The CTA Sensitivity to Lorentz-Violating Effects on the Gamma-Ray   Horizon
  The arrival of TeV-energy photons from distant galaxies is expected to be affected by their QED interaction with intergalactic radiation fields through electron-positron pair production. In theories where high-energy photons violate Lorentz symmetry, the kinematics of the process $\gamma + \gamma\rightarrow e^+ + e^-$ is altered and the cross-section suppressed. Consequently, one would expect more of the highest-energy photons to arrive if QED is modified by Lorentz violation than if it is not. We estimate the sensitivity of Cherenkov Telescope Array (CTA) to changes in the $\gamma$-ray horizon of the Universe due to Lorentz violation, and find that it should be competitive with other leading constraints. 
Malcolm Fairbairn, Albin Nilsson, John Ellis, Jim Hinton, Richard   White
astro-ph.HE astro-ph.CO gr-qc hep-ph