New Isotropic and Anisotropic Sudden Singularities

TL;DR

This paper explores new types of finite-time singularities in isotropic and anisotropic cosmological models, identifying conditions under which they occur and proposing energy conditions to exclude them.

Contribution

It introduces a new class of finite-time singularities in cosmology and analyzes their occurrence in various anisotropic models, providing specific examples and conditions.

Findings

Existence of infinite families of finite-time singularities in isotropic universes.

Conditions under which anisotropic sudden singularities can form.

Identification of energy conditions needed to exclude these singularities.

Abstract

We show the existence of an infinite family of finite-time singularities in isotropically expanding universes which obey the weak, strong, and dominant energy conditions. We show what new type of energy condition is needed to exclude them ab initio. We also determine the conditions under which finite-time future singularities can arise in a wide class of anisotropic cosmological models. New types of finite-time singularity are possible which are characterised by divergences in the time-rate of change of the anisotropic-pressure tensor. We investigate the conditions for the formation of finite-time singularities in a Bianchi type $VII_{0}$ universe with anisotropic pressures and construct specific examples of anisotropic sudden singularities in these universes.