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The 2009 Fermi Symposium

Constraining Lorentz-Invariance Violation with Fermi

Vlasios Vasileiou, CRESST NASA/GSFC & UMBC


Some quantum-gravity theories allow for the violation of Lorentz invariance, predicting a dependence of a photon's speed on its energy. Because of this dependence, two photons of different energy that were emitted simultaneously from a distant astrophysical source may not arrive the same time at the Earth. The magnitude of the effect depends on the energy scale that quantum-gravity effects become important: the Quantum-Gravity mass (MQG), a mass expected to be near the Planck Mass. We will present lower limits on M_QG, derived from broadband (8keV to >300GeV) observations of GRB090510 and GRB080916c by the GBM and LAT instruments on board the Fermi spacecraft. For the first time, limits on MQG greater than the Planck Mass have been placed, rendering some of the quantum-gravity theories extremely unlike.