High Energy Astrophysics Tests of Lorentz Invariance Violation
  Multi-TeV spectra of Mkn 501 and other BL Lac objects exhibit the high energy cutoffs predicted to be the result of intergalactic annihilation interactions, primarily with IR photons having the flux level determined by various astrophysical observations. After correcting for such intergalactic absorption, these spectra can be explained within the framework of synchrotron self-Compton emission models. Stecker and Glashow have shown that the existence of this annihilation via electron-positron pair production puts strong constriants on Lorentz invariance violation. Such constriants have important implications for some quantum gravity and large extra dimension models. A much smaller amount of Lorentz invariance violation has potential implications for understanding the spectra of ultrahigh energy cosmic rays. 
F.W. Stecker (NASA/GSFC)