Limits on variations in fundamental constants from 21-cm and ultraviolet quasar absorption lines
Abstract
Quasar absorption spectra at 21-cm and UV rest-wavelengths are used to estimate the time variation of x=alpha2 gp mu, where alpha is the fine structure constant, gp the proton g factor, and me/mp=mu the electron/proton mass ratio. Over a redshift range 0.24 ~< zabs ~< 2.04, <Delta x/x>totalweighted=(1.17+-1.01) x 10-5. A linear fit gives d/dtx/x=(-1.43+-1.27) x 10-15 yr-1. Two previous results on varying alpha yield the strong limits Delta mu/mu=(2.31+-1.03) x 10-5 and Delta mu/mu=(1.29+-1.01) x 10-5. Our sample, 8x larger than any previous, provides the first direct estimate of the intrinsic 21-cm and UV velocity differences ~6 km s-1.
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