Search for features due to a reduction in the inflaton’s speed of sound in the CMB

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 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...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

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Search for features due to a reduction in the inflaton’s speed of sound in the CMB