The Hubble Constant in the Axi-Higgs Universe

Understand

The $\Lambda$CDM model provides an excellent fit to the CMB data.

• However, a statistically significant tension emerges when its determination of the Hubble constant $H_0$ 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 $\Lambda$CDM model.
• It relaxes the $H_0$ tension as well as explains the $^7$Li puzzle in Big-Bang nucleosynthesis, the clustering $S_8$ tension with the weak-lensing data, and the observed isotropic cosmic birefringence in CMB.