Thesis (Ph. D.)--University of Wisconsin--Madison, 1969. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (Ph. D.)--University of Texas at Austin, 2005. / Supervisor: Duane A. Dicus. Vita. Includes bibliographical references.

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

During inflation quantum fluctuations of the field driving inflation, known as inflaton, were stretched by inflationary expansion to galactic size scales or even larger. A possible implication of inflation -- if it is correct -- is that our observable universe was once of sub-Planckian size. Thus inflation could act as a magnifier to probe the short distance structure of space-time. General arguments about the quantum theory of gravity suggest that the short distance structure of space-time can be modeled as arising from some corrections to the well-known uncertainty relation between the position and momentum operators. Such modifications have been predicted by more fundamental theories such as string theory. This modified commutation relation has been implemented at the first quantized level to the theory of cosmological perturbations. In this thesis, we will show that the aforementioned scenario of implementing the minimal length to the action has an ambiguity: total time derivatives that in continuous space-time could be neglected and do not contribute to the equations of motion, cease to remain total time derivatives as we implement minimal length. Such an ambiguity opens up the possibility for trans-Planckian physics to leave an imprint on the ratio of tensor to scalar fluctuations. In near de-Sitter space, we obtain the explicit dependence of the tensor/scalar on the minimal length. Also the first consistency relation is examined in a power-law background, where it is found that despite the ambiguity that exists in choosing the action, Planck scale physics modifies the consistency relation considerably as it leads to large oscillations in the scalar spectral index in the observable range of scales. In the second part of the thesis, I demonstrate how the assumption of existence of invariant minimal length can assist us to explain the origin of cosmic magnetic fields. The third part of the thesis is dedicated to the study of signatures of M-theory Cascade inflation.

During inflation quantum fluctuations of the field driving inflation, known as inflaton, were stretched by inflationary expansion to galactic size scales or even larger. A possible implication of inflation -- if it is correct -- is that our observable universe was once of sub-Planckian size. Thus inflation could act as a magnifier to probe the short distance structure of space-time. General arguments about the quantum theory of gravity suggest that the short distance structure of space-time can be modeled as arising from some corrections to the well-known uncertainty relation between the position and momentum operators. Such modifications have been predicted by more fundamental theories such as string theory. This modified commutation relation has been implemented at the first quantized level to the theory of cosmological perturbations. In this thesis, we will show that the aforementioned scenario of implementing the minimal length to the action has an ambiguity: total time derivatives that in continuous space-time could be neglected and do not contribute to the equations of motion, cease to remain total time derivatives as we implement minimal length. Such an ambiguity opens up the possibility for trans-Planckian physics to leave an imprint on the ratio of tensor to scalar fluctuations. In near de-Sitter space, we obtain the explicit dependence of the tensor/scalar on the minimal length. Also the first consistency relation is examined in a power-law background, where it is found that despite the ambiguity that exists in choosing the action, Planck scale physics modifies the consistency relation considerably as it leads to large oscillations in the scalar spectral index in the observable range of scales. In the second part of the thesis, I demonstrate how the assumption of existence of invariant minimal length can assist us to explain the origin of cosmic magnetic fields. The third part of the thesis is dedicated to the study of signatures of M-theory Cascade inflation.

Several previous studies, including one using early Sanae radar data, have found examples of high speed ionospheric plasma flows on the nightside, mapping to the magnetospheric tail, during periods which were magnetically quiet. These high speed flows were interpreted to be associated with the release of energy from a rapid reconfiguration of tail magnetic field lines due to reconnection. Such events are now known as ‘TRINNIs’ or ‘tail reconnection during IMF northward, non-substorm intervals’. The purpose of this study was to identify further TRINNI events, using SuperDARN data from both hemispheres. In situations where the y-component of the Interplanetary Magnetic Field dominates over the z-component, the directions of both the high speed flows and the underlying convection pattern depend on the direction of the y-component. Some examples of likely TRINNI events for cases where the y-component was positive and negative are presented and discussed. The assumption of a non-substorm interval is justified by magnetometer and GOES satellite data, and the observations are discussed in relation to magnetic reconnection in the magnetotail. / Thesis (M.Sc.)-University of KwaZulu-Natal, Westville, 2010.

Orientador: Ernesto Kemp / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Física Gleb Wataghin / Made available in DSpace on 2018-08-25T18:38:19Z (GMT). No. of bitstreams: 1 Silva_MarceloZimbres_D.pdf: 8568193 bytes, checksum: 2348942e48cd0c1c610715988bd1d2f6 (MD5) Previous issue date: 2014 / Resumo: Devido à ação do campo magnético cósmico, trajetórias de raios cósmicos provenientes de uma mesma fonte podem ser defletidas e dar origem a estruturas filamentares cujos eventos são ordenados de acordo com suas energias, os multipletos. Nesse trabalho, propomos um novo método para identificação de multipletos, baseado no uso de uma classe de funções definidas sobre a esfera, chamadas de wavelets esféricos. Para testar o método aplicamos a análise em dados simulados. Primeiramente usamos um fundo isotrópico, onde um multipleto pode ocorrer apenas ao acaso. Posteriormente fazemos a análise colocando um multipleto em uma posição aleatória no mesmo fundo isotrópico. Com isso calculamos erros de tipo I e II. O método também é aplicado em dados obtidos pelo Observatório Pierre Auger para eventos com energia E > 15 x10^{18}eV / Abstract: Due to the action of the intervening cosmic magnetic fields, the trajectories of ultra-high energy cosmic rays (UHECRs) can be deflected in such a way as to create clustered energy-ordered filamentary structures in the arrival directions of these particles, the so-called multiplets. In this work we propose a new method based on the spherical wavelet transform to identify multiplets in sky maps containing arrival directions of UHECRs. The method is illustrated in simulations with a multiplet embedded in isotropic backgrounds with different numbers of events, and on data from the Pierre Auger Observatory. The efficiency of the algorithm is assessed through the calculation of Type I and II erros / Doutorado / Física / Doutor em Ciências

Thesis. 1977. M.S.--Massachusetts Institute of Technology. Dept. of Earth and Planetary Sciences. / Microfiche copy available in Archives and Science. / Bibliography : leaves 72-73. / M.S.

Orientador: Ernesto Kemp / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Física Gleb Wataghin / Made available in DSpace on 2018-08-20T15:39:35Z (GMT). No. of bitstreams: 1 Batista_RafaelAlves_M.pdf: 8040703 bytes, checksum: 596e886c4828986af7fb003ba71adf9b (MD5) Previous issue date: 2012 / Resumo: Campos magnéticos cósmicos são ubíquos e estão presentes em todas as escalas, desde os planetas até os superaglomerados de galáxias. Sabe-se que o campo magnético da Via Láctea possui uma componente regular, que tem uma estrutura espiral, e uma componente aleatória. Muitas questões acerca do magnetismo galáctico ainda permanecem sem respostas, e o modelo de espiral mais adequado para descrever as observações é incógnito. Uma possibilidade pouco explorada para estudar o campo magnético da Via Láctea é utilização de informações relacionadas à propagação de partículas carregadas através da mesma. Neste contexto estão inseridos os raios cósmicos ultra-energéticos, as partículas mais energéticas do universo, cuja origem, composição química e mecanismos de aceleração e propagação não são bem compreendidos. A deflexão de partículas provenientes da mesma fonte no campo magnético galáctico pode gerar estruturas filamentares com eventos ordenados por energia, os chamados multipletos, sendo esta uma assinatura única deixada pelo campo em mapas contendo direções de chegada de raios cósmicos. Neste trabalho é apresentado um método inédito para estudos do campo magnético galáctico, através da identificação e análise da orientação de multipletos nestes mapas. Este método baseia-se na transformada de wavelets na esfera, que permite amplificar a razão sinal-ruído e fazer reconhecimento de padrões, de forma a identificar multipletos imersos em ruído de natureza estocástica. Na primeira parte do trabalho o método foi aplicado a dados simulados visando obter a orientação esperada para multipletos oriundos de fontes em diversas partes da esfera celeste, segundo diferentes modelos de campo magnético galáctico. Na segunda parte do trabalho, aplicou-se o método a eventos detectados pelo Observatório de Raios Cósmicos Pierre Auger. A confrontação dos resultados de dados reais e simulações permite restringir modelos de campo magnético galáctico / Abstract: Cosmic magnetic fields are ubiquitous and are present in all size scales, from planets to superclusters of galaxies. The magnetic field of the Milky Way has a regular component, with a spiral structure, and a random component. Many questions concerning galactic magnetism still remain unanswered, and the spiral model which best fits the observations is unknown. An underexplored possibility to probe these fields is to use information related to the propagation of charged particles through them. In this context, an interesting probe are the ultrahigh energy cosmic rays, the most energetic particles in the universe, whose origin, chemical composition and mechanisms of acceleration and propagation are not well-understood. The deflection of particles coming from the same source can generate threadlike structures with events ordered by energy, the so-called multiplets, which imprints a unique signature of the galactic magnetic field in maps containing arrival directions of cosmic rays. In the present work it is presented a novel method to probe the galactic magnetic field, by identifying and analysing the orientation of multiplets in these maps. This method relies on the spherical wavelet transform, which is capable of amplifying the signal-to-noise ratio and perform pattern matching, so that it is possible to identify multiplets embedded in a stochastic background. In the first part of this work the method is applied to simulated data, aiming to obtain the expected orientations for multiplets associated to sources in several regions of the celestial sphere, according to different models of galactic magnetic field. In the second part of the work the method was applied to events detected by the Pierre Auger Observatory. A confrontation between the results using real and simulated data allows one to impose constraints to galactic magnetic field models / Mestrado / Física / Mestre em Física