New Anisotropic Sudden Singularities and Dimensional Reduction

TL;DR

This paper introduces a new class of finite-time singularities in anisotropic cosmological models, revealing how directional divergences in pressure can cause dimensional reduction effects.

Contribution

It demonstrates the existence of anisotropic sudden singularities with constant scale factors and explores their implications for dimensional reduction in Bianchi type IX universes.

Findings

Existence of non-simultaneous anisotropic sudden singularities.

Divergences in pressures lead to dimensional reduction effects.

Singularities occur with constant scale factor, expansion rate, and density.

Abstract

We demonstrate the existence of sudden, finite-time, singularities, with constant scale factor, expansion rate and density, in expanding Bianchi type IX universes with free anisotropic pressures. A new type of non-simultaneous anisotropic sudden singularity arises because of the divergences of the pressures, which may be of barrel or pancake type. The effect of one or more directions of expansion hitting a sudden singularity is tantamount to dimensional reductions as the non-singular directions continue expanding and can see the sudden singularity in their past.