Atomic clock comparisons provide some of the most precise tests of Lorentz and CPT symmetries in the laboratory. With data from multiple such experiments using different nuclei, it is possible to constrain new regions of the parameter space for Lorentz violation. Relativistic effects in the nuclei allow us to disentangle forms of Lorentz violation which could not be separately measured in purely nonrelativistic experiments. The disentangled bounds in the neutron sectors are at the ${10}^{-28}\mathrm{GeV}$ level, far better than could be obtained with any other current technique.

• Received 14 January 2009

DOI:https://doi.org/10.1103/PhysRevD.79.061702