Constraining Lorentz violation with cosmology.
Phys Rev Lett 101:26 (2008) 261102
Abstract:
The Einstein-aether theory provides a simple, dynamical mechanism for breaking Lorentz invariance. It does so within a generally covariant context and may emerge from quantum effects in more fundamental theories. The theory leads to a preferred frame and can have distinct experimental signatures. In this Letter, we perform a comprehensive study of the cosmological effects of the Einstein-aether theory and use observational data to constrain it. Allied to previously determined consistency and experimental constraints, we find that an Einstein-aether universe can fit experimental data over a wide range of its parameter space, but requires a specific rescaling of the other cosmological densities.Eddington-Born-Infeld gravity and the large scale structure of the Universe
(2008)
Eddington-Born-Infeld gravity and the large scale structure of the Universe
ArXiv 0811.1272 (2008)
Abstract:
It has been argued that a Universe governed by Eddington-Born-Infeld gravity can be compatible with current cosmological constraints. The extra fields introduced in this theory can behave both as dark matter and dark energy, unifying the dark sector in one coherent framework. We show the various roles the extra fields can play in the expansion of the Universe and study the evolution of linear perturbations in the various regimes. We find that, as a unified theory of the dark sector, Eddington-Born-Infeld gravity will lead to excessive fluctuations in the Cosmic Microwave Background on large scales. In the presence of a cosmological constant, however, the extra fields can behave as a form of non-particulate dark matter and can lead to a cosmology which is entirely compatible with current observations of large scale structure. We discuss the interpretation of this form of dark matter and how it can differ from standard, particulate dark matter.Living in a void: testing the Copernican principle with distant supernovae.
Phys Rev Lett 101:13 (2008) 131302
Abstract:
We show that the local redshift dependence of the luminosity distance can be used to test the Copernican principle that we are not in a central or otherwise special region of the Universe. Future surveys of type Ia supernovae that focus on a redshift range of approximately 0.1-0.4 will be ideally suited to observationally determine the validity of the Copernican principle on new scales, as well as probing the degree to which dark energy must be considered a necessary ingredient in the Universe.The Câ„“over experiment
Proceedings of SPIE the International Society for Optical Engineering 7020 (2008)