2 00 1 Do the fundamental constants vary in the course of the cosmological evolution ?

Do the fundamental constants vary in the course of the cosmological evolution ? Abstract – We estimate the cosmological variation of the proton-to-electron mass ratio µ = m p /m e by measuring the wavelengths of molecular hydrogen transitions in the early universe. The analysis is performed using high spectral resolution observations (F W HM ≈ 7 km/s) of two damped Lyman-α systems at z abs = 2.3377 and 3.0249 observed along the lines of sight to the quasars Q 1232+082 and Q 0347−382 respectively. The most conservative result of the analysis is a possible variation of µ over the last ∼10 Gyrs, with an amplitude ∆µ/µ = (5.7 ± 3.8) × 10 −5. The result is significant at the 1.5σ level only and should be confirmed by further observations. This is the most stringent estimate of a possible cosmological variation of µ obtained up to now.