Consistency test of the fine-structure constant from the whole ionization history

TL;DR

This study tests the consistency of the fine-structure constant across the entire ionization history of the universe, revealing a significant discrepancy between the recombination and reionization epochs based on current data.

Contribution

It extends previous constraints by including the reionization epoch in the analysis of the fine-structure constant, highlighting potential issues in data calibration.

Findings

Constraint during recombination: α_rec/α_EM ≈ 1.0015

Constraint during reionization: α_rei/α_EM ≈ 0.854

Discrepancy between epochs at 4.64σ significance

Abstract

In cosmology, the fine-structure constant can affect the whole ionization history. However, the previous works confine themselves to the recombination epoch and give various strong constraints on the fine-structure constant. In this paper, we also take the reionization epoch into consideration and do a consistency test of the fine-structure constant from the whole ionization history. From the data combination of Planck 2018, BAO data, SNIa samples, SFR density from UV and IR measurements, and the $Q_\text{HII}$ constraints, we find the constraint on the fine-structure constant during the recombination epoch is $\alpha_{\text{rec}}/\alpha_{\text{EM}}=1.001494^{+0.002041}_{-0.002063}$ and its counterpart during the reionization epoch is $\alpha_{\text{rei}}/\alpha_{\text{EM}}=0.854034^{+0.031678}_{-0.027209}$ at 68$\%$ C.L.. They are not consistent with each other by $4.64\sigma$. A conservative explanation for such a discrepancy is that there are some issues in the data we used. We prefer a calibration of some important parameters involved in reconstructing the reionization history.