A search in gamma-ray burst data for nonconstancy of the velocity of light

The authors discuss possible tests of the constancy of the velocity of light using distant astrophysical sources such as gamma-ray bursters (GRBs), active galactic nuclei (AGNs), and pulsars. This speculative quest may be motivated by some models of quantum fluctuations in the spacetime background, and the authors discuss explicitly how an energy-dependent variation in photon velocity delta c/c~-E/M arises in one particular quantum-gravitational model. They then discuss how data on GRBs may be used to set limits on variations in the velocity of light, which they illustrate using BATSE and OSSE observations of the GRBs that have recently been identified optically and for which precise redshifts are available. They show how a regression analysis can be performed to look for an energy-dependent effect that should correlate with redshift. The present data yield a limit M>or approximately=10/sup 15/ GeV for the quantum gravity scale. They discuss the prospects for improving this analysis using future data, and how one might hope to distinguish any positive signal from astrophysical effects associated with the sources. (47 refs).