The ΛCDM model provides an excellent fit to the 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 7Li puzzle in Big-Bang nucleosynthesis, the clustering
S8​ tension with the weak-lensing data, and the observed isotropic cosmic
birefringence in CMB. In this paper, 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 experimental tests soon, the analysis combining the CMB+BAO+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.Comment: 15 pages, 11 figures, final version published on PRR Lette