The fluorescence detector of the Pierre Auger Observatory

The Pierre Auger Observatory is a hybrid detector for ultra-high energy cosmic rays. It combines a surface array to measure secondary particles at ground level together with a fluorescence detector to measure the development of air showers in the atmosphere above the array. The fluorescence detector comprises 24 large telescopes specialized for measuring the nitrogen fluorescence caused by charged particles of cosmic ray air showers. In this paper we describe the components of the fluorescence detector including its optical system, the design of the camera, the electronics, and the systems for relative and absolute calibration. We also discuss the operation and the monitoring of the detector. Finally, we evaluate the detector performance and precision of shower reconstructions. (C) 2010 Elsevier B.V All rights reserved.

A study of the effect of molecular and aerosol conditions in the atmosphere on air fluorescence measurements at the Pierre Auger Observatory

The air fluorescence detector of the Pierre Auger Observatory is designed to perforin calorimetric measurements of extensive air showers created by Cosmic rays of above 10(18) eV. To correct these measurements for the effects introduced by atmospheric fluctuations, the Observatory contains a group Of monitoring instruments to record atmospheric conditions across the detector site, ail area exceeding 3000 km(2). The atmospheric data are used extensively in the reconstruction of air showers, and are particularly important for the correct determination of shower energies and the depths of shower maxima. This paper contains a summary of the molecular and aerosol conditions measured at the Pierre Auger Observatory since the start of regular operations in 2004, and includes a discussion of the impact of these measurements oil air shower reconstructions. Between 10(18) and 10(20) eV, the systematic Uncertainties due to all atmospheric effects increase from 4% to 8% in measurements of shower energy, and 4 g cm(-2) to 8 g cm(-2) in measurements of the shower maximum. (C) 2010 Elsevier B.V. All rights reserved.

O paradigma orgânico e seus reflexos no indivíduo, na sociedade, no estado e nas organizações

o comportamento do homem está influenciado por vários fatores, dentre eles as necessidades básicas, a razão, o coração e a consciência. Para modificar o comportamento do homem com vistas a um comportamento mais cooperativo, faz-se necessário agir sobre algum desses fatores. Do ponto de vista ético o fator que deve ser trabalhado é a consciência, que permitiria o surgimento da estrutura organizacional orgânica. A estrutura orgânica permitiria às organizações, ao Estado e à sociedade, ter um relacionamento mais adequado com uma realidade social, universal e cósmica que se revela harmônica em seus princípios. A estrutura orgânica organizacional parte das propriedades da metáfora orgânica, presente em qualquer sistema orgânico (biológico, atômico e cósmico), e surge a partir dos seguintes pressupostos: a realidade pode ser representada como uma estrutura em rede orgânica, e o comportamento das pessoas vem determinado pelo nível de consciência. A estrutura orgânica possui os princípios de Autopoiesis e do Holograma, e tem uma série de propriedades aplicáveis em nível organizacional, tais como adaptação, evolução, flexibilidade e homeostase. A sociedade orgânica viria modelada pelos princípios e propriedades da estrutura orgânica, que induziriam o surgimento de comportamentos cooperativos e solidários dentro das instituições sociais, sobretudo aqueles relacionados com a organização do trabalho e a organização da economia. Adicionalmente, o paradigma orgânico conduziria ao estabelecimento das comunidades orgânicas. O Estado orgânico surgiria como decorrência de uma situação em que, o paradigma burocrático revelando-se inadequado para seu funcionamento, permitiria sua organização sob o paradigma orgânico. A substituição do paradigma organizacional burocrático-mecanicista vigente pelo paradigma orgânico, ocorreria de acordo com uma das seguintes alternativas: a) um processo intencional de mudanças minimalistas intercalado com ações radicais pontuais; ou b) uma situação de crise, em decorrência do impedimento do fluxo de mudanças naturais não implementadas. Propõe-se, assim, o paradigma orgânico como ponto de partida indispensável a mudanças conducentes ao bem estar individual e coletivo.

A relação homem-mundo em René Descartes e no Zen-Budismo

Este trabalho procura justapor duas visões do homem no mundo, a cartesiana e a zen-budista, ressaltando o aspecto fragmentador da primeira e o aspecto integrador da segunda. O objetivo básico é contribuir para maior articulação e integração do homem contemporâneo através de três movimentos. Primeiro, através da critica à concepçao racionalista, mecânica, prepotente e antinatural, fundada na lógica dual e antitética do paradigma da ciência e do pensamento ocidental em boa parte construido por René Descartes; Segundo, através da divulgação e da exposição enfática, em nosso meio acadêmico ocidental, da metafisica e da mística budistas, especialmente em sua versão Zen, que compreende o mundo em permanente transformação e construção como um todo articulado ao equilibrio universal, no qual as palavras, os conhecimentos e a percepção são meros signos passageiros que escondem a realidade cósmica. O movimento final pretende negar uma visão maniqueísta da realidade onde a oposição não é vista como a liquidação de um dos termos pelo outro, mas como a busca de uma nova síntese: a gestação, enfim, de um novo referencial do mundo - e aqui apenas se levanta a questão - a ser construído, quem sabe, a partir da integração dos paradigmas caracterizados hoje como ocidental e oriental.

Ampliação de movimentos na dança circular com pessoas com deficiência visual

This paper aims at studying how circular dance can afford to sight-disabled peoples movement and how they can learn to cope with the deep movement of relation, consciousness, appropriation and communion with the world. Inside circular dance, a cosmic metaphor, is inscribed the movement of the world, which tells and changes amorously the human history. In the works of Paulo Freire and Maurice Merleau-Ponty one can find the necessary support to discuss, as long as possible, movement and existence. Research-action is used as a methodological approach whose empirical center is placed on the Institute of Education and Rehabilitation of Blind, in Natal, which shelters eight sightdisabled adults. The research s data reveal that the practice of circular dance concurs to enlarge the movement of the research s subjects, to develop a more accurate perception of their selves and of their own capacities, as well as improve the relations Me/Others, Me/World, which require a context of differences. The study has revealed that the practice of dance develops a better perception of the limits and surpasses as a human condition and, in consequence, the discovery of one s own body and the other s body as a resource of lessons and representations of the self and of the world. It lets out the development of a new way of thinking and coping with discrimination surrounding the disabled persons. In movement, in circular dance, the barrier between sight disablement and vision loses force.

ESR dating of pleistocene mammal teeth and its implications for the biostratigraphy and geological evolution of the coastal plain, Rio Grande do Sul, southern Brazil

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Acelaração do universo e criação gravitacional de matéria escura fria: novos modelos e testes observacionais

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

Criação da matéria em cosmologias com velocidade da luz variável e eletrônico não-linear

In this work we obtain the cosmological solutions and investigate the thermodynamics of matter creation in two diferent contexts. In the first we propose a cosmological model with a time varying speed of light c. We consider two diferent time dependence of c for a at Friedmann-Robertson- Walker (FRW) universe. We write the energy conservation law arising from Einstein equations and study how particles are created as c decreases with cosmic epoch. The variation of c is coupled to a cosmological Λ term and both singular and non-singular solutions are possible. We calculate the "adiabatic" particle creation rate and the total number of particles as a function of time and find the constrains imposed by the second law of thermodynamics upon the models. In the second scenario, we study the nonlinearity of the electrodynamics as a source of matter creation in the cosmological models with at FRW geometry. We write the energy conservation law arising from Einstein field equations with cosmological term Λ, solve the field equations and study how particles are created as the magnetic field B changes with cosmic epoch. We obtain solutions for the adiabatic particle creation rate, the total number of particles and the scale factor as a function of time in three cases: Λ = 0, Λ = constant and Λ α H2 (cosmological term proportional to the Hubble parameter). In all cases, the second law of thermodynamics demands that the universe is not contracting (H ≥ 0). The first two solutions are non-singular and exhibit in ationary periods. The third case studied allows an always in ationary universe for a suficiently large cosmological term

Setor escuro do universo: uma análise termodinâmica

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 μ and a varying EoS parameter of the type ω(a) = ω0 + 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 μ 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 ω(a). In particular, we find that a phantom-like behavior ω(a) < −1 is allowed only when the chemical potential is a negative quantity (μ < 0). Thermodynamically speaking, a complete treatment has been proposed, when we address the interaction between matter and energy dark

Efeitos não-gaussianos em astrofísica e cosmologia

The recent astronomical observations indicate that the universe has null spatial curvature, is accelerating and its matter-energy content is composed by circa 30% of matter (baryons + dark matter) and 70% of dark energy, a relativistic component with negative pressure. However, in order to built more realistic models it is necessary to consider the evolution of small density perturbations for explaining the richness of observed structures in the scale of galaxies and clusters of galaxies. The structure formation process was pioneering described by Press and Schechter (PS) in 1974, by means of the galaxy cluster mass function. The PS formalism establishes a Gaussian distribution for the primordial density perturbation field. Besides a serious normalization problem, such an approach does not explain the recent cluster X-ray data, and it is also in disagreement with the most up-to-date computational simulations. In this thesis, we discuss several applications of the nonextensive q-statistics (non-Gaussian), proposed in 1988 by C. Tsallis, with special emphasis in the cosmological process of the large structure formation. Initially, we investigate the statistics of the primordial fluctuation field of the density contrast, since the most recent data from the Wilkinson Microwave Anisotropy Probe (WMAP) indicates a deviation from gaussianity. We assume that such deviations may be described by the nonextensive statistics, because it reduces to the Gaussian distribution in the limit of the free parameter q = 1, thereby allowing a direct comparison with the standard theory. We study its application for a galaxy cluster catalog based on the ROSAT All-Sky Survey (hereafter HIFLUGCS). We conclude that the standard Gaussian model applied to HIFLUGCS does not agree with the most recent data independently obtained by WMAP. Using the nonextensive statistics, we obtain values much more aligned with WMAP results. We also demonstrate that the Burr distribution corrects the normalization problem. The cluster mass function formalism was also investigated in the presence of the dark energy. In this case, constraints over several cosmic parameters was also obtained. The nonextensive statistics was implemented yet in 2 distinct problems: (i) the plasma probe and (ii) in the Bremsstrahlung radiation description (the primary radiation from X-ray clusters); a problem of considerable interest in astrophysics. In another line of development, by using supernova data and the gas mass fraction from galaxy clusters, we discuss a redshift variation of the equation of state parameter, by considering two distinct expansions. An interesting aspect of this work is that the results do not need a prior in the mass parameter, as usually occurs in analyzes involving only supernovae data.Finally, we obtain a new estimate of the Hubble parameter, through a joint analysis involving the Sunyaev-Zeldovich effect (SZE), the X-ray data from galaxy clusters and the baryon acoustic oscillations. We show that the degeneracy of the observational data with respect to the mass parameter is broken when the signature of the baryon acoustic oscillations as given by the Sloan Digital Sky Survey (SDSS) catalog is considered. Our analysis, based on the SZE/X-ray data for a sample of 25 galaxy clusters with triaxial morphology, yields a Hubble parameter in good agreement with the independent studies, provided by the Hubble Space Telescope project and the recent estimates of the WMAP

Anisotropias da radiação cósmica de fundo e vínculos em modelos com decaimento do vácuo

Many astronomical observations in the last few years are strongly suggesting that the current Universe is spatially flat and dominated by an exotic form of energy. This unknown energy density accelerates the universe expansion and corresponds to around 70% of its total density being usually called Dark Energy or Quintessence. One of the candidates to dark energy is the so-called cosmological constant (Λ) which is usually interpreted as the vacuum energy density. However, in order to remove the discrepancy between the expected and observed values for the vacuum energy density some current models assume that the vacuum energy is continuously decaying due to its possible coupling with the others matter fields existing in the Cosmos. In this dissertation, starting from concepts and basis of General Relativity Theory, we study the Cosmic Microwave Background Radiation with emphasis on the anisotropies or temperature fluctuations which are one of the oldest relic of the observed Universe. The anisotropies are deduced by integrating the Boltzmann equation in order to explain qualitatively the generation and c1assification of the fluctuations. In the following we construct explicitly the angular power spectrum of anisotropies for cosmologies with cosmological constant (ΛCDM) and a decaying vacuum energy density (Λ(t)CDM). Finally, with basis on the quadrupole moment measured by the WMAP experiment, we estimate the decaying rates of the vacuum energy density in matter and in radiation for a smoothly and non-smoothly decaying vacuum

Teorias f(R) de gravidade na formulação de Palatini

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

Measuring the spectra of high energy neutrinos with a kilometer-scale neutrino telescope

We investigate the potential of a future kilometer-scale neutrino telescope, such as the proposed IceCube detector in the South Pole, to measure and disentangle the yet unknown components of the cosmic neutrino flux, the prompt atmospheric neutrinos coming from the decay of charmed particles and the extra-galactic neutrinos in the 10 TeV to 1 EeV energy range. Assuming a power law type spectra, dphi(nu)/dE(nu)similar toalphaE(nu)(beta), we quantify the discriminating power of the IceCube detector and discuss how well we can determine magnitude (alpha) as well as slope (beta) of these two components of the high energy neutrino spectrum, taking into account the background coming from the conventional atmospheric neutrinos.

Age constraints and fine tuning in variable-mass particle models

VAMP (variable-mass particle) scenarios, in which the mass of the cold dark matter particles is a function of the scalar field responsible for the present acceleration of the Universe, have been proposed as a solution to the cosmic coincidence problem, since in the attractor regime both dark energy and dark matter scale in the same way. We find that only a narrow region in parameter space leads to models with viable values for the Hubble constant and dark energy density today. In the allowed region, the dark energy density starts to dominate around the present epoch and consequently such models cannot solve the coincidence problem. We show that the age of the Universe in this scenario is considerably higher than the age for noncoupled dark energy models, and conclude that more precise independent measurements of the age of the Universe would be useful in distinguishing between coupled and noncoupled dark energy models.

Godel type solution in teleparallel gravity

The stationary cosmological model without closed timelike curves of Godel type is obtained for the ideal dust matter source within the framework of the teleparallel gravity. For a specific choice of the teleparallel gravity parameters, this solution reproduces the causality violating stationary Godel solution in general relativity, in accordance with the teleparallel equivalent of general relativity. The relation between the axial-vector torsion and the cosmic vorticity is clarified. (C) 2004 Elsevier B.V. All rights reserved.