title: Indications of a spatial variation of the fine structure constant.
abstract: We previously reported Keck telescope observations suggesting a smaller value of the fine structure constant α at high redshift. New Very Large Telescope (VLT) data, probing a different direction in the Universe, shows an inverse evolution; α increases at high redshift. Although the pattern could be due to as yet undetected systematic effects, with the systematics as presently understood the combined data set fits a spatial dipole, significant at the 4.2 σ level, in the direction right ascension 17.5 ± 0.9 h, declination -58 ± 9 deg. The independent VLT and Keck samples give consistent dipole directions and amplitudes, as do high and low redshift samples. A search for systematics, using observations duplicated at both telescopes, reveals none so far which emulate this result.
authors.affiliation: School of Physics, University of New South Wales, Sydney, New South Wales 2052, Australia.
authors.forename: J K
authors.initials: JK
authors.lastname: Webb
authors.forename: J A
authors.initials: JA
authors.lastname: King
authors.forename: M T
authors.initials: MT
authors.lastname: Murphy
authors.forename: V V
authors.initials: VV
authors.lastname: Flambaum
authors.forename: R F
authors.initials: RF
authors.lastname: Carswell
authors.forename: M B
authors.initials: MB
authors.lastname: Bainbridge