A smoking gun from the power spectrum dipole for elastic interactions in the dark sector

TL;DR

This paper proposes that the dipole of the matter power spectrum can reveal the strength of dark sector elastic interactions, potentially resolving the $\sigma_8$ tension in cosmology.

Contribution

It demonstrates that the interaction parameter in dark sector models can be detected through the matter power spectrum dipole in upcoming surveys.

Findings

The interaction strength affects the matter power spectrum dipole.

Upcoming surveys can measure this dipole to detect dark sector interactions.

The model offers a solution to the $\sigma_8$ tension.

Abstract

Models with pure momentum exchange in the dark sector have been shown to provide a promising scenario to tackle the tension in the clustering inferred from high- and low-redshift probes. A distinctive feature of these models is that only the Euler equation for the dark matter component is modified and the correction is such that the net effect can be associated to an additional friction determined by the interaction rate. In this work, we show that the strength of the interaction parameter needed to resolve the $\sigma_8$ tension could be detected from the dipole of the matter power spectrum that is expected to be measured in upcoming surveys.