| Various models for quantum gravity such as string theory, loop quantum gravity, or spacetime foam, have allowed for the possibility that Lorentz symmetry is not an exact symmetry. Instead, Lorentz symmetry is a low energy symmetry that is violated strongly near the Planck energy of approximately 1019 GeV. This work examines various conceptual and technical issues that arise in the construction of Lorentz symmetry violating effective field theories compatible with gravitation and general covariance. The ramifications in a cosmological framework of one such construction, that where Lorentz symmetry is violated by a dynamical preferred frame, are then discussed. As well, this dissertation derives significant observational constraints on Lorentz symmetry violation from astrophysical processes. These constraints rule out Lorentz symmetry violation suppressed by a single power of the Planck energy as has been suggested by some current proposals for quantum gravity. |
