Modified hydrogen recombination rate due to non-Hubble redshift effects

Abstract

The accumulation of observational data in recent years has led to a peculiar situation in which measurements of the cosmological parameters made by various collaborations and using different methods yield significantly different values. A solution to this problem may be found by modifying the models used to obtain these values. In this work, we revisit the standard approach to the recombination calculation and investigate a mechanism that can introduce corrections to the rate at which Lyman-alpha photons escape the resonance line. We find that interactions of Lyman-alpha line photons with moving neutral hydrogen atoms can become a source of such a correction. An analysis of CMB data for the modified model favors the existence of a non-Hubble redshift effect and prefers slightly higher values of $H_0$ and smaller values of $Ω_m$ and $S_8$ compared to the standard $Λ$CDM model, as well as a smaller value of the scalar spectrum index $n_s$.