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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 -+1/2= (1. 54. 2) 10^-9 and --1= (-3. 16. 9) 10^-7 which is of the same order as the best previous result for the former and represents a 30-fold improvement for the latter.
Wolf et al. (Wed,) studied this question.