Tests of relativity using a microwave resonator

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 δ−β+1/2 = (1.5±4.2)×10−9 and β−α−1 = (−3.1±6.9)×10−7 which is equivalent to the best previous result for the former and repre-sents a 30 fold improvement for the latter. PACS number(s): 03.30.+p, 06.30.Ft The Einstein equivalence principle (EEP) is at the heart of special and gen-eral relativity [1] and a cornerstone of modern physics. One of the constituent elements of EEP is Local Lorentz invariance (LLI) which, loosely stated, pos-tulates that the outcome of any local test experiment is independent of th