@inproceedings{339b6af34e0349d8857515bd339a67f2,
title = "Improved limits on variation of the fine structure constant and violation of Local Position Invariance",
abstract = "We report tests of Local Position Invariance (LPI) and constancy of fundamental constants from measurements of the frequency ratio of the 282-nm 199Hg+ optical clock transition to the ground-state hyperfine splitting in 133Cs. Analysis of the frequency ratio, extending over six years at NIST, is used to place a limit on the fractional variation of the two clocks of less than 5.8 × 10-6 per change in normalized solar gravitational potential, and a limit on fractional variation of the fine structure constant at < 1.3 × 10-165 yr -1, assuming invariance of other fundamental constants. Comparison of our results with those previously reported for the absolute optical frequency measurements of 171Yb+ versus other 133Cs standard yields a coupled constraint of -0.04 × 10-15 < ᾱ/α < 0.46 × 10-15 yr-1 and -2.39 × 10-15 < ᾱ/α < 0.47 × l0-15 yr-1.",
author = "Fortier, {T. M.} and N. Ashby and Bergquist, {J. C.} and Delaney, {M. J.} and Diddams, {S. A.} and Heavner, {T. P.} and L. Hollberg and Itano, {W. M.} and Jefferts, {S. R.} and K. Kim and Oskay, {W. H.} and Parker, {T. E.} and J. Shirley and Stalnaker, {J. E.} and F. Levi and L. Lorini",
year = "2007",
doi = "10.1109/FREQ.2007.4319157",
language = "English",
isbn = "1424406463",
series = "Proceedings of the IEEE International Frequency Control Symposium and Exposition",
pages = "663--665",
booktitle = "2007 IEEE International Frequency Control Symposium Joint with the 21st European Frequency and Time Forum, FCS",
note = "2007 IEEE International Frequency Control Symposium Joint with the 21st European Frequency and Time Forum, FCS ; Conference date: 29-05-2007 Through 01-06-2007",
}