Does the Proton-to-Electron Mass Ratio µ = m _p / m _e Vary in the Course of Cosmological Evolution?

Abstract

The possible cosmological variation of the proton-to-electron mass ratio μ = m _p / m _e was estimated by measuring the H₂ wavelengths in the high-resolution spectrum of the quasar Q 0347–382. Our analysis yielded an estimate for the possible deviation of μ, value in the past, 10 Gyr ago: for the unweighted value Δ μ / μ = (3.0 ± 2.4) × 10⁻⁵; for the weighted value

$$ \Delta \mu /\mu = (5.02 \pm 1.82) \times {10^{ - 5}} $$

Since the significance of the both results does not exceed 3σ, further observations are needed to increase the statistical significance. In any case, this result may be considered as the most stringent estimate on an upper limit of a possible variation of μ, (95% C.L.):

$$ \left| {\Delta \mu /\mu } \right| < 8 \times {10^{ - 5}}. $$

This value serves as an effective tool for selection of models determining a relation between possible cosmological deviations of the fine-structure constant α and the elementary particle masses (m _p , m _e , etc.).