New constraints on coupled dark energy from the Planck satellite experiment

Abstract

We present new constraints on coupled dark energy from the recent measurements of the cosmic microwave background anisotropies from the Planck satellite mission. We found that a coupled dark energy model is fully compatible with the Planck measurements, deriving a weak bound on the dark matter--dark energy coupling parameter $\ensuremath{\xi}=\ensuremath{-}{0.49}_{\ensuremath{-}0.31}^{+0.19}$ at 68% C.L. Moreover if Planck data are fitted to a coupled dark energy scenario, the constraint on the Hubble constant is relaxed to ${H}_{0}={72.1}_{\ensuremath{-}2.3}^{+3.2}\text{ }\text{ }\mathrm{km}/\mathrm{s}/\mathrm{Mpc}$, solving the tension with the Hubble Space Telescope (HST) value. We show that a combined $\mathrm{\text{PLANCK}}+\mathrm{HST}$ analysis provides significant evidence for coupled dark energy finding a nonzero value for the coupling parameter $\ensuremath{\xi}$, with $\ensuremath{-}0.90<\ensuremath{\xi}<\ensuremath{-}0.22$ at 95% C.L. We also consider the combined constraints from the Planck data plus the baryon acoustic oscillation measurements of the 6dF Galaxy Survey, the Sloan Digital Sky Survey and the Baron Oscillation Spectroscopic Survey.