Using non-DESI data to confirm and strengthen the DESI 2024 spatially-flat $w_0{w}_a$CDM cosmological parameterization result

Abstract

We use a combination of Planck cosmic microwave background (CMB) anisotropy data and non-CMB data that include Pantheon+ type Ia supernovae (SNIa), Hubble parameter [$H(z)$], growth factor ($f{\sigma }_8$) measurements, and a collection of baryon acoustic oscillation (BAO) data, but not recent DESI 2024 BAO measurements, to confirm the DESI 2024 (DESI+CMB+PantheonPlus) data compilation support for dynamical dark energy with an evolving equation of state parameter $w(z)=w_0+w_{a}z/(1+z)$. From our joint compilation of CMB and non-CMB data, in a spatially-flat cosmological model, we obtain $w_0=-0.850\pm 0.059$ and $w_a=-0.59_{-0.22}^{+0.26}$ and find that this dynamical dark energy is favored over a cosmological constant by $\sim 2\sigma$. Our data constraints on the flat $w_0{w}_a$CDM parameterization are slightly more restrictive than the DESI 2024 constraints, with the DESI 2024 and our values of $w_0$ and $w_a$ differing by $-0.27\sigma$ and $0.44\sigma$, respectively. Our data compilation slightly more strongly favors the flat $w_0{w}_a$CDM model over the flat $\Lambda$CDM model than does the DESI 2024 data compilation. We note that our CMB and non-CMB data $w_0{w}_a$CDM parameterization cosmological constraints are discrepant at 2.7$\sigma$, a little larger than the 1.9$\sigma$ discrepancy between DESI DR1 BAO and CMB data flat $\Lambda$CDM model cosmological constraints. We also show that if we remove the Pantheon+ SNIa contribution from the non-CMB data, for the $w_0{w}_a$CDM parameterization we still find tension between P18 and non-CMB data (2.5$\sigma$) and P18+lensing and non-CMB data (2.4$\sigma$). Even after the exclusion of Pantheon+ SNIa data the $\Lambda$CDM model is still disfavoured at $\sim 2\sigma$ c.l.

Comments: 13 pages, 6 figures. Accepted for publication in Physical Review D