Some models for quantum gravity (QG) violate Lorentz invariance and predict an energy dependence of the speed of light, leading to a dispersion of high-energy gamma-ray signals that travel over cosmological distances. Limits on the dispersion from short-duration substructures observed in gamma-rays emitted by gamma-ray bursts (GRBs) at cosmological distances have provided interesting bounds on Lorentz invariance violation (LIV). Recent observations of unprecedentedly fast flares in the very-high energy gamma-ray emission of the active galactic nuclei (AGNs) Mkn 501 in 2005 and PKS 2155-304 in 2006 resulted in the most constraining limits on LIV from light-travel observations, approaching the Planck mass scale, at which QG effects are assumed to become important. I review the current status of LIV searches using GRBs and AGN flare events, and discuss limitations of light-travel time analyses and prospects for future instruments in the gamma-ray domain.
@article{arxiv.0901.2932,
title = {Exploring Quantum Gravity with Very-High-Energy Gamma-Ray Instruments - Prospects and Limitations},
author = {Robert Wagner},
journal= {arXiv preprint arXiv:0901.2932},
year = {2009}
}
Comments
11 pages, 4 figures, proceedings of "Science with the New Generation of High Energy Gamma-Ray Experiments", Euganean Spa Area, Padova: October 8-10, 2008