Constraints on redshift-binned dark energy using DESI BAO data
Ye-Huang Pang, Xue Zhang, Qing‐Guo Huang
Abstract
We parametrize the equation of state of late-time dark energy as ${w}_{\mathrm{bin}}(z)$, with three redshift bins, characterized by a constant equation of state in each bin. Then, we constrain the parameters of the ${w}_{\mathrm{bin}}\mathrm{CDM}$ model using datasets from Dark Energy Spectroscopy Instrument baryon acoustic oscillations data, Planck cosmic microwave background power spectrum, ACT DR6 lensing power spectrum, and type Ia supernova distance-redshift data of Pantheon Plus/DES Y5/Union3. The significances for ${w}_{1}>\ensuremath{-}1$ are $1.9\ensuremath{\sigma}$, $2.6\ensuremath{\sigma}$ and $3.3\ensuremath{\sigma}$, and ${w}_{2}$ is consistent with $\ensuremath{-}1$ within $1\ensuremath{\sigma}$ level, while $1.6\ensuremath{\sigma}$, $1.5\ensuremath{\sigma}$ and $1.5\ensuremath{\sigma}$ for ${w}_{3}<\ensuremath{-}1$ in these three data combinations with different choices of type Ia supernova datasets, respectively. Additionally, to alleviate ${H}_{0}$ tension, we incorporate the early dark energy (EDE) model in the early-time universe and add the SH0ES absolute magnitude ${M}_{b}$ prior (or ${H}_{0}$ prior) to further constrain the ${w}_{\mathrm{bin}}\mathrm{EDE}$ model. In the ${w}_{\mathrm{bin}}\mathrm{EDE}$ model, we find a ${w}_{\mathrm{bin}}(z)$ pattern similar to that in the ${w}_{\mathrm{bin}}\mathrm{CDM}$ model. The results of the three data combinations exhibit ${w}_{1}>\ensuremath{-}1$ at $1.7\ensuremath{\sigma}$, $1.7\ensuremath{\sigma}$ and $2.9\ensuremath{\sigma}$ level, meanwhile ${w}_{3}<\ensuremath{-}1$ at $1.3\ensuremath{\sigma}$, $1.3\ensuremath{\sigma}$ and $1.3\ensuremath{\sigma}$ level, respectively. In all, our results indicate that the transition of dark energy from phantom at high redshifts to quintessence at low redshifts is not conclusive.