4 resultados para Classical Theories of Gravity

em Universidade Federal do Rio Grande do Norte(UFRN)


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Since the 1970s, the world observes the fragmentation, hybridity, plurality and miscegenation that are taking over the scenic arts. The contemporary poetry feels free of the classical rules; theater no longer obeys the requirements of the poetic "manuals"; the rigid boundaries between genres disappears; artists cease to represent to the public to talk with him. In the last decades of twentieth century and in the twenty-first century, emerges the laughable phenomenon of One-man Show in the brazilian scene, object of this research, as a result of this evolution of the performing arts. It is a form of theater that emerged in the brazilian context, snatching public attention in alternative spaces, theaters and, as it should be, also on the Internet, often confused with the Stand-up Comedy. It is necessary a research that delimitate and pursue to identify the essential characteristics of the brazilian One- Man Show, not only by the absence of theoretical references concerning this, but also to understand some aspects of the brazilian scene and the situation of laughter and comedy in it. In the first chapter, a discussion about comedy and laughter in classical antiquity is presented, using the writings of Plato and Aristotle as a starting point; in the second, some of the main classical theories of laughter are reviewed, attempting to identify the general characteristics that enable to understand the construction of the comedy; the third chapter generally dicusses about the moment of the brazilian theatrical scene in which emerges the One-man Show; and in the fourth chapter, there is an explanation about this phenomenon and a description of the practical exercise titled Experimento One-person Show: Damas

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The study physical process that control the stellar evolution is strength influenced by several stellar parameters, like as rotational velocity, convective envelope mass deepening, and magnetic field intensity. In this study we analyzed the interconnection of some stellar parameters, as Lithium abundance A(Li), chromospheric activity and magnetic field intensity as well as the variation of these parameters as a function of age, rotational velocity, and the convective envelope mass deepening for a selected sample of solar analogs and twins stars. In particular, we analyzed the convective envelope mass deepening and the dispersion of lithium abundance for these stars. We also studied the evolution of rotation in subgiants stars, because its belong to the following evolutionary stage of solar analogs, and twins stars. For this analyze, we compute evolutionary models with the TGEC code to derive the evolutionary stage, as well as the convective envelope mass deepening, and derive more precisely the stellar mass, and age for this 118 stars. Our Investigation shows a considerable dispersion of lithium abundance for the solar analogs stars. We also realize that this dispersion is not by the convective zone deep, in this way we observed which the scattering of A(Li) can not be explained by classical theories of mixing in the convective zone. In conclusion we have that are necessary extra-mixing process to explain this decrease of Lithium abundance in solar analogs and twins stars. We analyzed the subgiant stars because this are the subsequent evolutionary stage after the solar analogs and twins stars. For this analysis, we compute the rotational period for 30 subgiants stars observed by Co- RoT satellite. For this task we apply two different methods: Lomb-Scargle algorithm, and the Plavchan Periodogram. We apply the TGEC code we compute models with internal distribution of angular momentum to confront the predict results with the models, and the observational results. With this analyze, we showed which solid body rotation models are incompatible with the physical interpretation of observational results. As a result of our study we still concluded that the magnetic field, convective envelope mass deepening, and internal redistribution of angular momentum are essential to explain the evolution of low-mass stars, and its observational characteristics. Based on population synthesis simulation, we concluded that the solar neighborhood presents a considerable quantity of solar twins when compared with the discovered set nowadays. Altogether we foresee the existence around 400 solar analogs in the solar neighborhood (distance of 100 pc). We also study the angular momentum of solar analogs and twins, in this study we concluded that added angular momentum from a Jupiter type planet, putted in the Jupiter position, is not enough to explain the angular momentum predicted by Kraft law (Kraft 1970)

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In this dissertation, after a brief review on the Einstein s General Relativity Theory and its application to the Friedmann-Lemaitre-Robertson-Walker (FLRW) cosmological models, we present and discuss the alternative theories of gravity dubbed f(R) gravity. These theories come about when one substitute in the Einstein-Hilbert action the Ricci curvature R by some well behaved nonlinear function f(R). They provide an alternative way to explain the current cosmic acceleration with no need of invoking neither a dark energy component, nor the existence of extra spatial dimensions. In dealing with f(R) gravity, two different variational approaches may be followed, namely the metric and the Palatini formalisms, which lead to very different equations of motion. We briefly describe the metric formalism and then concentrate on the Palatini variational approach to the gravity action. We make a systematic and detailed derivation of the field equations for Palatini f(R) gravity, which generalize the Einsteins equations of General Relativity, and obtain also the generalized Friedmann equations, which can be used for cosmological tests. As an example, using recent compilations of type Ia Supernovae observations, we show how the f(R) = R − fi/Rn class of gravity theories explain the recent observed acceleration of the universe by placing reasonable constraints on the free parameters fi and n. We also examine the question as to whether Palatini f(R) gravity theories permit space-times in which causality, a fundamental issue in any physical theory [22], is violated. As is well known, in General Relativity there are solutions to the viii field equations that have causal anomalies in the form of closed time-like curves, the renowned Gödel model being the best known example of such a solution. Here we show that every perfect-fluid Gödel-type solution of Palatini f(R) gravity with density and pressure p that satisfy the weak energy condition + p 0 is necessarily isometric to the Gödel geometry, demonstrating, therefore, that these theories present causal anomalies in the form of closed time-like curves. This result extends a theorem on Gödel-type models to the framework of Palatini f(R) gravity theory. We derive an expression for a critical radius rc (beyond which causality is violated) for an arbitrary Palatini f(R) theory. The expression makes apparent that the violation of causality depends on the form of f(R) and on the matter content components. We concretely examine the Gödel-type perfect-fluid solutions in the f(R) = R−fi/Rn class of Palatini gravity theories, and show that for positive matter density and for fi and n in the range permitted by the observations, these theories do not admit the Gödel geometry as a perfect-fluid solution of its field equations. In this sense, f(R) gravity theory remedies the causal pathology in the form of closed timelike curves which is allowed in General Relativity. We also examine the violation of causality of Gödel-type by considering a single scalar field as the matter content. For this source, we show that Palatini f(R) gravity gives rise to a unique Gödeltype solution with no violation of causality. Finally, we show that by combining a perfect fluid plus a scalar field as sources of Gödel-type geometries, we obtain both solutions in the form of closed time-like curves, as well as solutions with no violation of causality

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Since the 1970s, the world observes the fragmentation, hybridity, plurality and miscegenation that are taking over the scenic arts. The contemporary poetry feels free of the classical rules; theater no longer obeys the requirements of the poetic "manuals"; the rigid boundaries between genres disappears; artists cease to represent to the public to talk with him. In the last decades of twentieth century and in the twenty-first century, emerges the laughable phenomenon of One-man Show in the brazilian scene, object of this research, as a result of this evolution of the performing arts. It is a form of theater that emerged in the brazilian context, snatching public attention in alternative spaces, theaters and, as it should be, also on the Internet, often confused with the Stand-up Comedy. It is necessary a research that delimitate and pursue to identify the essential characteristics of the brazilian One- Man Show, not only by the absence of theoretical references concerning this, but also to understand some aspects of the brazilian scene and the situation of laughter and comedy in it. In the first chapter, a discussion about comedy and laughter in classical antiquity is presented, using the writings of Plato and Aristotle as a starting point; in the second, some of the main classical theories of laughter are reviewed, attempting to identify the general characteristics that enable to understand the construction of the comedy; the third chapter generally dicusses about the moment of the brazilian theatrical scene in which emerges the One-man Show; and in the fourth chapter, there is an explanation about this phenomenon and a description of the practical exercise titled Experimento One-person Show: Damas