Hubble constant in the axi-Higgs universe

Abstract

The Λ-cold-dark-matter (ΛCDM) model provides an excellent fit to the cosmic microwave background (CMB) data. However, a statistically significant tension emerges when its determination of the Hubble constant H0 is compared to the local distance-redshift measurements. The axi-Higgs model, which couples an ultralight axion to the Higgs field, offers a specific variation of the ΛCDM model. It relaxes the H0 tension as well as explains the Li7 puzzle in big bang nucleosynthesis, the clustering S8 tension with the weak-lensing (WL) data, and the observed isotropic cosmic birefringence in CMB. In this Letter, we demonstrate how the H0 and S8 tensions can be relaxed simultaneously, by correlating the axion impacts on the early and late universe. In a benchmark scenario (m=2×10-30 eV) selected for upcoming experimental tests, the analysis combining the CMB+BAO (baryon acoustic oscillation)+WL+SN data yields H0=69.9±1.5 km/s/Mpc and S8=0.8045±0.0096. Combining this [excluding the SN (supernovae) part] with the local distance-redshift measurements yields H0=72.42±0.76 km/s/Mpc, while S8 is slightly more suppressed.