Orientador: Prof. Dr. Germán Lugones / Dissertação (mestrado) - Universidade Federal do ABC, Programa de Pós-Graduação em Física, 2014. / Neste trabalho, estudamos a transicao de fase de materia hadronica a materia quarks em estrelas de neutrons e proto-estrelas de neutrons. A transicao comeca com o deconfinamento dos hadrons, que e governado pelas interacoes fortes, e e seguido pelo decaimento fraco dos quarks ate que a materia de quarks atinge o equilibrio quimico. Calculamos a taxa de todos os processos de interacao fraca relevantes na materia quarks quente e densa e resolvemos a equacao de Boltzmann, a fim de obter a escala de tempo de decaimento e a emissividade de neutrinos. Na equacao de estado, analisamos sistematicamente o efeito das interacoes fortes perturbativamente ate primeira ordem em ¿¿c, e o efeito datemperatura finita e massa do quark estranho. Nossos resultados mostram que a transicao aumenta a temperatura da materia quarks ate 60.70 MeV e o equilibrio quimico e atingido em uma escala de tempo de um nanossegundo. A emissividade de neutrinos por barion e muito grande, o que leva a emissao de uma energia por barion de 10.60 MeV sob a forma de neutrinos. Finalmente, analisamos as consequencias astrofisicas dos resultados. / Thermodynamics allows us to analyze the performance of thermal machines, which has the ability to convert the heat into useful work. Among others, the laws of thermodynamics (especially the second) impose limits in various processes including information processing in classical computers. The development of increasingly smaller computing devices, has raised questions about which would limit the applicability of the laws of thermodynamics, when they are close to the quantum limit. This type of questioning has linked different disciplines into a new area of research that has been called quantum thermodynamics. This dissertation is inserted into this new field of knowledge. Specifically we study the possibility of implementing a quantum heat engine which operates out of equilibrium, and employs a single "qubit" as working substance. For this purpose we use the underlying tools of fluctuations theorems to adequately express quantities such as work and heat (which in the quantum context are stochastic variables). We describe in detail the thermodynamic cycle for work extraction in finite time, whose dynamics is controlled by "quenches", or sudden changes in an external field. The proposed protocol can be implemented and fully characterized using the current technology in the context of " Nuclear Magnetic Resonance (NMR)". Finally, we show the regimes of the machine operation