3 Astrophysical constraints on hypothetical variability of fundamental constants

Many-multiplet (MM) method [1] applied to three inhomogeneous samples of Keck/HIRES quasar absorption spectra gives a shift in the value of the fine-structure constant of ∆α/α = (−5.4± 1.2)× 10−6 in the redshift range 0.2 < z < 3.7 [2]. The 1 σ error claimed in [2] is, however, much too small and cannot be maintained by current observations of quasars. We present a modified MM method to set an upper limit on ∆α/α from a homogeneous sample of Fe ii lines identified in the up-to-date best quality VLT/UVES spectrum of HE 0515–4414. Our result is ∆α/α = (1.1±1.1)×10−5 at z = 1.149. Theoretical models of the fundamental physical interactions predict that the protonto-electron mass ratio (μ = mp/me) may relate to the shift in ∆α/α as ∆μ/μ = R∆α/α. We use VLT/UVES high-resolution observations of molecular hydrogen H2 ultraviolet absorption lines at z = 3.025 toward Q 0347–3818 to bound the value of R. The obtained constraints on ∆ ln μ = (2.1±3.6)×10−5 and on ∆ ln α = (1.1±1.1)×10−5 rule out vary large values of |R| > 6. Future observations with a new High Accuracy Radial velocity Planet Searcher (HARPS) spectrograph may provide a crucial test for the ∆α/α measurements at a level of 10−6.