Abstract
We investigate the behaviour of dark energy using the recentlyreleased supernova data of Riess et al 2004 and a modelindependent parametrization for dark energy (DE). We findthat, if no priors are imposed on Ω0m and h, DEwhich evolves with time provides a better fit to the SNe datathan ΛCDM. This is also true if we include results fromthe WMAP CMB data. From a joint analysis of SNe + CMB, thebest fit DE model has w0 ≲ −1 at the present epoch andthe transition from deceleration to acceleration occurs at zT = 0.39 ± 0.03. However, DE evolution becomes weaker if theΛCDM based CMB results Ω0m = 0.27 ± 0.04, h = 0.71 ± 0.06 are incorporated in the analysis. Inthis case, zT = 0.57 ± 0.07. Our results also show that theextent of DE evolution is sensitive to the manner in which thesupernova data is sampled.
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