Using ultra-high energy cosmic rays and air showers to test Lorentz invariance within modified Maxwell theory

TL;DR

This paper discusses how ultra-high energy cosmic rays and air showers can be used to test Lorentz invariance, providing new bounds on Lorentz violation parameters in the photon sector.

Contribution

It offers an updated limit on Lorentz violation parameter $$ based on cosmic-ray observations and preliminary results from air shower analyses.

Findings

LV parameter $$ constrained to -0.6e-20 to 6e-20 (98% CL)

No evidence of vacuum Cherenkov radiation observed

Updated bounds improve previous limits on Lorentz violation

Abstract

Cosmic rays and air showers at ultra-high energy are unique tools to test the validity of Lorentz invariance. A brief overview is given on such tests focusing on isotropic, non-birefringent Lorentz violation (LV) in the photon sector. Based on the apparent absence of vacuum Cherenkov radiation and photon decay, the LV parameter $\kappa$ is bound to $-0.6 \cdot 10^{-20} < \kappa < 6 \cdot 10^{-20}$ (98\% CL). We report an updated limit from cosmic-ray photon observations and preliminary results on testing vacuum Cherenkov radiation in air showers.