2002/04/09 by A. Bauch, S. Weyers · 1 voice · 3 citations
Physics and Astronomy · Decision Sciences · #Advanced Frequency and Time Standards #Scientific Measurement and Uncertainty Evaluation #Radioactive Decay and Measurement Techniques
paper · doi:10.1103/physrevd.65.081101
openalex publication_date 2002/04/09 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
Local position invariance (LPI) is part of the more general Einstein equivalence principle (EEP) which in turn is a foundation of Einstein's theory of general relativity. The EEP predicts a dependence of clock rates on the local gravitational potential U. LPI predicts that the gravitational shift is independent of the atomic species involved as a reference in the clock. It can thus be tested by comparing two different kinds of atomic frequency standard in the same time-varying gravitational potential U(t). In our experiment we made use of the time dependence of U(t) due to Earth's annual elliptical orbital motion. U(t)/c2 varies between \ifmmode±\else\textpm\fi3.3\ifmmode×\else\texttimes\fi10^\ensuremath-10 (c is the speed of light). Comparing a cesium atomic fountain frequency standard with a hydrogen maser for about one year allowed us to set an upper limit on a possible frequency variation of 2.1\ifmmode×\else\texttimes\fi10^\ensuremath-5 of this amount. Compared to previous similar experiments the limit of the notional violation of LPI was reduced by a factor of more than 30.