Limits on variations in fundamental constants from 21-cm and ultraviolet quasar absorption lines
Abstract
21-cm and ultraviolet quasar absorption spectra are used to estimate the time variation of x==alpha^2 g_p mu, where alpha is the fine structure constant, g_p the proton g factor, and m_e/m_p==mu the electron/proton mass ratio. The sample used is 8 times larger than previously used. Systematic errors are estimated for the first time. Over a redshift range ~0.24 < z_abs < ~2.04, _total=(0.35+-1.09) x 10^-5. A linear fit gives dot{x}/x=(-1.30+-1.51) x 10^-15 yr^-1. Using two previous results on varying alpha yields the best limits Delta mu/mu=(1.5+-1.1) x 10^-5 and Delta mu/mu=(0.5+-1.1) x 10^-5.Keywords
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