| Abstract: | Atomic dark matter provides a minimal but richly structured extension of the cold dark matter paradigm, featuring self-interactions, gauge symmetries, dark radiation, and the formation of bound states. Such models have gained renewed interest for their potential to ease several tensions in ΛCDM, including small-scale structure anomalies and the H₀ and S₈ discrepancies.
In this talk, I explore a motivated class of high-energy models in which the dark constituents carry a small electric millicharge, allowing interactions between the dark and visible sectors. I will outline the resulting phenomenology and discuss how to test this scenario with CMB data. Some regions of parameter space remain weakly constrained by the CMB, but could leave notable imprints on late-time cosmology, that can be probed with upcoming 21-cm observations. |