Towards a Realistic Model of Dark Atoms to Resolve the Hubble Tension

Abstract

It has recently been shown that a subdominant hidden sector of atomic dark matter in the early universe provides a novel avenue towards resolving the Hubble ($H_0$) tension while maintaining good agreement with Cosmic Microwave Background era observables. However, such a mechanism requires a hidden sector whose energy density ratios are the same as in our sector and whose recombination also takes place at redshift $z\approx 1100$, which presents an apparent fine tuning. We introduce a realistic model of this scenario that dynamically enforces these coincidences without fine tuning. In our setup, the hidden sector contains an identical copy of Standard Model (SM) fields, but has a smaller Higgs vacuum expectation value (VEV) and a lower temperature. The baryon asymmetries and reheating temperatures in both sectors arise from the decays of an Affleck-Dine scalar field, whose branching ratios automatically ensure that the reheating temperature in each sector is proportional to the corresponding Higgs VEV. The same setup also naturally ensures that the Hydrogen binding energy in each sector is proportional to the corresponding VEV, so the ratios of binding energy to temperature are approximately equal in the two sectors. Furthermore, our scenario predicts a correlation between the SM/hidden temperature ratio and the atomic dark matter abundance and automatically yields values for these quantities favored by concordant early- and late-universe measurements of $H_0$.

6 pages, 2 figures. Clarifications and a new figure. Matches published version

References in corpus (6)

• In the Realm of the Hubble tension $-$ a Review of Solutions
• Cosmic Distances Calibrated to 1% Precision with Gaia EDR3 Parallaxes and Hubble Space Telescope Photometry of 75 Milky Way Cepheids Confirm Tension with LambdaCDM
• Measurements of the Hubble Constant: Tensions in Perspective
• Dark Nuclei I: Cosmology and Indirect Detection
• Affleck-Dine inflation
• Cosmological Production of Dark Nuclei

Cited by in corpus (8)

• On the evolution of the Hubble constant with the SNe Ia Pantheon Sample and Baryon Acoustic Oscillations: a feasibility study for GRB-cosmology in 2030
• Scaling Transformations and the Origins of Light Relics Constraints from Cosmic Microwave Background Observations
• Dark Black Holes in the Mass Gap
• Thomson scattering: One rate to rule them all
• Impact of gravitational waveform model systematics on the measurement of the Hubble constant
• Dark Matter-Radiation Scattering Enhances CMB Phase Shift through Dark Matter-loading
• EDGES of the dark forest: A new absorption window into the composite dark matter and large scale structure
• Dark Acoustic Oscillations as an Early-Universe Explanation of the DESI Anomaly