Primordial non-Gaussianities: Theory and Prospects for Observations

• Ano de defesa: 2018
• Autor(a) principal: Guandalin, Caroline Macedo
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: eng
• Instituição de defesa: Biblioteca Digitais de Teses e Dissertações da USP
• Palavras-chave em Português: Bispectro; Bispectrum; Cosmological Perturbation Theory; Espectro de Potências; Estrutura em Larga Escala; Galaxy Surveys; Inflação; Inflation; Large-Scale Structure; Levantamentos de Galáxias; Multi-Tracer Technique; Não-Gaussianidades Primordiais; Power-spectrum; Primordial Non-Gaussianities; Primordial Universe; Técnica de Múltiplos Traçadores; Teoria de Perturbações Cosmológica; Universo Primordial
• Link de acesso: http://www.teses.usp.br/teses/disponiveis/43/43134/tde-24092018-155602/

Early Universe physics leaves distinct imprints on the Cosmic Microwave Background (CMB) and Large-Scale Structure (LSS). The current cosmological paradigm to explain the origin of the structures we see in the Universe today (CMB and LSS), named Inflation, says that the Universe went through a period of accelerated expansion. Density fluctuations that eventually have grown into the temperature fluctuations of the CMB and the galaxies and other structures we see in the LSS come from the quantization of the scalar field (inflaton) which provokes the accelerated expansion. The most simple inflationary model, which contains only one slowly-rolling scalar field with canonical kinetic term in the action, produces a power-spectrum (Fourier transform of the two-point correlation function) approximately scale invariant and an almost null bispectrum (Fourier transform of the three-point correlation function). This characteristic is called Gaussianity, once random fields that follow a normal distribution have all the odd moments null. Yet, more complex inflationary models (with more scalar fields and/or non-trivial kinetic terms in the action, etc) and possible alternatives to inflation have a non-vanishing bispectrum which can be parametrized by a non-linearity parameter f_NL, whose value differs from model to model. In this work we studied the basic ingredients to understand such statements and focused on the observational evidences of this parameters and how the current and upcoming galaxy surveys are able to impose constraints to the value of f_NL with a better accuracy, through the multi-tracer technique, than those obtained by means of CMB measurements.