Constraining the time variation of the coupling constants from cosmic microwave background: effect of \Lambda_{QCD}

TL;DR

This paper constrains the possible time variation of fundamental constants like the fine structure constant, electron mass, and proton mass using CMB data, considering their interdependence and forecasting future constraints from PLANCK.

Contribution

It introduces a comprehensive analysis of coupled variations of fundamental constants affecting CMB, including b5, b4b5/b5, and b4b5/b5, with a focus on the QCD scale b4b5bcd.

Findings

95% CL constraint on b5: -8.28e-3 to 1.81e-3

Constraint on b5 ratio: -0.52 to 0.17

Forecasted constraints from PLANCK data

Abstract

We investigate constraints on the time variation of the fine structure constant between the recombination epoch and the present epoch, \Delta\alpha/\alpha \equiv (\alpha_{rec} - \alpha_{now})/\alpha_{now}, from cosmic microwave background (CMB) taking into account simultaneous variation of other physical constants, namely the electron mass m_{e} and the proton mass m_{p}. In other words, we consider the variation of Yukawa coupling and the QCD scale \Lambda_{QCD} in addition to the electromagnetic coupling. We clarify which parameters can be determined from CMB temperature anisotropy in terms of singular value decomposition. Assuming a relation among variations of coupling constants governed by a single scalar field (the dilaton), the 95% confidence level (C.L.) constraint on \Delta\alpha/\alpha is found to be -8.28 \times 10^{-3} < \Delta\alpha/\alpha < 1.81 \times 10^{-3}, which is tighter than the one obtained by considering only the change of \alpha and m_{e}. We also obtain the constraint on the time variation of the proton-to-electron mass ratio \mu \equiv m_{p}/m_{e} to be -0.52 < \Delta\mu/\mu < 0.17 (95% C.L.) under the same assumption. Finally, we also implement a forecast for constraints from the PLANCK survey.