Setor escuro do universo: uma análise termodinâmica

• Autor(a) principal: Silva, Heydson Henrique Brito da
• Data de Publicação: 2014
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: Repositório Institucional da UFRN
• Texto Completo: https://repositorio.ufrn.br/jspui/handle/123456789/16627
• topic: Energia escura. Matéria escura. Termodinâmica; Dark energy. Dark matter. Thermodynamics; CNPQ::CIENCIAS EXATAS E DA TERRA::FISICA

Significant observational effort has been directed to unveiling the nature of the so-called dark energy. However, given the large number of theoretical possibilities, it is possible that this a task cannot be based only on observational data. In this thesis we investigate the dark energy via a thermodynamics approach, i.e., we discuss some thermodynamic properties of this energy component assuming a general time-dependent equation-of-state (EoS) parameter w(a) = w0 + waf(a), where w0 and wa are constants and f(a) may assume different forms. We show that very restrictive bounds can be placed on the w0 - wa space when current observational data are combined with the thermodynamic constraints derived. Moreover, we include a non-zero chemical potential &#956; and a varying EoS parameter of the type &#969;(a) = &#969;0 + F(a), therefore more general, in this thermodynamical description. We derive generalized expressions for the entropy density and chemical potential, noting that the dark energy temperature T and &#956; evolve in the same way in the course of the cosmic expansion. The positiveness of entropy S is used to impose thermodynamic bounds on the EoS parameter &#969;(a). In particular, we find that a phantom-like behavior &#969;(a) < &#8722;1 is allowed only when the chemical potential is a negative quantity (&#956; < 0). Thermodynamically speaking, a complete treatment has been proposed, when we address the interaction between matter and energy dark