Dark energy-dark matter interactions as a solution to the $S_8$ tension

TL;DR

This paper explores a dark energy-dark matter interaction model that can reduce the $S_8$ tension in cosmological data without worsening other tensions or data fits, showing promising results with multiple datasets.

Contribution

It introduces a dynamical dark energy-dark matter coupling model that effectively alleviates the $S_8$ tension while maintaining consistency with various cosmological observations.

Findings

Reduces the significance of the $S_8$ tension in data.

Does not worsen the $H_0$ tension or data fit.

Improves agreement with weak lensing surveys like KiDS and DES.

Abstract

In this work we consider a scenario where the dark energy is a dynamical fluid whose energy density can be transferred to the dark matter via a coupling function proportional to the energy density of the dark energy. In particular, we investigate this model's ability to address the $S_8$ tension and find that against data from Planck, BAO and Pantheon the model 1) can significantly reduce the significance of the tension, 2) does so without exacerbating nor introducing any other tension (such as the $H_0$ tension) and 3) without worsening the fit to the considered data sets with respect to the $\Lambda$CDM model. We also test the model against data from weak lensing surveys such as KiDS and DES, and find that the model's ability to address the $S_8$ tension further improves, without a significant impact on any other parameter nor statistical measure.