Dark sector interaction: a remedy of the tensions between CMB and LSS data

Abstract

The well-known tensions on the cosmological parameters $H_0$ and $\ddot{I}{ƒ}_8$ within the $\hat{I}›$CDM cosmology shown by the Planck-CMB and LSS data are possibly due to the systematics in the data or our ignorance of some new physics beyond the $\hat{I}›$CDM model. In this letter, we focus on the second possibility, and investigate a minimal extension of the $\hat{I}›$CDM model by allowing a coupling between its dark sector components (dark energy and dark matter). We analyze this scenario with Planck-CMB, KiDS and HST data, and find that the $H_0$ and $\ddot{I}{ƒ}_8$ tensions disappear at 68\% CL. In the joint analyzes with Planck, HST and KiDS data, we find non-zero coupling in the dark sector up to 99\% CL. Thus, we find a strong statistical support from the observational data for an interaction in the dark sector of the Universe while solving the $H_0$ and $\ddot{I}{ƒ}_8$ tensions simultaneously.

5 pages, 3 figures