# Can interacting dark energy solve the $H_0$ tension?

## TL;DR

Interacting dark energy models can potentially resolve the Hubble constant tension between CMB and local measurements, especially when allowing for a phantom-like equation of state, but current combined data favor the cosmological constant.

## Contribution

This study demonstrates that interacting dark energy with a non-zero coupling and a variable equation of state can alleviate the H_0 tension, providing new insights into dark energy dynamics.

## Key findings

- Evidence for non-zero dark matter-dark energy coupling at >2 sigma
- Better H_0 tension resolution with a phantom-like dark energy equation of state
- No strong evidence for dark matter-dark energy interaction when combining multiple datasets

## Abstract

The answer is Yes! We indeed find that interacting dark energy can alleviate the current tension on the value of the Hubble constant $H_0$ between the Cosmic Microwave Background anisotropies constraints obtained from the Planck satellite and the recent direct measurements reported by Riess et al. 2016. The combination of these two datasets points towards an evidence for a non-zero dark matter-dark energy coupling $\xi$ at more than two standard deviations, with $\xi=-0.26_{-0.12}^{+0.16}$ at $95\%$ CL. However the $H_0$ tension is better solved when the equation of state of the interacting dark energy component is allowed to freely vary, with a phantom-like equation of state $w=-1.184\pm0.064$ (at $68 \%$ CL), ruling out the pure cosmological constant case, $w=-1$, again at more than two standard deviations. When Planck data are combined with external datasets, as BAO, JLA Supernovae Ia luminosity distances, cosmic shear or lensing data, we find good consistency with the cosmological constant scenario and no compelling evidence for a dark matter-dark energy coupling.