Lorentz Violation and Ultrahigh-Energy Photons

TL;DR

This paper investigates how potential Lorentz invariance violations could alter the behavior of ultra-high-energy photons, electrons, and positrons, and uses cosmic ray observations to constrain these violations.

Contribution

It generalizes existing constraints on Lorentz violation parameters for photons, electrons, and positrons, considering first and second order Planck-scale suppressed modifications.

Findings

Current non-observation constrains Lorentz violation parameters.

Detection of ultra-high-energy photons would extend these constraints.

The study provides a framework for future experimental bounds.

Abstract

The propagation of photons, electrons and positrons at ultra-high energies above 10^{19} eV can be changed considerably if the dispersion relations of these particles are modified by terms suppressed by powers of the Planck scale. We recently pointed out that the current non-observation of photons in the ultra-high energy cosmic ray flux at such energies can put strong constraints on such modified dispersion relations. In the present work we generalize these constraints to all three Lorentz invariance breaking parameters that can occur in the dispersion relations for photons, electrons and positrons at first and second order suppression with the Planck scale. We also show how the excluded regions in these three-dimensional parameter ranges would be extended if ultra-high energy photons were detected in the future.