Constraining photon dispersion relations from observations of the Vela pulsar with H.E.S.S

Understand

Some approaches to Quantum Gravity (QG) predict a modification of photon dispersion relations due to a breaking of Lorentz invariance.

• The effect is expected to affect photons near an effective QG energy scale.
• This scale has been constrained by observing gamma rays emitted from variable astrophysical sources such as gamma-ray bursts and flaring active galactic nuclei.
• Pulsars exhibit a periodic emission of possibly ms time scale.