2015/07/31 by Julien Lesgourgues, Gustavo Marques-Tavares, Martin Schmaltz
Physics and Astronomy · #Cold dark matter #Cosmic microwave background #Cosmological perturbation theory #Cosmology and Gravitation Theories #Dark Matter and Cosmic Phenomena #Dark energy #Dark fluid #Dark matter #Particle physics theoretical and experimental studies #Planck #Scalar field dark matter #Warm dark matter #astro-ph.CO #hep-ph
paper · pdf · doi:10.1088/1475-7516/2016/02/037
22 pages, 6 figures; v2 small correction to example models, added acknowledgement; v3 updated likelihoods and changed allowed range for N_fluid, conclusions unchanged. Matches version accepted for publication in JCAP
openalex publication_date 2016/02/16 · arxiv created 2016/03/10 · arxiv updated 2016/03/14 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
We study a two-parameter extension of the cosmological standard model ΛCDM in which cold dark matter interacts with a new form of dark radiation. The two parameters correspond to the energy density in the dark radiation fluid Δ N fluid and the interaction strength between dark matter and dark radiation. The interactions give rise to a very weak ``dark matter drag'' which damps the growth of matter density perturbations throughout radiation domination, allowing to reconcile the tension between predictions of large scale structure from the CMB and direct measurements of σ 8 . We perform a precision fit to Planck CMB data, BAO, large scale structure, and direct measurements of the expansion rate of the universe today. Our model lowers the χ-squared relative to ΛCDM by about 12, corresponding to a preference for non-zero dark matter drag by more than 3σ. Particle physics models which naturally produce a dark matter drag of the required form include the recently proposed non-Abelian dark matter model in which the dark radiation corresponds to massless dark gluons.