Can interacting dark energy solve the $H_0$ tension?

TL;DR

The paper investigates whether interacting dark energy with a dark matter–dark energy coupling can resolve the $H_0$ tension between Planck CMB constraints and Riess 2016 measurements. By modeling a coupling $Q = \xi \mathcal{H} \rho_{de}$ (with $\xi<0$ for stability) and exploring a freely varying equation of state $w$, the authors analyze Planck data alone and in combination with external datasets (BAO, JLA, WL, lensing, and the Riess $H_0$ prior). They find that a negative coupling shifts $H_0$ upward and reduces the tension with Riess 2016, with evidence strengthening to >2σ when $w$ is fixed, and even pointing toward phantom-like $w<-1$ when the Riess prior is included. However, adding BAO/JLA often mitigates this evidence, returning results closer to LCDM; thus the coupling remains an interesting possibility but not conclusively favored. Overall, the work demonstrates that DM–DE interactions can alleviate cosmological tensions under certain data combinations, motivating further observational tests.

Abstract

The answer is Yes! We indeed find that interacting dark energy can alleviate the current tension on the value of the Hubble constant $H_0$ between the Cosmic Microwave Background anisotropies constraints obtained from the Planck satellite and the recent direct measurements reported by Riess et al. 2016. The combination of these two datasets points towards an evidence for a non-zero dark matter-dark energy coupling $ξ$ at more than two standard deviations, with $ξ=-0.26_{-0.12}^{+0.16}$ at $95\%$ CL. However the $H_0$ tension is better solved when the equation of state of the interacting dark energy component is allowed to freely vary, with a phantom-like equation of state $w=-1.184\pm0.064$ (at $68 \%$ CL), ruling out the pure cosmological constant case, $w=-1$, again at more than two standard deviations. When Planck data are combined with external datasets, as BAO, JLA Supernovae Ia luminosity distances, cosmic shear or lensing data, we find good consistency with the cosmological constant scenario and no compelling evidence for a dark matter-dark energy coupling.

Figures (3)

• Figure 1: $68\%$ and $95\%$ CL in the two-dimensional ($\xi$, $H_0$) planes from the "Planck TT + lowTEB" dataset (left panel) and "Planck TTTEEE + lowTEB" dataset (right panel) also combined with the R16 prior on the Hubble constant. Notice that the presence of a coupling $\xi$ allows for larger values for $H_0$ from Planck data. The inclusion of the R16 prior results in an indication for $\xi<0$ with a significance above two standard deviations.
• Figure 2: Left panel: $68\%$ and $95\%$ CL in the two-dimensional ($\Omega_m$, $\sigma_8$) plane from the "Planck TTTEEE + lowTEB" dataset for a pure $\Lambda$CDM scenario, a varying $\xi$ interacting model, and also adding to the former the WL dataset. Notice that the coupling allows for larger values for $\sigma_8$ and smaller values for $\Omega_m$, relaxing the Planck bounds on the $S_8$ parameter and mildly alleviating the tension with the $S_8$ values measured by cosmic shear surveys as CFHTLenS and KiDS-450. Right panel: $68\%$ and $95\%$ CL in the two-dimensional ($\xi$, $\tau$) plane from the "Planck TTTEEE " dataset, and also combined with the "tau055" prior on the reionization optical depth. Notice that the "tau055" prior affects only marginally the constraints on $\xi$, resulting in a $\sim 1 \sigma$ indication for $\xi<0$ (after marginalization over $\tau$).
• Figure 3: Left panel: $68\%$ and $95\%$ CL in the two-dimensional ($w$, $H_0$) plane from the combination of "Planck TTTEEE + lowTEB" measurements (grey contours), "Planck TTTEEE + lowTEB+ R16" (red contours) and "Planck TTTEEE + lowTEB+ BAO" (blue contours), for an interacting dark matter-dark energy scenario. Right panel: As in the left panel but with $\xi=0$.