New Constraints On The Dark Energy Equation of State

TL;DR

This paper combines multiple cosmological observations to constrain the dark energy equation of state w(z), finding no significant deviation from a cosmological constant but slight indications of w<-1 at low redshift.

Contribution

It introduces a principal components approach to analyze combined datasets for dark energy, providing new constraints on w(z) over 0<z<2.

Findings

No significant deviation from a cosmological constant.

Slight indication for w<-1 at low redshift.

Some alternative models may be in tension with the data.

Abstract

We combine recent measurements of Cosmic Microwave Background Anisotropies, Supernovae luminosity distances and Baryonic Acoustic Oscillations to derive constraints on the dark energy equation of state w in the redshift range 0<z<2, using a principal components approach. We find no significant deviations from the expectations of a cosmological constant. However, combining the datasets we find slight indication for w<-1 at low redshift, thus highlighting how these datasets prefer a non-constant w. Nevertheless the cosmological constant is still in agreement with these observations, while we find that some classes of alternative models may be in tension with the inferred w(z) behaviour.