Constraints on the Coupling between Dark Energy and Dark Matter from CMB data

TL;DR

This study explores models where dark energy and dark matter interact non-gravitationally, using diverse cosmological data to constrain the models and find that energy transfer from dark energy to dark matter aligns better with observations.

Contribution

It provides the first comprehensive constraints on phenomenological dark sector coupling models using multiple cosmological datasets, highlighting the preference for dark energy feeding dark matter.

Findings

Models with dark energy feeding dark matter fit observational data well.

Dark matter decay into dark energy increases tension with H0 and sigma8 measurements.

Energy transfer from dark energy to dark matter reconciles high- and low-redshift data.

Abstract

We investigate a phenomenological non-gravitational coupling between dark energy and dark matter, where the interaction in the dark sector is parameterized as an energy transfer either from dark matter to dark energy or the opposite. The models are constrained by a whole host of updated cosmological data: cosmic microwave background temperature anisotropies and polarization, high-redshift supernovae, baryon acoustic oscillations, redshift space distortions and gravitational lensing. Both models are found to be compatible with all cosmological observables, but in the case where dark matter decays into dark energy, the tension with the independent determinations of $H_0$ and $\sigma_8$, already present for standard cosmology, increases: this model in fact predicts lower $H_0$ and higher $\sigma_8$, mostly as a consequence of the higher amount of dark matter at early times, leading to a stronger clustering during the evolution. Instead, when dark matter is fed by dark energy, the reconstructed values of $H_0$ and $\sigma_8$ nicely agree with their local determinations, with a full reconciliation between high- and low-redshift observations. A non-zero coupling between dark energy and dark matter, with an energy flow from the former to the latter, appears therefore to be in better agreement with cosmological data.