Thesis (Ph.D.)--McMaster University (Canada), 1995. / Source: Dissertation Abstracts International, Volume: 57-03, Section: B, page: 1856. Adviser: R. E. Pudritz.

Thesis (Ph.D.) - University of Glasgow, 2008. / Ph.D. thesis submitted to the Department of Geographical and Earth Sciences, Faculty of Physical Sciences, University of Glasgow, 2008. Includes bibliographical references. Print version also available.

Academisch proefschrift--Amsterdam. / "Summary": p. 232-234. "Stellingen": [4] p. inserted. "Literatuurlijst": p. 235-240.

Thesis (Ph. D.)--University of Chicago, Department of Physics, March 2003. / Includes bibliographical references. Also available on the Internet.

Thesis (Ph. D.)--University of Chicago, Dept. of Astronomy and Astrophysics, Jun. 2003. / Includes bibliographical references (p. 168-171). Also available on the Internet.

Thesis (Ph. D.)--Ohio State University, 2006. / Title from first page of PDF file. Includes bibliographical references (p. 93-98).

Since the discovery of the cosmic microwave background (CMB), our understanding of the cosmos has been rapidly evolving. Detailed measurements of the CMB temperature fluctuations have led to a standard cosmological model, which traces the origin of the large-scale structure of the universe to quantum fluctuations during inflation. Although the basic framework of inflationary cosmology is now well-established, the microphysical mechanism responsible for the accelerated expansion remains a mystery. In this thesis, we describe how the physics underlying inflation can be probed using two cosmological observables: higher-order correlations of primordial density perturbations (non-Gaussianity) and primordial gravitational waves (tensor modes). In the first part of the thesis, we explore novel signatures of high-energy physics in higher- order correlation functions of inflationary perturbations. First, we use causality and unitarity to make connections between cosmological observations and the underlying short-distance dynamics of single-field inflation. We obtain a constraint on the size and the sign of the four-point function in terms of the amplitude of the three-point function. We then study the imprints of extra massive particles of arbitrary spin on the three-point function. We classify the couplings of these particles to inflationary scalar and tensor perturbations and derive explicit shape functions for their three- point functions that can serve as templates for future observational searches. Establishing the particle content during inflation would provide important hints for the microscopic theory of inflation. In the second part, we study ways of testing the nature of inflation using inflationary tensor modes. We consider effects of gravitational corrections to Einstein gravity in models of high-scale inflation. We show that these scenarios can lead to a violation of the tensor consistency condition (i.e. the relation between the amplitude and the scale-dependence of the tensor two-point function) that is satisfied by canonical single-field inflationary models. Finally, we consider the prospects for measuring the inflationary superhorizon signature in future observations. We define an estimator that captures superhorizon correlations and present forecasts for the detectability of the signal with future CMB polarization experiments.

Le rayonnement cosmique galactique nucléaire est composé de noyaux de différentes espèces et ses sources sont encore mal identifiées. Cette méconnaissance est en partie due au caractère diffusif de la propagation des noyaux dans les champs magnétiques dont la composante turbulente supprime toute information sur la position des sources. Dans le rayonnement cosmique, on distingue les noyaux pri- maires qui sont principalement créés puis accélérés près de leurs sources des noyaux secondaires, uniquement créés par spallation des primaires plus lourds. La mesure des rapports d'abondance se- condaire sur primaire permet d'étudier les processus de propagation et donc de remonter aux méca- nisme sources du rayonnement cosmique. Cette étude apporte de plus une meilleure compréhension de l'environnement astrophysique galactique. Ce travail nécessite une très bonne connaissance des sections efficaces d'interaction du rayonnement cosmique dans le milieu interstellaire qui régissent la modification des abondances lors de la propagation. La première partie de cette thèse est dédiée à la contrainte des paramètres de propagation du rayonnement cosmique galactique via l'étude des abondances des éléments du quartet (1H,2H,3He,4He). À partir d'une nouvelle estimation des sections efficaces, une analyse statistique a permis de démontrer le potentiel de ces éléments pour contraindre les modèles de propagation du rayonnement cosmique. Ces contraintes restent cependant limitées par la précision statistique des mesures actuelles et justifient la mise en œuvre de nouvelles expériences. La deuxième partie de cette thèse est dédiée à la mesure des abondances avec l'expérience CREAM, une expérience embarquée en ballon. Cette mesure nécessite l'identification des éléments dans le dé- tecteur, le calcul des efficacités des sous-détecteurs, la déconvolution des effets dus aux erreurs sur la mesure de l'énergie ainsi que la prise en compte des effets atmosphériques. Cette analyse des données du 3ième vol de CREAM a permis une estimation des abondances des éléments bore, carbone, azote et oxygène. / The sources of Galactic cosmic-ray (GCR) nuclei are still poorly identified. This is partly due to the diffusive propagation (in turbulent magnetic fields) that erases all directional information about the measured fluxes. The species that are predominantly created and accelerated in the sources are denoted 'primary species'. Those mostly created by spallation of heavier primary species are denoted 'secondary species'. While primary fluxes give access to the source parameters, secondary-to-primary ratios trace propagation processes. Key quantities for such studies are the fragmentation cross sections on the interstellar gas and the measured fluxes and ratios. In the first part of this thesis, we provide new constraints on the Galactic propagation parameters from the quartet elements (1H,2H,3He,4He), relying on a new estimate of their cross sections and an evolved statistical analysis. The derived constraints are competitive with those obtained from the standard B/C ratio analysis. The results are however limited by the precision of current measurements and motivate the development of new experiments. The second part of this thesis is dedicated to the analysis of cosmic-ray fluxes measured with the CREAM balloon-borne experiment. We present the particle identification in the detector, the estimation of efficiencies for each sub-detector, the energy reconstruction, and the atmospheric correction. Applied to the 3rd flight data (CREAM-III), we provide new data points for the boron, carbon, nitrogen and oxygen elements above 100 GeV/n.

Made available in DSpace on 2014-10-09T12:34:02Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:59:36Z (GMT). No. of bitstreams: 0 / Tese (Doutoramento) / IPEN/T / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

Orientador: Rogério Rosenfeld / Banca: Reuven Opher / Banca: Adriano Antônio Natale / Resumo: A origem dos raios cósmicos de altíssimas energias (RCAE's) é uma das maiores questões em aberto na astrofísica. Um dos modelos propostos para explicar estes eventos sugere que eles sejam produtos do decaimento de partículas metaestáveis supermassivas, as quais chamamos partículas X. Estas partículas, que seriam uma fração da matéria escura fria no Universo, podem ser produzidas no período de reaquecimento após a fase inflacionária no Universo primordial. Estudamos esta possibilidade e, a partir do fluxo detectado de RCAE's, obtivemos limites para alguns parâmetros como a meia vida e a razão de ramificação para o decaimento direto do inflaton em partículas X / Abstract: The origin of ultra high energy cosmic rays (UHECR's) is one of the major unresolved questions in astrophysics. One of the models proposed to explain these events suggests that they are the decay products of supermassive metastable particles, which we call X particles. These particles can be produced in the reheating period following the inflationary epoch of the early Universe and they would be a fraction of cold dark matter. We study this possibility and obtain constraints on some parameters such as the lifetime and branching ratio for the direct decay of the inflaton to X-particIes, from the requirement that they are responsible for the observed UHECR flux / Mestre