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 $\beta -\delta -1\mathrm{/}2=(+0.5\pm 3\pm 0.7)E-10$, a ten-fold improvement compared to the previous best results. We also set a first upper limit for a so far unknown parameter of the Standard Model Extension test theory, $\mathrm{\mid }({\tilde{\kappa }}_{e-}{)}^{ZZ}\mathrm{\mid }<2\cdot E-14$.