Interacting dark energy after the latest Planck, DES, and $H_0$ measurements: an excellent solution to the $H_0$ and cosmic shear tensions.
We examine the most well-studied model featuring non-gravitational interactions between dark matter and dark energy in light of the latest cosmological observations. Our data includes Cosmic Microwave Background (CMB) measurements from the Planck 2018 legacy data release, 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. We find that the presence of interactions among the two dark sectors can bring the significance level of the long-standing $H_0$ tension below the $1\sigma$ level. The very same model also significantly reduces the $\Omega_{\rm m}-\sigma_8$ tension between CMB and cosmic shear measurements. Interactions between the dark components of our Universe remain therefore as an extremely promising solution to these persisting cosmological tensions. The results presented in this paper are among the first constraints on exotic physics from the Planck 2018 legacy dataset. In a companion paper, we will further investigate these tensions when allowing for more freedom in the dark energy sector.