Primordial hydrogen recombination dynamics with recoil upon scattering in the Ly-α line

We show that including the recoil upon scattering in the Ly-alpha line can lead to a noticeable acceleration of the primordial hydrogen recombination. Thus, for example, for the Lambda CDM model, the decrease in the degree of ionization exceeds 1% at redshifts z = 800-1050, reaching approximate to 1.3% at z = 900. The corresponding corrections to the calculated cosmic microwave background power spectra reach 1.1% and 1.7% for TT and EE spectra, respectively. The radiative transfer in these calculations was treated in the quasi-stationary approximation.We have also obtained numerical solutions (in the diffusion approximation) to the nonstationary problem of radiative transfer in the Ly-alpha line for a partial frequency redistribution with recoil. We trace the evolution of the local line profile and the relative number of uncompensated transitions from the 2p state to the 1s state. We show that including the nonstationarity of the Ly-alpha line radiative transfer can lead to an additional acceleration of the primordial hydrogen recombination.