Exploring Quantum Gravity with Very-High-Energy Gamma-Ray Instruments - Prospects and Limitations

TL;DR

This paper reviews the use of very-high-energy gamma-ray observations from gamma-ray bursts and active galactic nuclei to test quantum gravity theories, discussing current limits and future prospects for detecting Lorentz invariance violation.

Contribution

It provides a comprehensive review of current LIV constraints from gamma-ray observations and discusses the limitations and future potential of gamma-ray instruments in quantum gravity research.

Findings

Fast gamma-ray flares set the most stringent LIV limits to date.

Current observations approach the Planck scale sensitivity.

Future instruments could improve LIV detection prospects.

Abstract

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.