Use of the gravitational-wave interferometers to test Lorentz invariance   violation
  Currently operating gravitational-wave interferometers are Michelson interferometers with effective arm length L ~ 4x10e5 m. While the interferometer remains in lock, data at the fsr sideband frequency encode information on slow phase changes in the f ~ 10e-5 Hz range, with a fringe sensitivity ~ 10e-10. Preliminary LIGO data presented in 2009 show no Lorentz violating signal at the second harmonic of the Earth's sidereal frequency. This sets a limit on a possible change in refractine index, dn/n < 2x10e-22, an improvement of more than three orders of magnitude over existing limits. 
Adrian Melissinos
gr-qc