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A<sc>bstract</sc> Atomic dark matter is a simple but highly theoretically motivated possibility for an interacting dark sector that could constitute some or all of dark matter. We perform a comprehensive study of precision cosmological observables on minimal atomic dark matter, exploring for the first time the full parameter space of dark QED coupling and dark electron and proton masses (αD,$$ {m}_{e_D} $$ ,$$ {m}_{p_D} $$ ) as well as the two cosmological parameters of aDM mass fractionfDand temperature ratioξat time of SM recombination. We also show how aDM can accommodate the (H0, S8) tension from late-time measurements, leading to a better fit than ΛCDM or ΛCDM + dark radiation. Furthermore, including late-time measurements leads to closed contours of preferredξand dark hydrogen binding energy. The dark proton mass is seemingly unconstrained. Our results serve as an important new jumping-off point for future precision studies of atomic dark matter at non-linear and smaller scales.
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This content will become publicly available on July 1, 2026
Atomic dark matter, interacting dark radiation, and the Hubble tension
A<sc>bstract</sc> We present a new class of interacting dark sector models that can address the Hubble tension. Interacting dark radiation (DR) has previously been put forward as a solution to the problem, but this proposal is disfavored by the high-ℓcosmic microwave background (CMB) data. We modify this basic framework by introducing a subcomponent of dark matter (DM) that interacts strongly with the DR, so that together they constitute a tightly coupled fluid at early times. We show that if this subcomponent decouples from the interacting DR during the CMB epoch, theℓmodes of the CMB that entered the horizon before decoupling are impacted differently from those that entered after, allowing a solution to the problem. We present a model that realizes this framework, which we dub “New Atomic Dark Matter”, or nuADaM, in which the interacting dark matter (iDM) subcomponent is composed of dark atoms, and dark “neutrinos” with long-range interactions contribute to the DR, hence the name of the model. This iDM subcomponent is acoustic at early times but decouples from the DR following dark recombination. In contrast to conventional atomic dark matter (ADM) models, the dark photon is part of a richer DR sector, which ensures that it continues to be self-interacting even after recombination. We show that this model admits a significantly larger value ofH0than ΛCDM when fit to CMB and BAO data, while maintaining a comparable goodness of fit. Once the SHOES data set is included, it provides a significantly better fit than ΛCDM.
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- Award ID(s):
- 2412828
- PAR ID:
- 10624981
- Publisher / Repository:
- Springer Nature
- Date Published:
- Journal Name:
- Journal of High Energy Physics
- Volume:
- 2025
- Issue:
- 7
- ISSN:
- 1029-8479
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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