Do the cosmological observational data prefer phantom dark energy?

TL;DR

This paper investigates whether current cosmological data favor phantom dark energy models over other models, finding a slight preference but no statistically significant difference, and explores their implications for universe evolution and structure formation.

Contribution

It provides a joint analysis of observational data to constrain phantom dark energy parameters and compares these with other dark energy models, highlighting their potential effects on cosmic evolution.

Findings

Current data slightly favor phantom dark energy but not significantly.

Phantom models predict decay of matter perturbations before the Big Rip.

Dark energy perturbations dominate gravitational effects in the future.

Abstract

The dynamics of expansion and large scale structure formation of the Universe are analyzed for models with dark energy in the form of a phantom scalar field which initially mimics a $\Lambda$-term and evolves slowly to the Big Rip singularity. The discussed model of dark energy has three parameters -- the density and the equation of state parameter at the current epoch, $\Omega_{de}$ and $w_0$, and the asymptotic value of the equation of state parameter at $a\rightarrow\infty$, $c_a^2$. Their best-fit values are determined jointly with all other cosmological parameters by the MCMC method using observational data on CMB anisotropies and polarization, SNe Ia luminosity distances, BAO measurements and more. Similar computations are carried out for $\Lambda$CDM and a quintessence scalar field model of dark energy. It is shown that the current data slightly prefer the phantom model, but the differences in the maximum likelihoods are not statistically significant. It is also shown that the phantom dark energy with monotonically increasing density in future will cause the decay of large scale linear matter density perturbations due to the gravitational domination of dark energy perturbations long before the Big Rip singularity.