Beyond the standard cosmology : anisotropic inflation and baryophilic dark matter

摘要

This thesis discusses two topics in cosmology that resulted in two independent publications. The first topic concerns persistent anisotropy during inflation and the second topic concerns a model of baryophillic dark matter. ududThe motivation for the project contained within chapter one came from indications in the cosmic microwave background data that seemed to suggest that there may be a cosmologically preferred direction. Moira Gresham and I derived quantitative predictions about the signals one would observe in Cosmic Microwave Background data if isotropy is not assumed during inflation. We considered a particular example of a dynamical theory of anisotropic inflation that is characterized by a scalar field which is nonminimally coupled to an isotropy breaking abelian gauge field, thereby slowing the decay of the gauge field energy density.ududThe motivation for the project contained within chapter two came from the observation that the global symmetries B (baryon number) and L (lepton number) of the standard model Lagrangian must be broken by higher-dimensional operators at a very high scale. Pavel F. Perez, Mark B. Wise and I analyzed a model that explained the protection of these accidental global symmetries by promoting B and L to gauge symmetries. This model has a natural dark matter, candidate and we discuss the experimental constraints on the parameters in the theory. ududUnexpected results are found in each chapter. For example, in chapter two, we find that the anisotropic contribution to the tensor power spectrum is suppressed with respect to that of the scalar power spectrum and, in chapter three, we show that a baryon asymmetry can be generated even within a model that has baryon number as a gauge symmetry.