Cosmological constraints on multi-interacting dark matter

The increasingly significant tensions within Lambda CDM, combined with the lack of detection of dark matter (DM) in laboratory experiments, have boosted interest in nonminimal dark sectors, which are theoretically well-motivated and inspire new search strategies for DM. Here we consider, for the first time, the possibility of DM having simultaneous interactions with photons, baryons, and dark radiation (DR). We have developed a new and efficient version of the Boltzmann code CLASS that allows for one DM species to have multiple interaction channels. With this framework we reassess existing cosmological bounds on the various interaction coefficients in multi-interacting DM scenarios. We find no clear degeneracies between these different interactions and show that their cosmological effects are largely additive. We further investigate the possibility of these models to alleviate the cosmological tensions, and find that the combination of DM-photon and DM-DR interactions can at the same time reduce the S-8 tension (from 2.3 sigma to 1.2 sigma) and the H-0 tension (from 4.3 sigma to 3.1 sigma). The public release of our code will pave the way for the study of various rich dark sectors.

Automated summary

Researchers explored the possibility of dark matter interacting simultaneously with photons, baryons, and dark radiation, using a new version of the Boltzmann code to reassess cosmological bounds in multi-interacting dark matter scenarios. Their study found that the combination of dark matter-photon and dark matter-DR interactions could potentially alleviate cosmological tensions.