Constraints on the phase plane of the dark energy equation of state

Abstract

Classification of dark energy models in the plane of w and w′, where w is the dark energy equation of state and w′ its time-derivative in units of the Hubble time, has been studied in the literature. We take the current SN Ia, CMB and BAO data, invoke a widely used parametrization of the dark energy equation of state, and obtain the constraints on the w–w′ plane. We find that several dark energy models including the cosmological constant, phantom, non-phantom barotropic fluids, and monotonic up-rolling quintessence are ruled out at the 68.3% confidence level based on the current observational data. On the other hand, down-rolling quintessence, including the thawing and the freezing models, is consistent with the current observations. All the above-mentioned models are still consistent with the data at the 95.4% confidence level.