2004/12/31 by P. Tzanavaris, John K. Webb, J. K. Webb +3 · 2 citations
Physics and Astronomy · #Astrophysics and Cosmic Phenomena #Cosmology and Gravitation Theories #Galaxies: Formation, Evolution, Phenomena #astro-ph #hep-ph #physics.atom-ph
paper · pdf · doi:10.1103/physrevlett.95.041301
published as Phys.Rev.Lett.95:041301,2005 · 12 pages, 9 figures, accepted on 10 June 2005 for publication in Physical Review Letters. Results unchanged. Minor restructuring of abstract and one reference added. Pages 1-4 identical to accepted version following referees' comments. Pages 5-12 show plots to improve understanding of this work
arxiv created 2005/07/11 · openalex publication_date 2005/07/22 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
Quasar absorption spectra at 21-cm and UV rest wavelengths are used to estimate the time variation of x\ensuremath≡\ensuremathα2gp\ensuremathμ, where \ensuremathα is the fine structure constant, gp the proton g factor, and me/mp\ensuremath≡\ensuremathμ the electron/proton mass ratio. Over a redshift range 0.24\ensuremath\lesssimzabs\ensuremath\lesssim2.04, ⟨\ensuremathΔx/x⟩totalweighted=(1.17\ifmmode±\else\textpm\fi1.01)\ifmmode×\else\texttimes\fi10^\ensuremath-5. A linear fit gives \stackrel\ifmmode \else \textperiodcentered \fix/x=(\ensuremath-1.43\ifmmode±\else\textpm\fi1.27)\ifmmode×\else\texttimes\fi10^\ensuremath-15 yr^\ensuremath-1. Two previous results on varying \ensuremathα yield the strong limits \ensuremathΔ\ensuremathμ/\ensuremathμ=(2.31\ifmmode±\else\textpm\fi1.03)\ifmmode×\else\texttimes\fi10^\ensuremath-5 and \ensuremathΔ\ensuremathμ/\ensuremathμ=(1.29\ifmmode±\else\textpm\fi1.01)\ifmmode×\else\texttimes\fi10^\ensuremath-5. Our sample, 8\ifmmode×\else\texttimes\fi larger than any previous, provides the first direct estimate of the intrinsic 21-cm and UV velocity differences \ensuremath∼6 km s^\ensuremath-1.