Ce travail est concentré sur l'étude de la cosmologie primordiale et en particulier sur l'étude de l'inflation. Après une introduction sur la théorie standard du Big Bang, nous discutons de la physique du CMB et nous expliquons comment ses observations peuvent être utilisées pour définir des contraintes sur les modèles cosmologiques. Nous introduisons l'inflation et nous expliquons sa réalisation la plus simple. Nous présentons les observables et les contraintes expérimentales qui peuvent être utilisées pour mettre des contraintes sur les modèles d'inflation. La possibilité d'observer des ondes gravitationnelles primordiales (GW) produites au cours de l'inflation est examinée. Nous présentons les raisons pour définir une classification des modèles d'inflation et pour introduire le formalisme de la fonction 13 pour décrire l'inflation. En particulier nous expliquons pourquoi, dans ce cadre, nous pouvons naturellement définir un ensemble de classes d'universalité pour les modèles d'inflation. Les motivations théoriques pour soutenir la formulation de l'inflation en termes de ce formalisme sont présentées. Certains modèles généralisés d'inflation sont introduits et l'extension du formalisme de la fonction (3-formalisme à ces modèles est discutée. Enfin, nous nous concentrons sur l'étude des modèles où l’inflation (qui es assumé être pseudo-scalaire) est couplé non-minimalement à des champs de jauge abéliens qui peuvent être présents lors de l'inflation. L'analyse du problème est effectuée en utilisant une caractérisation de modèles d'inflation sur la base de leur comportement asymptotique. Un large éventail d'aspects théoriques et des conséquences d'observation est discuté. / This work is focused on the study of early time cosmology and in particular on the study of inflation. After an introduction on the standard Big Bang theory, we discuss the physics of CMB and we explain how its observations can be used to set constraints on cosmological models. We introduce inflation and we carry out its simplest realization by presenting the observables and the experimental constraints that can be set on inflationary models. The possibility of observing primordial gravitational wave (GW) produced during inflation is discussed. We present the reasons to deftne a classification of inflationary models and introduce the [3-function formalism for inflation by explaining why in this framework we can naturally define a set of universality classes for inflationary models. Theoretical motivations to support the formulation of inflation in terms of this formalism are presented. Some generalized models of inflation are introduced and the extension of the (3-function formalism for inflation to these models is discussed. Finally we focus on the study of models where the (pseudo-scalar) inflaton is non-minimally coupled to some Abelian gauge fields that can be present during inflation. The analysis of the problem is carried out by using a characterization of inflationary models in terms of their asymptotic behavior. A wide set of theoretical aspects and of observational consequences is discussed.

Thesis (M.Sc. (Physics))--North-West University, Potchefstroom Campus, 2008.

Thesis (Ph. D.)--University of Hong Kong, 1983.

Paper presented before the Second Pan American Scientific Congress, Washington, U.S.A., December 27, 1915-Janunary 8, 1916.

The existence of a Fisk-type heliospheric magnetic field (HMF) is one of the most debated questions in cosmic-ray modulation. Recently, Burger and Hitge [2004] developed a divergence-free Fisk-Parker hybrid magnetic field model to demonstrate the behaviour of cosmic rays in the heliosphere due to such a field. This approach has been refined and the properties of the consequent field are investigated. It is found that randomly directed magnetic field diffusion in and above the photosphere significantly influences the solar magnetic field both at the solar poles and near the polar coronal hole boundary. The solar cycle dependence of this field is investigated, a study which is of particular importance for studies of the long-term behaviour of cosmic rays, such as those undertaken at the SANAE base in Antarctica. The amplitudes of the 26-day recurrent cosmic-ray variations are modelled as function of both latitudinal gradient and heliolatitude and are found to agree qualitatively and in some cases quantitatively with the observational results reported by Zhang 119971 and Paizis et al. 119991. Although magnetic field data do not clearly indicate the existence of the Fisk field [see, e.g., Fursyth et al., 20021, this study supports the existence of a Fisk-type HMF. / Thesis (M.Sc. (Physics))--North-West University, Potchefstroom Campus, 2006.

Thesis (M.Sc. (Physics))--North-West University, Potchefstroom Campus, 2008.

Thesis (M.Sc. (Physics))--North-West University, Potchefstroom Campus, 2008.

Thesis (Ph.D.)--Tufts University, 2002. / Adviser: Alexander Vilenkin. Submitted to the Dept. of Physics. Includes bibliographical references (leaves 95-98). Access restricted to members of the Tufts University community. Also available via the World Wide Web;

Thesis (Ph. D.)--University of Washington, 2002. / Vita. Includes bibliographical references (p. 71-76).

Introdução: Os ligamentos denteados são extensões da pia-máter em cada lado da medula espinhal, totalizando cerca de 20 a 21 pares de estruturas fibrosas que se conectam com a dura-máter, ancorando a medula espinhal. Esses ligamentos são importantes referências anatômicas para cirurgias envolvendo estruturas no interior do canal vertebral e, portanto, muito bem conhecidos por cirurgiões que abordam o canal vertebral. No entanto, não encontramos a descrição deste ligamento em estudos de ressonância magnética (RM). Objetivo: Nosso objetivo foi avaliar a detecção dos ligamentos denteados na coluna cervical por meio de imagens de RM em sequências de aquisição volumétrica e com alta resolução espacial, e comparar a frequência de detecção desses ligamentos nos equipamentos de 1,5 Tesla e 3,0 Tesla. Resultados: Foram avaliados 116 exames de ressonância magnética da coluna cervical, sendo observada alta frequência de detecção dos ligamentos denteados na coluna cervical utilizando sequência volumétrica 3D COSMIC, tanto no equipamento de 1,5 Tesla quanto no equipamento de 3,0 Tesla. Não houve diferença estatisticamente significativa quando comparamos a frequência de detecção dos ligamentos entre os equipamentos de RM de 1,5T e 3,0 T. / Introduction: Denticulate ligaments are extensions of the pia mater on each side of the spinal cord, totaling about 20 to 21 pairs of fibrous structures that connect with the dura mater, anchoring the spinal cord. These ligaments are important anatomical references for surgeries involving structures inside the spinal canal and therefore well known to surgeons who approach the spinal canal. To our knowledge, there is no previous study on the feasibility to detect the denticulate ligaments using MRI. Objective: Our aim was to evaluate the detection of denticulate ligaments in the cervical spine using high resolution magnetic resonance imaging (MRI), and to compare the frequency of detection of these ligaments in 1.5 Tesla and 3.0 Tesla equipment. Results: We evaluated 116 MRI scans of the cervical spine and observed high frequency of detection of the denticulate ligaments in the cervical spine using the volumetric sequence 3D COSMIC on both the 1,5 Tesla and 3,0 Tesla MR equipments. There was no statistically significant difference in the frequency of detection of the ligaments between the MRI equipments.