Constraining Lorentz Violation with Fermi

Abstract

One of the cornerstones of special relativity is the postulate that all observers measure exactly the same photon speeds independently on the photon energies. However, a hypothesized structure of spacetime may alter this conclusion at ultra-small length scales. Even a tiny energy-dependent variation in the speed of light may be revealed, when accumulated over cosmological light-travel times, by high temporal-resolution measurements of sharp features in Gamma-Ray Burst lightcurves. We report the results of a study of the emission from GRB 090510 as detected by Fermi's LAT and GBM instruments that set unprecedented limits on the dependence of the speed of light on its energy.