$w$-cosmological singularities

TL;DR

This paper characterizes specific weak singularities in homogeneous isotropic cosmological models where the barotropic index becomes singular due to the scale factor's Taylor series expansion lacking linear and quadratic terms.

Contribution

It provides a detailed analysis of barotropic index singularities and their relation to the analyticity of the scale factor in cosmological models.

Findings

Singularities occur when the scale factor's Taylor series omits linear and quadratic terms.

Barotropic index becomes singular at these points, but the singularities are weak.

Density and pressure remain regular despite the singularity in the barotropic index.

Abstract

In this paper we characterize barotropic index singularities of homogeneous isotropic cosmological models. They are shown to appear in cosmologies for which the scale factor is analytical with a Taylor series in which the linear and quadratic terms are absent. Though the barotropic index of the perfect fluid is singular, the singularities are weak, as it happens for other models for which the density and the pressure are regular.