Comparing the scalar-field dark energy models with recent observations

Abstract

We focus on a class of scalar-field dark energy models (i.e., ϕCDM models) which behave like cosmological trackers at early times, and investigate the general properties of them. Particularly, we choose three ϕCDM models with typical potentials, i.e., V(ϕ)∝ϕ−α (inverse power-law (IPL) model), V(ϕ)∝cothαϕ (L-model) and V(ϕ)∝cosh(αϕ) (Oscillatory tracker model), where the latter two models are based on the α-attractors originated from the study of inflation. These models, which reduce to the ΛCDM model with α→0, are studied and compared with the recent observations, including the Pantheon sample of type Ia supernovae (SNe Ia), baryon acoustic oscillations (BAO) measurements extracted from 6dFGS, BOSS and eBOSS, as well as the temperature and polarization anisotropy power spectra data of cosmic microwave background radiation (CMB) from Planck 2018 results. The observational constraints from the combining sample (SNe Ia + BAO + CMB) indicate that none of the three ϕCDM models exclude the ΛCDM model at 68.3% confidence level. We find that the CMB anisotropy data have obvious advantages in constraining the dark energy models compared with other cosmological probes, which is particularly evident in the L-model. Furthermore, we apply the Bayesian evidence to compare the ϕCDM models and the ΛCDM model with the analysis of the combining sample. The concordance ΛCDM model is still the most supported one. In addition, among the three ϕCDM models, the IPL model is the most competitive one, while the L-model/Oscillatory tacker model is moderately/strongly disfavored.