Quantifying the $S_8$ tension and evidence for interacting dark energy from redshift-space distortion measurements

TL;DR

This paper examines how redshift-space distortion measurements can constrain interactions between dark energy and dark matter, potentially resolving the $S_8$ tension in cosmology.

Contribution

It introduces a comprehensive analysis of dark sector interactions using RSD data combined with other cosmological observations, providing new bounds on the interaction parameter.

Findings

RSD data impose strong upper bounds on dark sector interactions.

Models with positive coupling $\xi$ can alleviate the $S_8$ tension.

Combined data constrains the strength and sign of dark energy-dark matter interactions.

Abstract

In recent years, Cosmic Microwave Background (CMB) observations, Weak Lensing surveys, and $f\sigma_8(z)$ measurements from Redshift-Space Distortions (RSD) have revealed a significant ($\sim$3$-$5$\sigma$) discrepancy in the inferred value of the matter clustering parameter $S_8$. In this work, we investigate the implications of RSD for a cosmological framework postulating an interaction between Dark Energy (DE) and Dark Matter (DM). We explore scenarios where DM can transfer energy-momentum to DE or vice versa. The energy-momentum flow is characterized by the strength and the sign of the coupling parameter $\xi$. Our baseline analysis combines RSD measurements with the latest data from Baryon Acoustic Oscillations (BAO) observed by DESI, Type Ia Supernovae from the PantheonPlus sample, and CMB data from Planck. We demonstrate that RSD measurements provide significant additional information imposing new and strong upper bounds on possible interaction in the dark sector. Models with $\xi > 0$ can effectively alleviate the tension in $S_8$, presenting them as compelling alternatives.