Search for Lorentz Violation in a Short-range Gravity Experiment

Local Lorentz invariance is at the foundation of both the Standard Model of particle physics and General Relativity, but is generally poorly tested for the latter theory. Violation of Lorentz symmetry would break the isotropy of spacetime, permitting the vacuum to fill with ‘background’ fields that have a preferred direction. Interaction of the test masses in a terrestrial gravity experiment with these fields could result in a sidereal modulation of the force between the masses, thus providing a test of Lorentz invariance in gravity. A quantitative description of Lorentz violation consistent with local field theory is given by the Standard-Model Extension (SME), which has recently been expanded to include gravitational effects. The expression for the potential between two test masses m1 and m2 in the ‘pure gravity’ sector of the SME is given by: