Interacting dark energy in the early 2020s: a promising solution to the $H_0$ and cosmic shear tensions
Eleonora Di Valentino, Alessandro Melchiorri, Olga Mena, Sunny Vagnozzi
TL;DR
This work revisits interacting dark energy (IDE) with a DM-DE coupling $Q=\xi{\cal H}\rho_x$ in light of Planck 2018 data, DES 3×2pt, BAO, Pantheon, and the local $H_0$ measurement from HST. By fixing the dark energy equation of state to $w\approx-1$ and allowing $\xi<0$ to ensure stable evolution, the study finds that Planck data alone favor a nonzero coupling and yield $H_0$ around $72.8$, effectively addressing the $H_0$ tension; including the HST prior strengthens this result with $\xi\approx-0.66$ and $H_0\approx74$, accompanied by very strong Bayesian evidence for IDE. However, incorporating late-time data like BAO and Pantheon lowers $H_0$ and weakens the coupling signal, bringing the tension to roughly $2.6$–$3\sigma$ and yielding weaker Bayesian support, while DES helps reconcile Planck and DES in the $\Omega_m$–$\sigma_8$ plane by mitigating the $S_8$ tension. The work highlights that IDE remains a promising joint route to the major cosmological tensions but also emphasizes model-dependence concerns for BAO/SNe constraints and the need for future data (e.g., Euclid, gravitational-wave standard sirens) to robustly test late-time dark-sector interactions.
Abstract
We examine interactions between dark matter and dark energy in light of the latest cosmological observations, focusing on a specific model with coupling proportional to the dark energy density. Our data includes Cosmic Microwave Background (CMB) measurements from the Planck 2018 legacy data release, late-time measurements of the expansion history from Baryon Acoustic Oscillations (BAO) and Supernovae Type Ia (SNeIa), galaxy clustering and cosmic shear measurements from the Dark Energy Survey Year 1 results, and the 2019 local distance ladder measurement of the Hubble constant $H_0$ from the Hubble Space Telescope. Considering Planck data both in combination with BAO or SNeIa data reduces the $H_0$ tension to a level which could possibly be compatible with a statistical fluctuation. The very same model also significantly reduces the $Ω_{\rm m}-σ_8$ tension between CMB and cosmic shear measurements. Interactions between the dark sectors of our Universe remain therefore a promising joint solution to these persisting cosmological tensions.