a novel analysis of non-adiabatic perturbations in Chaplygin gas and their impact on cosmological observables, linking internal structure to perturbation behavior.

Findings

Non-adiabatic contributions alter the sound speed in Chaplygin gas.

Perturbations influence the evolution of gravitational potential.

Impacts on the Integrated Sachs-Wolfe effect are demonstrated.

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 and influence the time dependence of the gravitational potential which gives rise to the Integrated Sachs-Wolfe effect in the anisotropy spectrum of the cosmic microwave background.