Ultrahigh-energy photons from LHAASO as probes of Lorentz symmetry violations

The Large High Altitude Air Shower Observatory (LHAASO) is one of the most sensitive gamma-ray detector arrays currently operating at TeV and PeV energies. Recently the LHAASO experiment detected ultra-high-energy (UHE; E-gamma greater than or similar to 100 TeV) photon emissions up to 1.4 PeV from twelve astrophysical gamma-ray sources. We point out that the detection of cosmic photons at such energies can constrain the photon self-decay motivated by superluminal Lorentz symmetry violation (LV) to a higher level, thus can put strong constraints to certain LV frameworks. Meanwhile, we suggest that the current observation of the PeV-scale photon with LHAASO may provide hints to permit a subluminal type of Lorentz violation in the proximity of the Planckian regime, and may be compatible with the light speed variation at the scale of 3.6 x 10(17) GeV recently suggested from gamma-ray burst (GRB) time delays. We further propose detecting PeV photons coming from extragalactic sources with future experiments, based on LV-induced threshold anomalies of e(+)e(-) pair-production, as a crucial test of subluminal Lorentz violation. We comment that these observations are consistent with a D-brane/string-inspired quantum-gravity framework, the space-time foam model.

Automated summary

The LHAASO experiment detected ultra-high-energy photon emissions from twelve astrophysical gamma-ray sources, providing strong constraints to certain Lorentz symmetry violation frameworks. The observation of PeV-scale photons may hint at subluminal Lorentz violation in the proximity of the Planckian regime, and could be compatible with recent suggestions of light speed variation at the scale of 3.6 x 10(17) GeV from gamma-ray burst time delays. Further experiments detecting PeV photons from extragalactic sources may serve as a crucial test of subluminal Lorentz violation. These observations are consistent with a D-brane/string-inspired quantum-gravity framework, the space-time foam model.