How the Dark Energy Can Reconcile \textit{Planck} with Local Determination of the Hubble Constant

TL;DR

The paper addresses the tension between the local H0 value and Planck+BAO-derived H0 by testing dark energy EOS evolution models, including non-parametric redshift-bin DE. Using Planck 2015 data, BAO, and the local H0 prior, it finds that a redshift-binned DE model with phantom-like behavior at very low redshift can significantly improve the fit and reconcile H0 with the local measurement, while other DE extensions offer varying degrees of improvement. The key finding is that allowing DE to evolve at low z (w0.1 ≈ -1.96, w1.5 ≈ -1.01) yields Δχ2_all ≈ -6.76 relative to ΛCDM and H0 ≈ 74 km/s/Mpc, suggesting potential new physics beyond the standard model. This work highlights the importance of late-time DE evolution in resolving cosmological tensions, contingent on the reliability of all included datasets.

Abstract

We try to reconcile the tension between the local 2.4\% determination of Hubble constant and its global determination by $\textit{Planck}$ CMB data and BAO data through modeling the dark energy variously. We find that the chi-square is significantly reduced by $Δχ^2_\text{all}=-6.76$ in the redshift-binned dark energy model where the $68\%$ limits of the equation of state of dark energy read $w(0\leq z\leq 0.1)=-1.958_{-0.508}^{+0.509}$, $w(0.1< z\leq 1.5)=-1.006_{-0.082}^{+0.092}$, and here $w(z>1.5)$ is fixed to $-1$.

Figures (4)

• Figure 1: The contour plot of $w_0$ and $w_a$ in $w_0w_a$CDM model.
• Figure 2: The plots of EOS at $z=0$ and $w_{1.5}$ in $w_{0.1}w_{1.5}$CDM model and $w_{0.25}w_{1.5}$CDM model.
• Figure 3: The contour plot of $\Omega_m$ and EOS at $z=0$ for the models extended to the $\Lambda$CDM model.
• Figure 4: Constraints on $\Omega_bh^2$ and $\Omega_ch^2$ from different DE extension of $\Lambda$CDM model.