Reconstruction of the Dark Energy Equation of State from the Latest Observations

Abstract

Since the discovery of the accelerating expansion of our universe in 1998, studying the features of dark energy has remained a hot topic in modern cosmology. In the literature, dark energy is usually described by w  ≡  P / ρ , where P and ρ denote its pressure and energy density. Therefore, exploring the evolution of w is the key approach to understanding dark energy. In this work, we adopt three different methods, polynomial expansion, principal component analysis, and the correlated prior method, to reconstruct w with a collection of the latest observations, including the type-Ia supernova, cosmic microwave background, large-scale structure, Hubble measurements, and baryon acoustic oscillations (BAOs), and find that the concordance cosmological constant model ( w  = −1) is still safely consistent with these observational data at the 68% confidence level. However, when we add the high-redshift BAO measurement from the Ly α forest (Ly α FB) of BOSS DR11 quasars into the calculation, there is a significant impact on the reconstruction result. In the standard ΛCDM model, since the Ly α FB data slightly prefer a negative dark energy density, in order to avoid this problem, a dark energy model with a w significantly smaller than −1 is needed to explain this Ly α FB data. In this work, we find the consistent conclusion that there is a strong preference for the time-evolving behavior of dark energy w at high redshifts, when including the Ly α FB data. Therefore, we think that this Ly α FB data needs to be watched carefully attention when studying the evolution of the dark energy equation of state.