Orientador: Alberto Vazquez Saa / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Fisica Gleb Wataghin / Made available in DSpace on 2018-08-13T05:40:24Z (GMT). No. of bitstreams: 1 Froes_AndreLuisDelvas_M.pdf: 1355314 bytes, checksum: edf9f0fa41f3a8e6e519f2b958be6603 (MD5) Previous issue date: 2009 / Resumo: O foco do presente trabalho é a realização de períodos inflacionários baseados em campos vetoriais. Os conhecimentos necessários para atingir esse objetivo foram introduzidos de maneira sistemática, na ordem em que o autor julgou mais lógica. No primeiro capítulo são descritos numerosos detalhes acerca de nosso Universo e da capacidade atual de observá-lo. No segundo, apresenta-se o modelo cosmológico padrão. São também apresentados os alguns dos principais resultados da Relatividade Geral, a partir dos quais constroem-se os fundamentos teóricos da Cosmologia. No terceiro capítulo a teoria in acionária é estudada, e são comentados seus resultados mais importantes e modelos mais conhecidos, baseados em campos escalares. No quarto capítulo inicia-se o estudo de períodos in acionários utilizando campos vetoriais. Esse assunto despertou a atenção e gerou diversas publicações ao longo do ano de 2008. Por fim, são apresentadas as impressões do autor e as perspectivas futuras da área são delineadas. / Abstract: The main point of the present work is the realisation of in ationary periods based on vector fields. The knowledge needed to achieve this objective were introduced in a systematic manner, in the order that the author found more logical. In the first chapter numerous details about our universe and the present capacity to observe it were described. In the second, the standard model of cosmology is presented. Some of the most important results of General Relativity and observational cosmology are also presented, and on these grounds the theoretical fundaments of Cosmology are estabilished. In the third chapter in ationary cosmology is studied, and its most important results and some well known models based on scalar fields are presented. In the fourth chapter begins the study of in ationary periods that uses vector fields. This subject attracted attention and generated many papers in the year of 2008. At last, the author¿s impressions and future perspectives in the subject are presented. / Mestrado / Cosmologia / Mestre em Física

Galaxy redshift surveys are powerful probes of cosmology. Yet, in order to fully exploit the information contained in galaxy surveys, we need to improve upon our understanding of the structure formation in the Universe. Galaxies are formed/observed at late times when the density field is no longer linear so that understanding non-linearities is essential. In this thesis, we show that, at high redshifts, we can accurately model the galaxy power spectrum in redshift space by using the standard cosmological perturbation theory. Going beyond the power spectrum, we can use the three-point function, or the bispectrum, to gain important information on the early universe as well as on the galaxy formation via measurements of primordial non-Gaussianity and galaxy bias. We show that the galaxy bispectrum is more sensitive to primordial non-Gaussianities than previously recognized, making high-redshift galaxy surveys a particularly potent probe of the physics of inflation. Weak lensing offers yet another way of probing cosmology. By cross correlating the angular position of galaxies with the shear measurement from galaxy lensing or CMB lensing, we also show that one can obtain the information on cosmological distance scale, the galaxy bias, and the primordial non Gaussianity from weak lensing method. / text

Thesis (Ph.D.)--University of Delaware, 2007. / Principal faculty advisor: Qaisar Shafi, Dept. of Physics & Astronomy. Includes bibliographical references.

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Inflationary predictions for the power spectrum of the curvature perturbation have been verified to an excellent degree, leaving many models compatible with observations. In this thesis we studied third-order correlations, that might allow one to further distinguish between inflationary models. From all the possible extensions of the standard inflationary model, we chose to study two-field models with canonical kinetic terms and flat field space. The new feature is the presence of the so-called isocurvature perturbation. Its interplay with the adiabatic perturbation outside the horizon gives birth to non-linearities characteristic of multiple-field models. In this context, we established the second-order gauge-invariant form of the adiabatic and isocurvature perturbation and found the third-order action that describes their interactions. Furthermore, we built on and elaborated the long-wavelength formalism in order to acquire an expression for the parameter of non-Gaussianity fNL as a function of the potential of the fields. We next used this formula to study analytically, within the slow-roll hypothesis, general classes of potentials and verified our results numerically for the exact theory. From this study, we deduced general conclusions about the properties of fNL, its magnitude depending on the characteristics of the field trajectory and the isocurvature component, as well as its dependence on the magnitude and relative size of the three momenta of which the three-point correlator is a function.

Thesis (Ph. D.)--University of Texas at Austin, 2006. / Vita. Includes bibliographical references.

京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第22245号 / 理博第4559号 / 新制||理||1655(附属図書館) / 京都大学大学院理学研究科物理学・宇宙物理学専攻 / (主査)教授 田中 貴浩, 教授 川合 光, 教授 向山 信治 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DFAM

京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第20656号 / 理博第4321号 / 新制||理||1621(附属図書館) / 京都大学大学院理学研究科物理学・宇宙物理学専攻 / (主査)教授 佐々木 節, 教授 田中 貴浩, 教授 川合 光 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DFAM

Hybrid models of inflation are particularly interesting and well motivated, since easily embedded in various high energy frameworks like supersymmetry/supergravity, Grand Unified Theories or extra-dimensional theories. If the original hybrid model is often considered as disfavored, because it generically predicts a blue spectrum of scalar perturbations, realistic hybrid models can be in agreement with CMB observations. The dynamics of hybrid models is usually approximated by the evolution of a scalar field slowly rolling along a nearly flat valley. Inflation ends with a waterfall phase, due to a tachyonic instability. This final phase is usually assumed to be nearly instantaneous. <p> <p>In this thesis, we go beyond these approximations and analyze the exact 2-field non-linear dynamics of hybrid models. Several non trivial effects are put in evidence: 1) the possible violation of the slow-roll conditions along the valley induce the non existence of inflation at small field values. Provided super-planckian fields, the scalar spectrum of the original model is red, in agreement with CMB observations, independently of the position of the critical instability point. 2) Contrary to what was thought, the initial field values leading to inflation are not fine-tuned along the valley but also occupy a considerable part of the field space exterior to it. They form a complex connected structure with fractal boundaries that is the basin of attraction of the valley. Using bayesian methods, their distribution in the whole parameter space, including initial velocities, is studied. Natural bounds on the potential parameters are derived. 3) For the original model, after the field evolution along the valley, inflation continues for more than 60 e-folds along the waterfall trajectories in some part of the parameter space. Observable predictions are modified, and the scalar power spectrum of adiabatic perturbations is generically red, possibly in agreement with CMB observations. Moreover, topological defects are conveniently stretched outside the observable Universe. 4) The analysis of the initial conditions is extended to the case of a closed Universe, in which the initial singularity is replaced by a classical bounce. Contrary to some other scenarios, due to the attractor nature of the valley, the field values in the contracting phase do not need to be extremely fine-tuned to generate a bounce followed by a phase of hybrid inflation. <p> <p>In the third part of the thesis, we study how the present CMB constraints on the cosmological parameters could be ameliorated with the observation of the 21cm cosmic background from the dark ages and the reionization, by the future generation of giant radio-telescope. Assuming ideal foreground removals, forecasts on the cosmological parameters are determined for a characteristic Fast Fourier Transform Telescope experiment, by using both Fisher matrix and MCMC methods. / Doctorat en Sciences / info:eu-repo/semantics/nonPublished