Future limits on isotropic Lorentz violation in the photon sector from UHECRs and TeV gamma rays

TL;DR

This paper discusses how current and upcoming cosmic-ray and gamma-ray observatories can set stringent limits on isotropic Lorentz violation in photon physics, potentially reaching sensitivities of 10^{-21}.

Contribution

It introduces a method to use astrophysical observations to constrain Lorentz-violating parameters more tightly than laboratory experiments.

Findings

Future bounds could reach 10^{-21} for Lorentz violation.

Comparison with laboratory bounds shows astrophysical methods are more sensitive.

Implications for fundamental physics are significant at these bounds.

Abstract

Present and future ultra-high-energy-cosmic-ray facilities (e.g., the Pierre Auger Observatory with South and North components) and TeV-gamma-ray telescope arrays (e.g., HESS or VERITAS and CTA) have the potential to set stringent indirect bounds on the nine Lorentz-violating parameters of nonbirefringent modified Maxwell theory minimally coupled to standard Dirac theory. Theoretically, the most interesting case is isotropic Lorentz violation, which is described by a single parameter [taken to vanish for the standard Lorentz-invariant theory]. It appears possible to obtain in the future an upper (lower) indirect bound on this single isotropic Lorentz-violating parameter at the +10^{-21} (-10^{-17}) level. Comparison is made with existing and future direct bounds from laboratory experiments. The possible physics implications of upper bounds at the 10^{-21} level are discussed.