TESTS OF LORENTZ INVARIANCE USING HIGH-ENERGY ASTROPHYSICS OBSERVATIONS

High-energy astrophysics observations provide the best possibilities to detect a very small violation of Lorentz invariance, such as may be related to the structure of spacetime near the Planck scale. I will discuss the possible signatures of Lorentz invariance violation that can be manifested by observing the spectra, polarization, and timing of γ-rays from active galactic nuclei and γ-ray bursts. Other sensitive tests are provided by observations of the spectra of ultrahighenergy cosmic rays and very high-energy neutrinos. I will also discuss a new time-of-flight analysis of observations of GRB 090510 by the Fermi γ-ray Space Telescope. These results, based on high-energy astrophysical observations, have fundamental implications for spacetime physics and quantum gravity models.