Tilt and phantom cosmology

TL;DR

This paper demonstrates that in certain tilting perfect fluid cosmological models with ultra-radiative equations of state, the tilt becomes extreme, leading to finite-time singularities similar to phantom cosmology but without exotic matter.

Contribution

It shows that tilt instability in these models causes finite-time singularities, providing a new perspective on late-time cosmological behavior without exotic matter.

Findings

Tilt becomes extreme at late times in these models.

Observers experience finite-time singularities due to tilt instability.

Behavior mimics phantom cosmology without exotic matter.

Abstract

We show that in tilting perfect fluid cosmological models with an ultra-radiative equation of state, generically the tilt becomes extreme at late times and, as the tilt instability sets in, observers moving with the tilting fluid will experience singular behaviour in which infinite expansion is reached within a finite proper time, similar to that of phantom cosmology (but without the need for exotic forms of matter).