Effects of Lorentz symmetry violation in cosmological models

Abstract

Lorentz symmetry is a fundamental symmetry in nature. It plays an important role in both particle physics in microscopic quantum scale and gravitation theories in macroscopic scale. However, this symmetry is expected to be broken at the Planck scale as the effect suggested from quantum gravity. It is possible that some consequent effects of Lorentz violation can be found in the low-energy effective field theories. Investigations on the Lorentz violation effects gain a lot of attention over the past ten years and many approaches to study these effects have been developed. The Lorentz violation effects in cosmological models are provided by the existence of the æther field. In this thesis, an investigation of the æther field effects is divided into two parts, time-like and space-like æther field. For the time-like æther field, the constraints for the æther parameters are imposed by several experiments. The æther parameters are also constrained by the stability of the models. The effects of the viable time-like æther field in inflationary models are reviewed. The dynamics of inflation is slightly modified and the primordial perturbations are significantly changed. For the effects of space-like æther field on the cosmological models, we consider the Maxwell-like æther field in the Casimir dark energy models in 5-dimensional spacetime. In the Casimir dark energy models, the mechanism for stabilizing the extra dimension are destroyed when non-relativistic matter is taken into account. It is found that the æther field can reduce the effective force acting on the radion field. The radion field will be slowed down before it passes the minimum of the potential. Therefore, the radion field can settle down at the minimum of the potential and the stability is restored.