Testing the foundations of special relativity using cryogenic optical resonators

Summary form only given. The special theory of relativity lies at the very foundation of today´s understanding of physics. As a consequence all physical laws have to be Lorentz-covariant. However, recent proposals to formulate a consistent quantum theory of gravity predict modified Maxwell equations´ that are not necessarily Lorentz covariant. Therefore it is important to perform improved optical tests of Lorentz covariance. Michelson-Morley (MM) experiments test the isotropy of the speed of light, /spl Delta/c/sub /spl theta///c, whereas Kennedy-Thorndike (KT) experiments test the dependence of c on the laboratory speed, /spl Delta/c/sub v//c. KT-experiments can be viewed as a comparison between a time standard and a length standard. Both types of tests can be performed using high-finesse optical resonators and, in the case of KT experiments, an additional independent optical frequency standard. Here we discuss the prospect of improved MM and KT tests with an at least 10-fold improvement of sensitivity.