English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Plus monthly

Global: Zendy Tools annual

Global: Zendy Tools monthly

Global: Zendy Free Plan

We compare the long-term fractional frequency variation of four hydrogenmasers that are part of an ensemble of clocks comprising the National Instituteof Standards and Technology,(NIST), Boulder, timescale with the fractionalfrequencies of primary frequency standards operated by leading metrologylaboratories in the United States, France, Germany, Italy and the UnitedKingdom for a period extending more than 14 years. The measure of the assumedvariation of non-gravitational interaction,(LPI parameter, $\beta$)---withinthe atoms of H and Cs---over time as the earth orbits the sun, has beenconstrained to $\beta=(2.2 \pm 2.5)\times 10^{-7}$, a factor of two improvementover previous estimates. Using our results together with the previous bestestimates of $\beta$ based on Rb vs. Cs, and Rb vs. H comparisons, we imposethe most stringent limits to date on the dimensionless coupling constants thatrelate the variation of fundamental constants such as the fine-structureconstant and the scaled quark mass with strong(QCD) interaction to thevariation in the local gravitational potential. For any metric theory ofgravity $\beta=0$.

A null test of General Relativity: New limits on Local Position Invariance and the variation of fundamental constants