Axi-Higgs cosmology
Leo W. H. Fung, Lingfeng Li, Tao Liu, Hoang Nhan Luu, Yu-Cheng Qiu, S.-H. Henry Tye
Abstract
If the electroweak Higgs vacuum expectation value v in early universe is ∼ 1 % higher than its present value v0=246 GeV, the 7Li puzzle in BBN and the CMB/ΛCDM tension with late-universe measurements on Hubble parameter are mitigated. We propose a model of an axion coupled to the Higgs field, named "axi-Higgs", with its mass ma ∼ 10-30 - 10-29 eV and decay constant fa ∼ 1017 - 1018 GeV, to achieve this goal. The axion initial value aini yields an initial Δ vini/v0 ∼ 0.01 throughout the BBN-recombination epoch and a percent level contribution to the total matter density today. Because of its very large de Broglie wavelength, this axion matter density ωa suppresses the matter power spectrum, alleviating the CMB/ΛCDM S8/σ8 tension with the weak-lensing data. It also explains the recently reported isotropic cosmic birefringence by its coupling with photons. Adding the axion (m ∼ 10-22eV) in the fuzzy dark matter model to the axi-Higgs model allows bigger Δ vrec and ωa to address the Hubble and S8/σ8 tensions simultaneously. The model predicts that Δ v may be detected by the spectral measurements of quasars, while its oscillation may be observed in the atomic clock measurements.