Submitted by Emanuel Varela Cardoso (emanuel.varela@ufcg.edu.br) on 2018-10-09T18:55:52Z No. of bitstreams: 1 ARTHUR GONÇALVES CAVALCANTI – DISSERTAÇÃO (PPGFísica) 2016.pdf: 845402 bytes, checksum: dbdfb2a26834c477a45e9e735fa670d3 (MD5) / Made available in DSpace on 2018-10-09T18:55:52Z (GMT). No. of bitstreams: 1 ARTHUR GONÇALVES CAVALCANTI – DISSERTAÇÃO (PPGFísica) 2016.pdf: 845402 bytes, checksum: dbdfb2a26834c477a45e9e735fa670d3 (MD5) Previous issue date: 2016-02 / Capes / A teoria da relatividade geral prevê soluções tipo buraco negro, as quais são caracterizadas pela existência de um horizonte de eventos. Como exemplo, podemos citar a métrica obtida por Bãnados-Teitelboim-Zanelli (BTZ), que é uma solução da gravitação em (2+1)- dimensões, em que se considera uma constante cosmológica negativa. Nos últimos anos, buracos negros não-comutativos têm sido investigados na literatura por muitos autores. Em particular, a métrica BTZ não-comutativa foi obtida considerando-se a equivalência, que existe em três dimensões, entre gravitação e a teoria de Chern-Simons, que e uma teoria quântica de campos topológica em três dimensões, e usando-se o mapeamento de Seiberg-Witter com a solução em (2+1)-dimensões. A presença de divergências na teoria quântica de campos leva a considerar a possibilidade de modificar o princípio da incerteza de Heisemberg, introduzindo uma escala de comprimento fundamental, e esta modificação geram correções nas propriedades termodinâmica de buracos negros. Um dos efeitos associados as soluções tipo buraco negro, independente da dimensão do espaço-tempo, e a emissão térmica (Radiação Hawking), a qual e vista como um processo de tunelamento devido as flutuações do vácuo que acontece na região próxima ao horizonte de eventos. Neste trabalho, com o objetivo de investigar as correções devido a não comutatividade e ao princípio da incerteza generalizado, consideramos a métrica BTZ não-comutativa. Para tanto, usamos o formalismo de tunelamento via método de Hamilton-Jacobi. / The general relativity theory predicts black hole type solutions, which are characterized by the existence of an event horizon. As an example, the metric obtained by Ba~nados- Teitelboim-Zanelli (BTZ), which is a soluton of the gravitation in (2 + 1)-dimensions in what is considered a negative cosmological constant. In recent years, noncommutative black holes have been investigated by many authors in the literature. In particular, the BTZ metric non-commutative was obtained considering the equivalent, which exists in three dimensions, between gravitation and Chern-Simons theory, which is a quantum theory topological elds in three dimensions, and using it mapping Seiberg-Witter with the solution of (2 + 1)-dimensions. The presence of divergences in quantum eld theory leads to consider the possibility of modifying the principle of Heisenberg uncertainty by introducing a fundamental length scale, and this modi cation generate corrections to the thermodynamic properties of black holes. One of the e ects associated with the black hole type solutions, regardless of the space-time dimension is the thermal emission (Hawking radiation), which is seen as a process of tunneling due to vacuum uctuations that happens in the region near the event horizon . In this work, in order to investigate the corrections due to noncommutativity and the principle of widespread uncertainty, we consider the metric BTZ noncommutative. For this, we use tunneling formalism via Hamilton-Jacobi method.

Cette thèse vise à investiguer des moyens d'optimiser les performances de l'imagerie à haut contraste dans l'optique et le proche infrarouge pour la détection d'exo-planètes. L'étude principale a été menée sur le contraste à faible séparation permettant l'imagerie d'exo-planètes dans leur zone habitable. Cette détection directe est rendue possible par le développement des futurs grands télescopes et de coronographes de plus en plus performants à faible séparation. L'approche retenue permet de créer une zone sombre à haut contraste grâce à la coronographie et au « wavefront shaping » (contrôle de l'amplitude et de la phase avec 2 miroirs déformables), mais qui est limité par les effets de propagation de Fresnel. Les résultats obtenus ont déterminé les limitations de configuration optique pour le « wavefront shaping ». Grâce à une approche semi-analytique soutenue par des simulations numériques et une approche Monte-Carlo, ces limitations ont été analysées et quantifiées pour extraire les configurations optimales. Les résultats ont été appliqués au banc SPEED dont l'objectif est d'optimiser et de tester le haut contraste à faible séparation. Une deuxième étude a été une contribution à une étude générale de stabilité, en traitant la stabilité temporelle comme un paramètre indispensable dans la conception en amont d'instrument haut contraste. Un travail préliminaire a été initié sur la stabilité des instruments de mesure eux-mêmes à travers l'étude thermique d'un système de métrologie. Enfin, un dernier volet a été une étude de simulation de performances d'un nouveau concept d'imagerie différentielle basé sur l'acquisition d'images réalisées avec différentes tailles de pupilles. / This thesis aims to optimize high-contrast imaging performance in visible and near infrared for exoplanet detection. The main study focuses on high-contrast at small separation, to image exoplanets in their habitable zone. This direct detection is achievable with the next Extremely Large Telescopes and with the development of coronagraph providing high performance at small separation. The approach adopted for this study creates a high-contrast region (a dark hole) with the combination of coronagraphy and wavefront shaping (wavefront control of both phase and amplitude with 2 deformable mirrors) but is limited by the Fresnel propagation of phase aberrations. The goal of this work is to define the wavefront shaping limitation in optical configuration (deformable mirrors location, component optical quality, beam diameter). A semi-analytic approach followed by a Monte-Carlo analysis of numerical end-to-end simulations is studied, resulting in the definition of the optimal configuration. Results are then applied to SPEED, a test bench to optimize and test high-contrast imaging at small separation with a segmented pupil. Another aspect of this thesis is a contribution to a stability study to treat the temporal stability as a crucial parameter in high-contrast imaging instrumentation, at the conception level. A preliminary work is initiated during the thesis to analyse the stability of the measuring instrument itself. A metrology tool and its thermal behaviour are thus studied. Finally, the last part of this thesis is a performance analysis of a new differential imaging technique, developed to improve high contrast with observations with different diaphragm sizes.