Is the $w_0w_a$CDM cosmological parameterization evidence for dark energy dynamics partially caused by the excess smoothing of Planck CMB anisotropy data? (2410.13627v2)

Abstract: We study the performance of the spatially-flat dynamical dark energy (DE) $w_0w_a$CDM parameterization, with redshift-dependent DE fluid equation of state parameter $w(z) = w_0 + w_a z/(1+z)$, with and without a varying CMB lensing consistency parameter $A_L$, against Planck cosmic microwave background (CMB) data (P18 and lensing) and a combination of non-CMB data composed of baryonic acoustic oscillation (BAO) measurements that do not include DESI BAO data, Pantheon+ type Ia supernovae (SNIa) observations, Hubble parameter [$H(z)$] measurements, and growth factor ($f\sigma_8$) data points. From our most restrictive data set, P18+lensing+non-CMB, for the $w_0w_a$CDM+$A_L$ parameterization, we obtain $w_0=-0.879\pm 0.060$, $w_a=-0.39^{+0.26}_{-0.22}$, the asymptotic limit $w(z\to\infty) = w_0+w_a=-1.27^{+0.20}_{-0.17}$, and $A_L=1.078^{+0.036}_{-0.040}$ (all $1\sigma$ errors). This joint analysis of CMB and non-CMB data favors DE dynamics over a cosmological constant at $\sim 1\sigma$ and $A_L>1$ at $\sim 2\sigma$, i.e. more smoothing of the Planck CMB anisotropy data than is predicted by the best-fit model. For the $w_0w_a$CDM parameterization with $A_L=1$ the evidence in favor of DE dynamics is larger, $\sim 2\sigma$, suggesting that at least part of the evidence for DE dynamics comes from the excess smoothing of the Planck CMB anisotropy data. For the $w_0w_a$CDM parameterization with $A_L=1$, there is a difference of $2.8\sigma$ between P18 and non-CMB cosmological parameter constraints and $2.7\sigma$ between P18+lensing and non-CMB constraints. When $A_L$ is allowed to vary these tensions reduced to $1.9\sigma$ and $2.1\sigma$ respectively. Our P18+lensing+non-CMB data compilation positively favors the $w_0w_a$CDM parameterization without and with a varying $A_L$ parameter over the flat $\Lambda$CDM model, and $w_0w_a$CDM+$A_L$ is also positively favored over $w_0w_a$CDM.