Sudden Future Singularities

TL;DR

This paper demonstrates that sudden future singularities can occur in expanding Friedmann universes under certain conditions, even with positive density and pressure, and provides criteria to exclude such unphysical scenarios.

Contribution

It introduces explicit examples of sudden future singularities and offers a simple condition to identify and eliminate these unphysical behaviors.

Findings

Sudden future singularities can occur with positive density and pressure.

Explicit examples of such singularities are constructed.

A criterion is provided to exclude unphysical singular behaviors.

Abstract

We show that a singularity can occur at a finite future time in an expanding Friedmann universe even when the density is positive and the density plus the sum of the principal pressures is positive. Explicit examples are constructed and a simple condition is given which can be used to eliminate behaviour of this sort if it is judged to be unphysical.