The signature of the scattering between dark sectors in large scale cosmic microwave background anisotropies

TL;DR

This paper investigates how elastic scattering between dark matter and dark energy affects cosmic microwave background anisotropies, providing constraints on the scattering cross section for certain dark energy equations of state.

Contribution

It introduces a novel analogy between dark sector scattering and Thomson scattering, deriving constraints on dark matter-dark energy elastic scattering from CMB data.

Findings

Tight constraints on scattering cross section for $w<-1$

No meaningful constraints for $w=-1$

Derived upper limit of $\sigma_D < 3.295 imes 10^{-10} \sigma_T$ for proton-mass dark matter

Abstract

We study the interaction between dark sectors by considering the momentum transfer caused by the dark matter scattering elastically within the dark energy fluid. Describing the dark scattering analogy to the Thomson scattering which couples baryons and photons, we examine the impact of the dark scattering in CMB observations. Performing global fitting with the latest observational data, we find that for a dark energy equation of state $w<-1$, the CMB gives tight constraints on dark matter-dark energy elastic scattering. Assuming a dark matter particle of proton mass, we derive an elastic scattering cross section of $\sigma_D < 3.295 \times 10^{-10} \sigma_T$ where $\sigma_T$ is the cross section of Thomson scattering. For $w>-1$, however, the constraints are poor. For $w=-1$, $\sigma_D$ can formally take any value.