An EIT search for Lorentz violating signals
  A test of Lorentz invariance has been performed using an EIT resonance as a precision frequency discriminator within an Ives-Stilwell like apparatus. We analyse the experiment within the framework of the Standard Model Extension and have made the first direct measurment of the parameter $\kappa_{tr}<1.6\times10^{-5}$. 
J. P. Cotter and B. Varcoe