Fundamental Constants as Monitors of the Universe

TL;DR

Astronomical observations of fundamental constants like the proton-electron mass ratio and fine structure constant provide crucial tests for the invariance of physical laws over cosmic time, impacting theories of new physics and cosmology.

Contribution

This paper quantitatively relates the proton-electron mass ratio to particle physics parameters and discusses new constraints on their possible variation over time.

Findings

Current limits on the proton-electron mass ratio variation are at 1.E-7.

Constraints on the fine structure constant variation are at 1E-5.

Relationships between fundamental constants and particle physics parameters are quantitatively defined.

Abstract

Astronomical observations have a unique ability to determine the laws of physics at distant times in the universe. They, therefore, have particular relevance in answering the basic question as to whether the laws of physics are invariant with time. The dimesionless fundamental constants, such as the proton to electron mass ratio and the fine structure constant are key elements in the investigation. If they vary with time then the answer is clearly that the laws of physics are not invariant with time and significant new physics must be developed to describe the universe. Limits on their variance, on the other hand, constrains the parameter space available to new physics that requires a variation with time of basic physical law. There are now observational constraints on the time variation of the proton to electron mass ratio mu at the 1.E-7 level. Constraints on the variation of the fine structure constant alpha are less rigorous, 1E-5, but are imposed at higher redshift. The implications of these limits on new cosmologies that require rolling scalar fields has already had its first investigations. Here we address the implications on basic particle physics. The proton to electron mass ratio is obviously dependent on the particle physics parameters that set the mass of the proton and the electron. To first order the ratio is dependent on a combination of the Quantum Chromodynamic scale, the Yukawa couplings, and the Higgs Vacuum Expectation Value. Here that relationship is quantitative defined for the first time. When coupled with previous determinations of the relation of the fine structure constant to the same parameters two constraints exist on the fractional variation of these parameters with time. A third independent constraint involving only the three parameters could set the stage for constraints on their individual fractional variation.