Probes of Lorentz Violation
  Lorentz invariance is such an important principle of fundamental physics that
it should constantly be subjected to experimental scrutiny as well as
theoretical questioning. Distant astrophysical sources of energetic photons
with rapid time variations, such as active galactic nuclei (AGNs) and gamma-ray
bursters (GRBs), provide ideal experimental opportunities for testing Lorentz
invariance. The Cherenkov Telescope Array (CTA) is an excellent experimental
tool for making such tests with sensitivities exceeding those possible using
other detectors.
