Soft singularity crossing and transformation of matter properties

TL;DR

This paper explores cosmological models with soft singularities, demonstrating smooth crossings enabled by matter property transformations, and shows some models align with supernova data, revealing complex evolution including recollapse and Big Crunch.

Contribution

It introduces a method for smooth crossing of soft singularities in tachyon and fluid models via matter property transformations, with numerical analysis and observational compatibility.

Findings

Models with anti-Chaplygin gas or specific tachyons can cross soft singularities smoothly.

Numerical simulations show a universe undergoing recollapse after crossing singularities.

Some models are compatible with supernova observational data.

Abstract

We investigate particular cosmological models, based either on tachyon fields or on perfect fluids, for which soft future singularities arise in a natural way. Our main result is the description of a smooth crossing of the soft singularity in models with an anti-Chaplygin gas or with a particular tachyon field in the presence of dust. Such a crossing is made possible by certain transformations of matter properties. Some of these cosmological evolutions involving tachyons are compatible with SNIa data. We compute numerically their dynamics involving a first soft singularity crossing, a turning point and a second soft singulatity crossing during recollapse, ending in a Big Crunch singularity.