Modelling Time-varying Dark Energy with Constraints from Latest Observations

Understand

We introduce a set of two-parameter models for the dark energy equation of state (EOS) $w(z)$ to investigate time-varying dark energy.

• The models are classified into two types according to their boundary behaviors at the redshift $z=(0,\infty)$ and their local extremum properties.
• A joint analysis based on four observations (SNe + BAO + CMB + $H_0$) is carried out to constrain all the models.
• It is shown that all models get almost the same $\chi^2_{min}\simeq 469$ and the cosmological parameters $(\Omega_M, h, \Omega_bh^2)$ with the best-fit results $(0.28, 0.70, 2.24)$, although the constraint results on two parameters $(w_0, w_1)$ and the allowed regions for the EOS $w(z)$ are sensitive to different models and a given extra model parameter.