Robust Constraint on Lorentz Violation Using Fermi-LAT Gamma-Ray Burst Data

TL;DR

This study uses Fermi-LAT gamma-ray burst data to set constraints on Lorentz violation, finding that any linear energy dependence in photon propagation must occur above a scale of a few times 10^{17} GeV.

Contribution

It introduces a novel statistical approach analyzing burst irregularity, kurtosis, and skewness to constrain Lorentz invariance violation using gamma-ray data.

Findings

Energy scale for Lorentz violation exceeds 10^{17} GeV

Method constrains dispersion effects during photon propagation

Future observations could improve sensitivity

Abstract

Models of quantum gravity suggest that the vacuum should be regarded as a medium with quantum structure that may have non-trivial effects on photon propagation, including the violation of Lorentz invariance. Fermi Large Area Telescope (LAT) observations of gamma-ray bursts (GRBs) are sensitive probes of Lorentz invariance, via studies of energy-dependent timing shifts in their rapidly-varying photon emissions. In this paper we analyze the Fermi-LAT measurements of high-energy gamma rays from GRBs with known redshifts, allowing for the possibility of energy-dependent variations in emission times at the sources as well as a possible non-trivial refractive index in vacuo for photons. We use statistical estimators based on the irregularity, kurtosis and skewness of bursts that are relatively bright in the 100 MeV to multi-GeV energy band to constrain possible dispersion effects during propagation. We find that the energy scale characterizing a linear energy dependence of the refractive index should exceed a few $\times 10^{17}$ GeV, and we estimate the sensitivity attainable with additional future sources to be detected by Fermi-LAT.