Planck-scale Lorentz-symmetry test theories
Abstract
Description
In the recent quantum-gravity literature there has been strong interest in the possibility of Planck-scale departures from Lorentz symmetry, including possible modifications of the energy/momentum dispersion relation. I stress that a meaningful characterization of the progress of experimental bounds on these Planck-scale effects requires the analysis of some reference test theories, and I propose to focus on two ``minimal'' test theories, a pure-kinematics test theory and an effective-field-theory-based test theory. I illustrate some features of the phenomenology based on these test theories considering some popular strategies for constraining Planck-scale effects, and in particular I observe that sensitivities that are already in the Planck-scale range for some parameters of the two test theories can be achieved using observations of TeV photons from Blazars, both using the so-called ``gamma-ray time-of-flight analyses'' and using the now robust evidence of absorption of TeV photons. Instead the Crab-nebula synchrotron-radiation analyses, whose preliminary sensitivity estimates raised high hopes, actually do not lead to any bound on the parameters of the two ``minimal'' test theories. The Crab-nebula synchrotron-radiation analyses do however constrain some possible generalizations of one of the minimal test theories. As an example of forthcoming data which could provide extremely stringent (beyond-Planckian) limits on the two minimal test theories I consider the possibility of studies of the GZK cutoff for cosmic-rays.
shorter version to comply with page limits of proceedings volume (to appear in proceedings of Huntsville Workshop 2002)
shorter version to comply with page limits of proceedings volume (to appear in proceedings of Huntsville Workshop 2002)