The case for dynamical dark energy revisited

Abstract

We investigate the behaviour of dark energy using the recently released supernova data of Riess et al 2004 and a model independent parametrization for dark energy (DE). We find that, if no priors are imposed on Ω_0m and h, DE which evolves with time provides a better fit to the SNe data than ΛCDM. This is also true if we include results from the WMAP CMB data. From a joint analysis of SNe + CMB, the best fit DE model has w₀ ≲−1 at the present epoch and the transition from deceleration to acceleration occurs at z_T=0.39 ± 0.03. However, DE evolution becomes weaker if the ΩCDM based CMB results Ω_0m=0.27 ± 0.04, h=0.71 ± 0.06 are incorporated in the analysis. In this case, z_T=0.57 ± 0.07. Our results also show that the extent of DE evolution is sensitive to the manner in which the supernova data is sampled.