Test of constancy of speed of light with rotating cryogenic optical resonators

A test of Lorentz invariance for electromagnetic waves was performed by comparing the resonance frequencies of two optical resonators as a function of orientation in space. In terms of the Robertson-Mansouri-Sexl theory, we obtain $\beta -\delta -1∕2=(+0.5\pm 3\pm 0.7)\times {10}^{-10}$, a tenfold improvement compared to the previous best results. We also set a first upper limit for a parameter of the standard model extension test theory, $\mid {\left({\tilde{\kappa }}_{e-}\right)}^{ZZ}\mid <2\times {10}^{-14}$.