Non-parametric reconstruction of the fine structure constant with galaxy clusters

TL;DR

This study uses galaxy cluster data and non-parametric methods to investigate potential variations in the fine structure constant over cosmic time, highlighting the influence of different Hubble constant values.

Contribution

It introduces a non-parametric approach combining galaxy cluster observations and supernova data to test for variations in the fine structure constant, considering different $H_0$ values.

Findings

Constant $\alpha$ is excluded at 3$\sigma$ with Planck $H_0$ for $z \\lesssim 0.5$.

Agreement with constant $\alpha$ is restored using local $H_0$ estimates.

The results depend on the choice of the Hubble constant.

Abstract

Testing possible variations in fundamental constants of nature is a crucial endeavor in observational cosmology. This paper investigates potential cosmological variations in the fine structure constant ($\alpha$) through a non-parametric approach, using galaxy cluster observations as the primary cosmological probe. We employ two methodologies based on galaxy cluster gas mass fraction measurements derived from X-ray and Sunyaev-Zeldovich observations, along with luminosity distances from type Ia supernovae. We also explore how different values of the Hubble constant ($H_0$) impact the variation of $\alpha$ across cosmic history. When using the Planck satellite's $H_0$ observations, a constant $\alpha$ is ruled out at approximately the 3$\sigma$ confidence level for $z \lesssim 0.5$. Conversely, employing local estimates of $H_0$ restores agreement with a constant $\alpha$.