Comment on “Test of constancy of speed of light with rotating cryogenic optical resonators”

A recent experiment by Antonini et al. [Phys. Rev. A 71, 050101 (2005)] set new limits on Lorentz violating parameters in the framework of the photon sector of the standard model extension, ${\tilde{\kappa }}_{e-}^{ZZ}$, and the Robertson–Mansouri–Sexl framework, $\beta -\delta -1∕2$. The experiment had significant systematic effects caused by the rotation of the apparatus which was only partly analyzed and taken into account. We show that this is insufficient to put a bound on ${\tilde{\kappa }}_{e-}^{ZZ}$, and that the bound on $\beta -\delta -1∕2$ represents a fivefold, not tenfold, improvement as claimed.