Limits on the Dark Energy Parameters from Cosmic Microwave Background experiments

Abstract

Full suite of the present day Cosmic Microwave background (CMB) data, when combined with weak prior information on the Hubble constant and the age of the Universe, or the Large-Scale structure, provides strong indication for a non-zero density of the vacuum-like dark energy in our universe. This result independently supports the conclusions from Supernovae Ia (SN1a) data. When the model parameter space is extended to allow for the range of the equation of state parameter w_Q for the dynamical field Q which gives rise to dark energy, the CMB data is found to give a weak upper bound w_Q < -0.4 at 95% CL, however combined with SN1a data it strongly favours w_Q < -0.8, consistent with Lambda-term like behaviour.