On the Stability of Fundamental Couplings in the Galaxy

TL;DR

This paper provides updated astrophysical constraints on the stability of the fine-structure constant and proton-to-electron mass ratio within the Galaxy, improving previous bounds and exploring implications for fundamental physics models.

Contribution

It revisits and enhances previous analyses by allowing simultaneous variations of both couplings and combining recent measurements, setting tighter bounds on their stability.

Findings

No evidence for variations of α at 0.4 ppm

No evidence for variations of μ at 0.6 ppm

Bounds improve to 0.1 ppm when using Levshakov's prior

Abstract

Astrophysical tests of the stability of Nature's fundamental couplings are a key probe of the standard paradigms in fundamental physics and cosmology. In this report we discuss updated constraints on the stability of the fine-structure constant $\alpha$ and the proton-to-electron mass ratio $\mu=m_p/m_e$ within the Galaxy. We revisit and improve upon the analysis by Truppe {\it et al.} by allowing for the possibility of simultaneous variations of both couplings and also by combining them with the recent measurements by Levshakov {\it et al.} By considering representative unification scenarios we find no evidence for variations of $\alpha$ at the 0.4 ppm level, and of $\mu$ at the 0.6 ppm level; if one uses the Levshakov bound on $\mu$ as a prior, the$\alpha$ bound is improved to 0.1 ppm. We also highlight how these measurements can constrain (and discriminate among) several fundamental physics paradigms.