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Phys. Rev. Lett. 98, 070802 (2007) [4 pages]

Testing Local Position Invariance with Four Cesium-Fountain Primary Frequency Standards and Four NIST Hydrogen Masers

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N. Ashby
Department of Physics, University of Colorado, Boulder, Colorado 80309-0390, USA

T. P. Heavner, S. R. Jefferts, and T. E. Parker
Time and Frequency Division, National Institute of Standards and Technology, Boulder, Colorado 80305, USA

A. G. Radnaev and Y. O. Dudin
Lebedev Physical Institute, Frequency Standards Laboratory, Moscow, Russia

Received 18 December 2006; published 16 February 2007

We report the most sensitive tests to date of the assumption of local position invariance (LPI) underlying general relativity, based on a 7 yr comparison of cesium and hydrogen atomic clocks (frequency standards). The latest results place an upper limit that is over 20 times smaller than the previous most sensitive tests; this is consistent with the null shift predicted by LPI. The result is based on precise comparisons of frequencies of four hydrogen masers maintained by NIST, with four independent Cs fountain clocks—one at NIST and three in Europe—as the Sun’s gravitational potential at Earth’s surface varies due to Earth’s orbital eccentricity.

© 2007 The American Physical Society

URL:
http://link.aps.org/doi/10.1103/PhysRevLett.98.070802
DOI:
10.1103/PhysRevLett.98.070802
PACS:
06.30.Ft, 04.80.Cc

*Affiliate: National Institute of Standards and Technology, Boulder, CO 80305, USA.

Electronic address: ashby@boulder.nist.gov

See Also

See Also: T. M. Fortier, N. Ashby, J. C. Bergquist, M. J. Delaney, S. A. Diddams, T. P. Heavner, L. Hollberg, W. M. Itano, S. R. Jefferts, K. Kim, F. Levi, L. Lorini, W. H. Oskay, T. E. Parker, J. Shirley, and J. E. Stalnaker, Precision Atomic Spectroscopy for Improved Limits on Variation of the Fine Structure Constant and Local Position Invariance, Phys. Rev. Lett. 98, 070801 (2007).

 
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