Scattering of Dark Matter and Dark Energy

TL;DR

This paper explores the possibility that dark matter and dark energy can have a significant elastic scattering cross-section without disrupting the standard cosmological observations, suggesting a weak impact on structure growth.

Contribution

It introduces a model where dark matter and dark energy interact via elastic scattering with large cross-sections, without altering background cosmology.

Findings

Dark matter-dark energy scattering cross-section can be much larger than Thomson cross-section.

The growth of large-scale structure is only weakly suppressed by this interaction.

The background cosmology remains consistent with observations despite the scattering.

Abstract

We demonstrate how the two dominant constituents of the Universe, dark energy and dark matter, could possess a large scattering cross-section without considerably impacting observations. Unlike models involving energy exchange between the two fluids, the background cosmology remains unaltered, leaving fewer observational signatures. Following a brief review of the scattering cross-sections between cosmologically significant particles, we explore the implications of an elastic interaction between dark matter and dark energy. The growth of large scale structure is suppressed, yet this effect is found to be weak due to the persistently low dark energy density. Thus we conclude that the dark matter-dark energy cross section may exceed the Thomson cross-section by several orders of magnitude.