Galaxy clusters, type Ia supernovae and the fine structure constant

TL;DR

This paper investigates how measurements of galaxy clusters and supernovae can be used to constrain possible variations in the fine structure constant over cosmic time, finding no significant evidence for such variation.

Contribution

It demonstrates that the Sunyaev-Zeldovich and X-ray technique depends on the fine structure constant and derives constraints on its variation using current observational data.

Findings

No significant variation of the fine structure constant detected.

Current data are consistent with a constant $eta$ over the observed redshift range.

Method links galaxy cluster measurements with supernova data to test fundamental physics.

Abstract

As is well known, measurements of the Sunyaev-Zeldovich effect can be combined with observations of the X-ray surface brightness of galaxy clusters to estimate the angular diameter distance to these structures. In this paper, we show that this technique depends on the fine structure constant, $\alpha$. Therefore, if $\alpha$ is a time-dependent quantity, e.g., $\alpha=\alpha_0 \phi(z)$, where $\phi$ is a function of redshift, we argue that current data do not provide the real angular diameter distance, $D_{\rm{A}}(z)$, to the cluster but instead $D_A^{data}(z) = \phi(z)^2 D_{\rm{A}}(z)$. We use this result to derive constraints on a possible variation of $\alpha$ for a class of dilaton runaway models considering a sample of 25 measurements of $D_A^{data}(z)$ in redshift range $0.023 < z < 0.784$ and estimates of $D_{\rm{A}}(z)$ from current type Ia supernovae observations. We find no significant indication of variation of $\alpha$ with the present data.