Comparação do comportamento termodinâmico de um modelo confinante de quarks com outros modelos efetivos da QCD

• Autor(a) principal: Cerqueira, Matheus Costa
• Data de Publicação: 2017
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: Biblioteca Digital de Teses e Dissertações da UERJ
• Texto Completo: http://www.bdtd.uerj.br/handle/1/16574
• topic: Quantum chromodynamics; Quantum field theory; Nuclear models; Effective models for QCD; Finite temperature quantum field theory; Positivity Violation in QFT; Cromodinâmica quântica; Quarks; Teoria quântica de campos; Modelos nucleares; Modelos efetivos para a QCD; Teoria quântica de campos a temperatura finita; Violação de positividade em TQC; CIENCIAS EXATAS E DA TERRA::FISICA::FISICA DAS PARTICULAS ELEMENTARES E CAMPOS::TEORIA GERAL DE PARTICULAS E CAMPOS

In this Master thesis, we describe some nonperturbative models for Quantum Chromodynamics (QCD), in order to explore the infrared region of the strong nuclear force. In particular, we focus on the thermodynamics of the chiral Quark-Meson (QM) and Polyakov-Quark-Meson (QPM) models, besides the Hadron Resonance Gas (HRG), as these are well established models. Besides these models, we deal with a nonlocal quark model which displays positivity violation and is a candidate for a description of the phenomenon of confinement in QCD. A way to investigate this nonlocal quark model is by studying its thermodynamical behavior. Thus, one can compare the thermodynamical variables in this model with those of the other models previously mentioned, in order to understand how a model with positivity violation behaves compared to the others. We made a description using the formalism of Finite Temperature Quantum Field Theory, with the intent of describing the partition function of such models and therefore find the thermodyamical functions of interest. Our results show thermodynamical instabilities at low temperatures, which we argue that may be related to positivity violation of the quark propagator within the model (which is compatible with results from lattice QCD). Therefore, we believe that there may always be thermodynamical instabilities in any attempt of a microscopic description which has confined degrees of freedom as a starting point.