The inflationary hypothesis was introduced as a solution to the fine-tuning issue in the initial conditions of the Big Bang theory. In this Master’s research project, we introduce our work in the...Show moreThe inflationary hypothesis was introduced as a solution to the fine-tuning issue in the initial conditions of the Big Bang theory. In this Master’s research project, we introduce our work in the search for features in the Cosmic Microwave Background (CMB) power spectra that could result from reductions in the speed of sound of the inflaton. We study these features in the context of an effective single field theory of a multiple field scenario, due to the fact that a single field inflation approach is favoured by the current cosmological data, especially by the CMB. First, we present a brief review of the current cosmological model, the ΛCDM model, inflation and the possible extensions. Secondly, we review the physics of the CMB, the main theoretical cosmological codes and the needed data analysis tools from the point of view of Bayesian statistics. Finally, we update our current search for features using Planck 2015 temperature and polarization data introducing new parametrizations for the reduction of the speed of sound. In this search, we have recovered only some previous found modes, indicating the dependency of our results with respect to the parametrization we were using. For this reason, we have pointed out the necessity of reconstructing the reduction of the speed of sound, showing some preliminary results when Gaussian Processes are used as the reconstruction technique.Show less
In this thesis, we will present some exact Finslerian solutions to a Finsler Einstein Equation. The first chapter contains an introduction to the main concepts of Finsler geometry. In particular,...Show moreIn this thesis, we will present some exact Finslerian solutions to a Finsler Einstein Equation. The first chapter contains an introduction to the main concepts of Finsler geometry. In particular, the mathematical concepts necessary to develop Finsler General Relativity will be introduced. We will briefly elaborate on properties of pp-waves in General Relativity, followed by a presentation of the main ideas of Very Special Relativity (VSR). VSR assumes a reduced symmetry of nature that is a subgroup of the full Lorentz group. A deformation of VSR symmetries gives rise to a Finsler treatment of spacetime, General Very Special Relativity (GVSR). We will extend GVSR in order to incorporate curved spacetimes. Then, we investigate whether the GVSR versions of VSI metrics (including pp-wave metrics) and AdS metrics in four and five dimensions are solutions to the Finsler Einstein equation proposed by Pfeifer. For the former, this is indeed the case (under certain conditions), but the latter raise the problem of a Finsler generalization of a cosmological constant, which we cannot resolve yet. Finally, we give an overview on experiments that have been proposed to detect (G)VSR deviations from Riemannianity and violations of Lorentz invariance. We conclude with a summary of our results and an outlook on further research.Show less
