Dark Energy and Fate of the Universe

TL;DR

This paper introduces a new dark energy parametrization to analyze the universe's fate, constrains it with current data, and predicts possible scenarios including a big rip in at least 16.7 billion years.

Contribution

It proposes a divergence-free dark energy parametrization that accurately models behavior at all redshifts and constrains the universe's future using observational data.

Findings

Universe can last at least 16.7 billion years before a big rip.

Bound systems are destroyed before the big rip, depending on orbital period.

The new parametrization covers a wide range of dark energy models.

Abstract

We explore the ultimate fate of the Universe by using a divergence-free parametrization for dark energy $w(z)=w_0+w_a({\ln (2+z)\over 1+z}-\ln2)$. Unlike the CPL parametrization, this parametrization has well behaved, bounded behavior for both high redshifts and negative redshifts, and thus can genuinely cover many theoretical dark energy models. After constraining the parameter space of this parametrization by using the current cosmological observations, we find that, at the 95.4% confidence level, our Universe can still exist at least 16.7 Gyr before it ends in a big rip. Moreover, for the phantom energy dominated Universe, we find that a gravitationally bound system will be destroyed at a time $t \simeq P\sqrt{2|1+3w(-1)|}/[6\pi |1+w(-1)|]$, where $P$ is the period of a circular orbit around this system, before the big rip.