LIV Laugh Love: Searches for Lorentz invariance violation with ground-based gamma-ray telescopes

Samantha Wong ( Université McGill )

Many attempts to unify the fundamental forces, such as quantum gravity and string theory remain primarily theoretical, due to a lack of expected observational effects. This makes it difficult to test these theories and determine which to pursue further. Fortunately, some theories of quantum gravity predict Lorentz invariance violation (LIV), which would allow an energy-dependent (rather than absolute) speed of light. LIV can be observed in very high energy (VHE; > 100 TeV) photons, which are best found in cosmic accelerators - extreme astrophysical environments such as active galactic nuclei (AGN), gamma-ray bursts (GRBs), and pulsars. Though the expected effects of LIV on photon travel speeds are small, they are expected to accumulate over distance and observation time. I present the efforts of a collaboration between all four major operating ground-based VHE imaging atmospheric Cherenkov gamma-ray telescopes (VERITAS, H.E.S.S, MAGIC, and LST) to combine observations in order to produce the deepest limits to-date on LIV and the quantum gravity energy scale.