13 resultados para COSMOLOGY

em Universidade Federal do Rio Grande do Norte(UFRN)


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This participative research interested in the social praxis attempts to understand the moral principles that set the magic rituals and the places of worship of three jurema centers of the potiguar region of Canguaretama. Among other inner particularly aspects of each focused catimbó-jurema center, it is being discussed the collective standards involved in the reliance and fellowship values assumed in the private magical gatherings by the juremeiras leaders and their partners, in contrast to the prestige seeking and the individualism that influence both the symbolic competitions and the witchcraft works that link these agents to the broader catimbozeiro universe of this region. Finally, the moral practices which make part of the juremeiro left-right dualism are investigated based on the understanding that the referred native pantheonic-ritual dichotomy does not necessarily express two moralities substantially adversed in terms of benefits or harms, but a series of moral actions subject to the specular logic of the tit-for tat. Thus, this research seeks to prove that this moral structure of symbolic reciprocity, as well as the witchcraft centrality in the catimbozeiro world, finds a certain causal link in a world view which guiding principle is the ontological evil of the catholic cosmology

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This thesis aims at producing knowledge by putting together various theories and empirical analyses. In other words, from an interdisciplinary approach within the Social Sciences and having as background Communication and the City, this work presents, in each chapter, a disciplinary field Literature, Architecture, History and Geography , with which they relate, exhibits its theoretical pillars and performs a case study as a factual and critical contribution, considering the urban spaces of Rio de Janeiro, Brasília, São Paulo and Natal. By so doing, the thesis covers the period from the end of the XIX to the beginning of the XXI Century. Overall, the thesis is an interconnected and dialogic set that points to a cosmology of plural knowledge

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Recent astronomical observations (involving supernovae type Ia, cosmic background radiation anisotropy and galaxy clusters probes) have provided strong evidence that the observed universe is described by an accelerating, flat model whose space-time properties can be represented by the FriedmannRobertsonWalker (FRW) metric. However, the nature of the substance or mechanism behind the current cosmic acceleration remains unknown and its determination constitutes a challenging problem for modern cosmology. In the general relativistic description, an accelerat ing regime is usually obtained by assuming the existence of an exotic energy component endowed with negative pressure, called dark energy, which is usually represented by a cosmological constant ¤ associated to the vacuum energy density. All observational data available so far are in good agreement with the concordance cosmic ¤CDM model. Nevertheless, such models are plagued with several problems thereby inspiring many authors to propose alternative candidates in the relativistic context. In this thesis, a new kind of accelerating flat model with no dark energy and fully dominated by cold dark matter (CDM) is proposed. The number of CDM particles is not conserved and the present accelerating stage is a consequence of the negative pressure describing the irreversible process of gravitational particle creation. In order to have a transition from a decelerating to an accelerating regime at low redshifts, the matter creation rate proposed here depends on 2 parameters (y and ߯): the first one identifies a constant term of the order of H0 and the second one describes a time variation proportional to he Hubble parameter H(t). In this scenario, H0 does not need to be small in order to solve the age problem and the transition happens even if there is no matter creation during the radiation and part of the matter dominated phase (when the ß term is negligible). Like in flat ACDM scenarios, the dimming of distant type Ia supernovae can be fitted with just one free parameter, and the coincidence problem plaguing the models driven by the cosmological constant. ACDM is absent. The limits endowed with with the existence of the quasar APM 08279+5255, located at z = 3:91 and with an estimated ages between 2 and 3 Gyr are also investigated. In the simplest case (ß = 0), the model is compatible with the existence of the quasar for y > 0:56 whether the age of the quasar is 2.0 Gyr. For 3 Gyr the limit derived is y > 0:72. New limits for the formation redshift of the quasar are also established

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In the Einstein s theory of General Relativity the field equations relate the geometry of space-time with the content of matter and energy, sources of the gravitational field. This content is described by a second order tensor, known as energy-momentum tensor. On the other hand, the energy-momentum tensors that have physical meaning are not specified by this theory. In the 700s, Hawking and Ellis set a couple of conditions, considered feasible from a physical point of view, in order to limit the arbitrariness of these tensors. These conditions, which became known as Hawking-Ellis energy conditions, play important roles in the gravitation scenario. They are widely used as powerful tools for analysis; from the demonstration of important theorems concerning to the behavior of gravitational fields and geometries associated, the gravity quantum behavior, to the analysis of cosmological models. In this dissertation we present a rigorous deduction of the several energy conditions currently in vogue in the scientific literature, such as: the Null Energy Condition (NEC), Weak Energy Condition (WEC), the Strong Energy Condition (SEC), the Dominant Energy Condition (DEC) and Null Dominant Energy Condition (NDEC). Bearing in mind the most trivial applications in Cosmology and Gravitation, the deductions were initially made for an energy-momentum tensor of a generalized perfect fluid and then extended to scalar fields with minimal and non-minimal coupling to the gravitational field. We also present a study about the possible violations of some of these energy conditions. Aiming the study of the single nature of some exact solutions of Einstein s General Relativity, in 1955 the Indian physicist Raychaudhuri derived an equation that is today considered fundamental to the study of the gravitational attraction of matter, which became known as the Raychaudhuri equation. This famous equation is fundamental for to understanding of gravitational attraction in Astrophysics and Cosmology and for the comprehension of the singularity theorems, such as, the Hawking and Penrose theorem about the singularity of the gravitational collapse. In this dissertation we derive the Raychaudhuri equation, the Frobenius theorem and the Focusing theorem for congruences time-like and null congruences of a pseudo-riemannian manifold. We discuss the geometric and physical meaning of this equation, its connections with the energy conditions, and some of its several aplications.

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We investigate the cosmology of the vacuum energy decaying into cold dark matter according to thermodynamics description of Alcaniz & Lima. We apply this model to analyze the evolution of primordial density perturbations in the matter that gave rise to the first generation of structures bounded by gravity in the Universe, called Population III Objects. The analysis of the dynamics of those systems will involve the calculation of a differential equation system governing the evolution of perturbations to the case of two coupled fluids (dark matter and baryonic matter), modeled with a Top-Hat profile based in the perturbation of the hydrodynamics equations, an efficient analytical tool to study the properties of dark energy models such as the behavior of the linear growth factor and the linear growth index, physical quantities closely related to the fields of peculiar velocities at any time, for different models of dark energy. The properties and the dynamics of current Universe are analyzed through the exact analytical form of the linear growth factor of density fluctuations, taking into account the influence of several physical cooling mechanisms acting on the density fluctuations of the baryonic component of matter during the evolution of the clouds of matter, studied from the primordial hydrogen recombination. This study is naturally extended to more general models of dark energy with constant equation of state parameter in a flat Universe

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We address the generalization of thermodynamic quantity q-deformed by q-algebra that describes a general algebra for bosons and fermions . The motivation for our study stems from an interest to strengthen our initial ideas, and a possible experimental application. On our journey, we met a generalization of the recently proposed formalism of the q-calculus, which is the application of a generalized sequence described by two parameters deformation positive real independent and q1 and q2, known for Fibonacci oscillators . We apply the wellknown problem of Landau diamagnetism immersed in a space D-dimensional, which still generates good discussions by its nature, and dependence with the number of dimensions D, enables us future extend its application to systems extra-dimensional, such as Modern Cosmology, Particle Physics and String Theory. We compare our results with some experimentally obtained performing major equity. We also use the formalism of the oscillators to Einstein and Debye solid, strengthening the interpretation of the q-deformation acting as a factor of disturbance or impurity in a given system, modifying the properties of the same. Our results show that the insertion of two parameters of disorder, allowed a wider range of adjustment , i.e., enabling change only the desired property, e.g., the thermal conductivity of a same element without the waste essence

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The recent observational advances of Astronomy and a more consistent theoretical framework turned Cosmology in one of the most exciting frontiers of contemporary science. In this thesis, homogeneous and inhomogeneous Universe models containing dark matter and different kinds of dark energy are confronted with recent observational data. Initially, we analyze constraints from the existence of old high redshift objects, Supernovas type Ia and the gas mass fraction of galaxy clusters for 2 distinct classes of homogeneous and isotropic models: decaying vacuum and X(z)CDM cosmologies. By considering the quasar APM 08279+5255 at z = 3.91 with age between 2-3 Gyr, we obtain 0,2 < OM < 0,4 while for the j3 parameter which quantifies the contribution of A( t) is restricted to the intervalO, 07 < j3 < 0,32 thereby implying that the minimal age of the Universe amounts to 13.4 Gyr. A lower limit to the quasar formation redshift (zJ > 5,11) was also obtained. Our analyzes including flat, closed and hyperbolic models show that there is no an age crisis for this kind of decaying A( t) scenario. Tests from SN e Ia and gas mass fraction data were realized for flat X(z)CDM models. For an equation of state, úJ(z) = úJo + úJIZ, the best fit is úJo = -1,25, úJl = 1,3 and OM = 0,26, whereas for models with úJ(z) = úJo+úJlz/(l+z), we obtainúJo = -1,4, úJl = 2,57 and OM = 0,26. In another line of development, we have discussed the influence of the observed inhomogeneities by considering the Zeldovich-Kantowski-DyerRoeder (ZKDR) angular diameter distance. By applying the statistical X2 method to a sample of angular diameter for compact radio sources, the best fit to the cosmological parameters for XCDM models are OM = O, 26,úJ = -1,03 and a = 0,9, where úJ and a are the equation of state and the smoothness parameters, respectively. Such results are compatible with a phantom energy component (úJ < -1). The possible bidimensional spaces associated to the plane (a , OM) were restricted by using data from SNe Ia and gas mass fraction of galaxy clusters. For Supernovas the parameters are restricted to the interval 0,32 < OM < 0,5(20") and 0,32 < a < 1,0(20"), while to the gas mass fraction we find 0,18 < OM < 0,32(20") with alI alIowed values of a. For a joint analysis involving Supernovas and gas mass fraction data we obtained 0,18 < OM < 0,38(20"). In general grounds, the present study suggests that the influence of the cosmological inhomogeneities in the matter distribution need to be considered with more detail in the analyses of the observational tests. Further, the analytical treatment based on the ZKDR distance may give non-negligible corrections to the so-calIed background tests of FRW type cosmologies

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Understanding the way in which large-scale structures, like galaxies, form remains one of the most challenging problems in cosmology today. The standard theory for the origin of these structures is that they grew by gravitational instability from small, perhaps quantum generated, °uctuations in the density of dark matter, baryons and photons over an uniform primordial Universe. After the recombination, the baryons began to fall into the pre-existing gravitational potential wells of the dark matter. In this dissertation a study is initially made of the primordial recombination era, the epoch of the formation of the neutral hydrogen atoms. Besides, we analyzed the evolution of the density contrast (of baryonic and dark matter), in clouds of dark matter with masses among 104M¯ ¡ 1010M¯. In particular, we take into account the several physical mechanisms that act in the baryonic component, during and after the recombination era. The analysis of the formation of these primordial objects was made in the context of three models of dark energy as background: Quintessence, ¤CDM(Cosmological Constant plus Cold Dark Matter) and Phantom. We show that the dark matter is the fundamental agent for the formation of the structures observed today. The dark energy has great importance at that epoch of its formation

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Dark matter is a fundamental ingredient of the modern Cosmology. It is necessary in order to explain the process of structures formation in the Universe, rotation curves of galaxies and the mass discrepancy in clusters of galaxies. However, although many efforts, in both aspects, theoretical and experimental, have been made, the nature of dark matter is still unknown and the only convincing evidence for its existence is gravitational. This rises doubts about its existence and, in turn, opens the possibility that the Einstein’s gravity needs to be modified at some scale. We study, in this work, the possibility that the Eddington-Born-Infeld (EBI) modified gravity provides en alternative explanation for the mass discrepancy in clusters of galaxies. For this purpose we derive the modified Einstein field equations and find their solutions to a spherical system of identical and collisionless point particles. Then, we took into account the collisionless relativistic Boltzmann equation and using some approximations and assumptions for weak gravitational field, we derived the generalized virial theorem in the framework of EBI gravity. In order to compare the predictions of EBI gravity with astrophysical observations we estimated the order of magnitude of the geometric mass, showing that it is compatible with present observations. Finally, considering a power law for the density of galaxies in the cluster, we derived expressions for the radial velocity dispersion of the galaxies, which can be used for testing some features of the EBI gravity.

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Dark matter is a fundamental ingredient of the modern Cosmology. It is necessary in order to explain the process of structures formation in the Universe, rotation curves of galaxies and the mass discrepancy in clusters of galaxies. However, although many efforts, in both aspects, theoretical and experimental, have been made, the nature of dark matter is still unknown and the only convincing evidence for its existence is gravitational. This rises doubts about its existence and, in turn, opens the possibility that the Einstein’s gravity needs to be modified at some scale. We study, in this work, the possibility that the Eddington-Born-Infeld (EBI) modified gravity provides en alternative explanation for the mass discrepancy in clusters of galaxies. For this purpose we derive the modified Einstein field equations and find their solutions to a spherical system of identical and collisionless point particles. Then, we took into account the collisionless relativistic Boltzmann equation and using some approximations and assumptions for weak gravitational field, we derived the generalized virial theorem in the framework of EBI gravity. In order to compare the predictions of EBI gravity with astrophysical observations we estimated the order of magnitude of the geometric mass, showing that it is compatible with present observations. Finally, considering a power law for the density of galaxies in the cluster, we derived expressions for the radial velocity dispersion of the galaxies, which can be used for testing some features of the EBI gravity.

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Since long ago that the religious manifestations are considered important items in various social media. In this sense, we are interested in understanding the strong denominational plurality, and the emergence of new movements / events and forms of Christianity in Brazil, which therefore is a reflection of what happens in the rest of the globalized world. Such interest is covered by the assumption that religiosity and social media are built on mutual and interconnected way, which allows us to understand that social cosmology presents itself as a fertile space privileged and to verify the interactions pertaining to the binomial: religion and society. The Protestantism is divided into three main streams: Historical, Pentecostal and Neo-Pentecostal. Each current of Protestantism emerged to adapt to social cosmology of historical ages, from the Reformation to the present day, forming institutions with certain ethical and moral stances. In this sense, it is necessary to research and understand how the historical Protestant, Pentecostal and neo-Pentecostal were implanted in Brazil. From this we believe to be interesting problematize accurately the following: How have the processes of formation of strands / evangelical movements in Brazil? These movements are still holding their "classic robes" or hybreeding their borders? What are the modulations in the religious transit demonstrate that this probable hybridization? If there is, indeed, a hybridization between the Evangelical means, we can put it is provoked only by a logic of "market of symbolic goods of religion" in the world today? Nowadays, we are experiencing a period of change cosmological, from Modern to Postmodern (caosmológic). This last is therefore characterized by secularization, the fracture, the mutilation, the diversity of subjectivities. And thinking about is this "spirit of the times" we take as the main its theoretical references of this study, the Italian philosopher and thinker of postmodernity Gianni Vattimo featuring postmodernity with the cosmology of fragile / pensiero debole Thought and post-metaphysical, that is which enhances the appearance of more plural institutions and non-absolute. To do so, he makes use of the philosophies of German, Nietzsche and Heidegger. Finally, it must be said that this grounded theoretical framework, raise the hypothesis that the Protestantism tends to "injure anymore" by the influence of postmodern social episteme, providing thereby the emergence of a new hybrid framework has not yet nominated and can move between the three major currents of world Protestantism, with features in converged aspects of the same.

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Since long ago that the religious manifestations are considered important items in various social media. In this sense, we are interested in understanding the strong denominational plurality, and the emergence of new movements / events and forms of Christianity in Brazil, which therefore is a reflection of what happens in the rest of the globalized world. Such interest is covered by the assumption that religiosity and social media are built on mutual and interconnected way, which allows us to understand that social cosmology presents itself as a fertile space privileged and to verify the interactions pertaining to the binomial: religion and society. The Protestantism is divided into three main streams: Historical, Pentecostal and Neo-Pentecostal. Each current of Protestantism emerged to adapt to social cosmology of historical ages, from the Reformation to the present day, forming institutions with certain ethical and moral stances. In this sense, it is necessary to research and understand how the historical Protestant, Pentecostal and neo-Pentecostal were implanted in Brazil. From this we believe to be interesting problematize accurately the following: How have the processes of formation of strands / evangelical movements in Brazil? These movements are still holding their "classic robes" or hybreeding their borders? What are the modulations in the religious transit demonstrate that this probable hybridization? If there is, indeed, a hybridization between the Evangelical means, we can put it is provoked only by a logic of "market of symbolic goods of religion" in the world today? Nowadays, we are experiencing a period of change cosmological, from Modern to Postmodern (caosmológic). This last is therefore characterized by secularization, the fracture, the mutilation, the diversity of subjectivities. And thinking about is this "spirit of the times" we take as the main its theoretical references of this study, the Italian philosopher and thinker of postmodernity Gianni Vattimo featuring postmodernity with the cosmology of fragile / pensiero debole Thought and post-metaphysical, that is which enhances the appearance of more plural institutions and non-absolute. To do so, he makes use of the philosophies of German, Nietzsche and Heidegger. Finally, it must be said that this grounded theoretical framework, raise the hypothesis that the Protestantism tends to "injure anymore" by the influence of postmodern social episteme, providing thereby the emergence of a new hybrid framework has not yet nominated and can move between the three major currents of world Protestantism, with features in converged aspects of the same.

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This participative research interested in the social praxis attempts to understand the moral principles that set the magic rituals and the places of worship of three jurema centers of the potiguar region of Canguaretama. Among other inner particularly aspects of each focused catimbó-jurema center, it is being discussed the collective standards involved in the reliance and fellowship values assumed in the private magical gatherings by the juremeiras leaders and their partners, in contrast to the prestige seeking and the individualism that influence both the symbolic competitions and the witchcraft works that link these agents to the broader catimbozeiro universe of this region. Finally, the moral practices which make part of the juremeiro left-right dualism are investigated based on the understanding that the referred native pantheonic-ritual dichotomy does not necessarily express two moralities substantially adversed in terms of benefits or harms, but a series of moral actions subject to the specular logic of the tit-for tat. Thus, this research seeks to prove that this moral structure of symbolic reciprocity, as well as the witchcraft centrality in the catimbozeiro world, finds a certain causal link in a world view which guiding principle is the ontological evil of the catholic cosmology