Cosmological evolution of the proton-to-electron mass ratio in an extended Brans-Dicke theory

Abstract

We study variation of the proton-to-electron mass ratio $ \mu=m_{p}/m_{e} $ by incorporating standard model (SM) of particle physics into an extended Brans-Dicke theory. We show that the evolution of the Higgs vacuum expectation value (VEV), with expansion of the Universe, leads to the variation of the proton-to-electron mass ratio. This is because the electron mass is proportional to the Higgs VEV, while the proton mass is mainly dependent on the quantum chromodynamics (QCD) energy scale, i.e., $ \Lambda_{QCD} $. Therefore, using the experimental and cosmological constraints on the variation of the $ \mu $ we can constrain the variation of the Higgs VEV. This study is important in understanding the recent claims of the detection of a variation of the proton-to-electron mass ratio in quasar absorption spectra.