Paper detail

Polarizations of CMB and the Hubble tension

Future precision measurements of CMB polarizations can shed new light on the problem so called Hubble tension. The Hubble tension comes from the difference of the evolutions of the Hubble parameter which are determined with two different distance ladders. The standard distance ladder with the observation of Cepheid variables and type Ia supernovae gives larger values of the Hubble constant, and the inverse distance ladder with the observation of the baryon acoustic oscillations both in the CMB and in the clustering of galaxies gives smaller values of the Hubble constant. These different evolutions of the Hubble parameter indicate different evolutions of the free electron density in the process of the reionization of the universe and different magnitudes of low-l polarizations of the CMB, since these polarizations are mainly produced through the Thomson scattering of CMB photons off these free electrons. We investigate the effect on CMB E-mode and B-mode polarizations of l < 12 assuming non-trivially time-dependent equation of state of dark energy. We find that the case of the standard distance ladder gives higher power of polarizations than the prediction in the LambdaCDM model.