Dark-fluid constraints of shear-free universes

TL;DR

This paper investigates the integrability conditions for shear-free universes dominated by dark fluids, focusing on linearized perturbations and the Chaplygin gas model to understand their evolution and constraints.

Contribution

It introduces new integrability conditions for shear-free dark-fluid universes, especially in the context of Chaplygin gas and linearized perturbations.

Findings

Derived conditions for the existence of shear-free quasi-Newtonian and anti-Newtonian spacetimes.

Analyzed the evolution constraints for universes with Chaplygin gas.

Provided insights into the stability of shear-free dark-fluid cosmologies.

Abstract

Integrability conditions arising from general irrotational fluid-flow considerations of a universe dominated by cosmic dark fluids will be investigated under special assumptions on the nature of the spacetime shear. Special emphasis will be placed on linearized perturbations of quasi-Newtonian and anti-Newtonian spacetimes, whereby the conditions for the existence and consistent evolution of such spacetimes in the presence of the Chaplygin gas fluid model will be derived and discussed.