Multiple Dark Matter as a self-regulating mechanism for dark sector interactions

TL;DR

This paper explores a model with two dark matter particles having opposite couplings to dark energy, which can produce observable long-range forces in the dark sector without conflicting with current cosmological data.

Contribution

It introduces a two-particle dark matter model with opposite couplings to dark energy, demonstrating its viability and potential for new long-range interactions in the dark sector.

Findings

Dark sector interactions can be strong without conflicting with observations

Two dark matter particles with opposite couplings can produce scalar forces

The model extends previous single-species dark matter scenarios

Abstract

(Abridged) Present cosmological constraints and the absence of a direct detection and identification of any dark matter particle candidate leave room to the possibility that the dark sector of the Universe be actually more complex than it is normally assumed. In particular, more than one new fundamental particle could be responsible for the observed dark matter density in the Universe, and possible new interactions between dark energy and dark matter might characterize the dark sector. In the present work, we investigate the possibility that two dark matter particles exist in nature, with identical physical properties except for the sign of their coupling constant to dark energy. Extending previous works on similar scenarios, we study the evolution of the background cosmology as well as the growth of linear density perturbations for a wide range of parameters of such model. Interestingly, our results show how the simple assumption that dark matter particles carry a "charge" with respect to their interaction with the dark energy field allows for new long-range scalar forces of gravitational strength in the dark sector without conflicting with present observations both at the background and linear levels. Our scenario does not introduce new parameters with respect to the case of a single dark matter species for which such strong dark interactions have been already ruled out.