Instability of Spacelike and Null Orbifold Singularities

TL;DR

This paper demonstrates that simple models of cosmological singularities in spacetime orbifolds are inherently unstable, as even a single particle can induce a catastrophic collapse to a Big Crunch.

Contribution

It reveals the instability of spacelike and null orbifold singularities when perturbed by particles, challenging their use as simple cosmological models.

Findings

Single particles trigger collapse to strong curvature singularity

Instability persists far from the particle

Orbifold models are not stable under perturbations

Abstract

Time dependent orbifolds with spacelike or null singularities have recently been studied as simple models of cosmological singularities. We show that their apparent simplicity is an illusion: the introduction of a single particle causes the spacetime to collapse to a strong curvature singularity (a Big Crunch), even in regions arbitrarily far from the particle.