http://arxiv.org/abs/0904.3184
**Search for Lorentz Invariance Violation effects with PKS 2155-304 flaring period in 2006 by H.E.S.S**
Authors: J. Bolmont, R. Buehler, A. Jacholkowska, S. J. Wagner, for the H.E.S.S. Collaboration

(Submitted on 21 Apr 2009)

Abstract: Highly energetic, variable and distant sources such as Active Galactic Nuclei provide a good opportunity to evaluate effects due to the emission and the propagation of high energy photons. In this note, a study of possible energy-dependent time-lags with PKS 2155-304 light curve as measured by H.E.S.S. in July 2006 is presented. These time-lags could either come from the emission processes or also sign a Lorentz Symmetry breaking as predicted in some Quantum Gravity models. A Cross-Correlation function and a Wavelet Transform were used to measure the time-lags. The 95% Confidence Limit on the Quantum Gravity energy scale based on the statistical and systematic error evaluation was found to be 7x10^17 GeV considering a linear correction in the standard photon dispersion relations and assuming that emission-induced time-lags are negligible. For now, this limit is the best ever obtained with a blazar.