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Master's Dissertation
DOI
https://doi.org/10.11606/D.14.2020.tde-13052020-230731
Document
Author
Full name
Pedro Eleuterio Mendonça de Almeida
E-mail
Institute/School/College
Knowledge Area
Date of Defense
Published
São Paulo, 2020
Supervisor
Committee
Lima, José Ademir Sales de (President)
Deppman, Airton
Lugones, Germán
Sodre Junior, Laerte
Title in Portuguese
Cosmologias com decaimento do vácuo e K-essência
Keywords in Portuguese
constante cosmológica
cosmologia
decaimento do vácuo
k-essência
Abstract in Portuguese
Nessa dissertação, faremos uma apresentação do modelo padrão da cosmologia, o $\Lambda$CDM. Apresentaremos seu desenvolvimento e as evidências que o apontam como o melhor modelo para descrever o Universo observado até o momento. Em seguida, apresentaremos alguns dos principais problemas dentro desse modelo: o problema da coincidência cosmológica e o problema da constante cosmológica. Com o objetivo de resolver esse problemas, foram propostos vários modelos alternativos na literatura. Nesse trabalho, nos concentraremos em uma classe de modelos com decaimento do vácuo, $\Lambda$(t). Essa classe de modelos possui a vantagem de descrever uma transição exata e suave de uma fase De Sitter primordial instável para a fase da radiação padrão. Esse modelo é não-singular e livre de horizontes. Mostraremos também, como ele é capaz de aliviar os problemas do modelo padrão, mencionados acima. Finalmente, na parte original da dissertação, utilizaremos uma teoria de campos escalares, denominada k-essência, para obter uma descrição de campo escalar do Universo primordial da classe de modelos com decaimento do vácuo. A formulação em termos de campos escalares pode auxiliar no estudo da fase inflacionária desse modelo.
Title in English
Decaying Vacuum Cosmologies and K-essence
Keywords in English
cosmological constant
cosmology
k-essence
vacuum decay
Abstract in English
In this dissertation, we will make a presentation of the standard model of cosmology, the $\Lambda$CDM. We will present its development and the evidence that point it as the best model to describe the Universe observed so far. We will, then, present some of the main problems within this model: the problem of cosmological coincidence and the problem of the cosmological constant. In order to solve these problems, several alternative models have been proposed in the literature. In this work, we will focus on a class of models with vacuum decay, $\Lambda$(t). This model has the advantage of describing an exact and smooth transition from an unstable primordial De Sitter phase to the standard radiation phase. This model is non-singular and free of horizons. We will also show how it is able to alleviate the problems of the standard model, mentioned above. Finally, in the original section of the dissertation, we will use a scalar field theory, dubbed k-essence, to obtain a scalar field description of the vacuum decay model primordial Universe. The formulation in terms of scalar fields can assist in the study of the inflationary phase of this model.
 
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Publishing Date
2020-05-27
 
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