# Dark sectors with dynamical coupling

## TL;DR

This paper investigates models where dark matter and dark energy interact with a time-dependent coupling parameter, using recent cosmological data to constrain these scenarios and assess their viability.

## Contribution

It introduces and constrains the most general coupled dark sector models with a dynamical coupling parameter using current observational data.

## Key findings

- CMB data favors a positive coupling parameter, reducing dark matter.
- Dynamical coupling models alleviate some cosmological tensions.
- Bayesian evidence shows no strong preference for dynamical coupling.

## Abstract

Coupled dark matter-dark energy scenarios are modeled via a dimensionless parameter $\xi$, which controls the strength of their interaction. While this coupling is commonly assumed to be constant, there is no underlying physical law or symmetry that forbids a time-dependent $\xi$ parameter. The most general and complete interacting scenarios between the two dark sectors should therefore allow for such a possibility, and it is the main purpose of this study to constrain two possible and well-motivated coupled cosmologies by means of the most recent and accurate early and late-time universe observations. We find that CMB data alone prefers $\xi(z) >0$ and therefore a smaller amount of dark matter, alleviating some crucial and well-known cosmological data tensions. An objective assessment of the Bayesian evidence for the coupled models explored here shows no particular preference for the presence of a dynamical dark sector coupling.