Tests of local position invariance using continuously running atomic clocks

摘要

Tests of local position invariance (LPI) made by comparing the relativeredshift of atomic clocks based on different atoms have been carried out for avariety of pairs of atomic species. In most cases, several absolute frequencymeasurements per year are used to look for an annual signal, resulting in teststhat can span on order of a decade. By using the output of continuously runningclocks, we carry out LPI tests with comparable or higher precision after lessthan 1.5 years. These include new measurements of the difference in redshiftanomalies \beta\ for hyperfine transitions in Rb87 and Cs133 and in H and Cs133and a measurement comparing Rb87 and H, resulting in a stringent limit on LPI,\beta(Rb) - \beta(H)=(-2.7 +/- 4.9) x 10^(-7). The method of making thesemeasurements for continuous clocks is discussed.