Tests of Lorentz Invariance Using a Microwave Resonator: An Update

TL;DR

This study improves constraints on Lorentz invariance violations by comparing cryogenic sapphire oscillator and hydrogen maser frequencies, updating previous limits through enhanced experimental data and analysis.

Contribution

It provides new, more stringent bounds on Lorentz invariance violation parameters using microwave resonator tests, with significant methodological and data analysis improvements.

Findings

Constraints on Lorentz violation parameters improved by a factor of 2.

New bounds on Mansouri and Sexl test theory parameters established.

Experimental setup and data analysis enhancements contributed to the improved limits.

Abstract

The frequencies of a cryogenic sapphire oscillator and a hydrogen maser are compared to set new constraints on a possible violation of Lorentz invariance. We determine the variation of the oscillator frequency as a function of its orientation (Michelson-Morley test) and of its velocity (Kennedy-Thorndike test) with respect to a preferred frame candidate. We constrain the corresponding parameters of the Mansouri and Sexl test theory to $\delta - \beta + 1/2 \leq 3.4 \times 10^{-9}$ and $\beta - \alpha - 1 \leq 4.1 \times 10^{-7}$ which is of the same order as the best previous result for the former and represents a 50 fold improvement for the latter. These results correspond to an improvement of our previously published limits [Wolf P. et al., Phys. Rev. Lett. {\bf 90}, 6, 060402, (2003)] by about a factor 2. We describe the changes of the experiment, and show the new data that lead to that improvement.