# Constraining the photon’s dispersion relation

**Date:**

Non-standard physics, such as Lorentz Invariance Violation in Quantum Gravity (models or a non-zero photon mass, can lead to an energy-dependent propagation speed for photons, such that photons of different energies from a distant source would arrive at different times, even if they were emitted simultaneously. The short durations and large distances to high energy astrophysical transients therefore allow us to test the fundamental assumptions of the standard models of cosmology and particles physics by considering the energy-dependent time delay between photon arrival time (spectral lag) of Gamma Ray Bursts (GRBs). Many previous attempts to do place constraints on such theories are obtained using a handful of GRBs, do not propagate uncertainties in the redshifts of sources, or suffer from uncertain systematics in the model for other contributions to the spectral lag (noise). In this talk I will discuss recent work in which we looked to overcome these challenges and hence were able to constrain the quantum gravity energy scale and photon mass by constructing probabilistic source-by-source forward models of the time delays for a large sample of GRBs and we demonstrate that these constraints are robust to the choice of noise model.

- Given at:
- Center for Computational Astrophysics, Flatiron Institute (Oct. 2021)
- Battcock Institute/Kavli Institute for Cosmology, University of Cambridge (Oct. 2021)