A recent experiment by Antonini et. al. [Phys. Rev. A {\bf 71}, 050101R
2005], set new limits on Lorentz violating parameters in the frame-work of the
photon sector of the Standard Model Extension (SME),
Îș~eâZZâ, and the Robertson-Mansouri-Sexl (RMS) framework,
ÎČâÎŽâ1/2. The experiment had significant systematic effects caused by
the rotation of the apparatus which were only partly analysed and taken into
account. We show that this is insufficient to put a bound on
Îș~eâZZâ and the bound on ÎČâÎŽâ1/2 represents a
five-fold improvement not a ten-fold improvement as claimed.
(For reply see Phys. Rev. A 72, 066102 (2005) DOI:
10.1103/PhysRevA.72.066102)Comment: 2 page