Hubble tension as a window on the gravitation of the dark matter sector: Exploration of a family of models

Abstract: A family of simple and minimal extensions of the standard cosmological $\Lambda$CDM model in which dark matter experiences an additional long-range scalar interaction is demonstrated to alleviate the long lasting Hubble-tension while letting primordial nucleosynthesis predictions unaffected and passing by construction all current local tests of general relativity. This article describes their theoretical formulation and their implications for dark matter. Then, it investigates their cosmological signatures, both at the background and perturbation levels. A detailed comparison to astrophysical data is performed to discuss their ability to fit existing data. A thorough discussion of the complementarity of the low- and high-redshift data and on their constraining power highlights how these models improve the predictions of the $\Lambda$CDM model whatever the combination of datasets used and why they can potentially resolve the Hubble tension. Being fully predictive in any environment, they pave the way to a better understanding of gravity in the dark matter sector.