Made available in DSpace on 2016-01-13T13:27:58Z (GMT). No. of bitstreams: 0 Previous issue date: 1992. Added 1 bitstream(s) on 2016-01-13T13:31:44Z : No. of bitstreams: 1 000854575.pdf: 1847934 bytes, checksum: 4588fc1d9a76f130849362a2f86a1b3a (MD5) / Analisamos neste trabalho ambos os modelos de gravitação induzida, pura e acoplada à matéria, a partir de dois pontos de vista: uma análise clássica e quântica independente de gauge para o modelo puro e uma análise clássica via espaço de fase reduzido para ambos modelos, introduzindo vínculos fixadores de gauge que dependem explicitamente do tempo / We analyze in this work two dimensional induced gravity both pure and coupled to matter fields along two approaches; quantum and classical gauge independent analysis for the pure model and a classical study via reduced phase space for both models, introducing gauge fixing constraints which depend explicitly on time

Orientador: Maria Cristina Batoni Abdalla / Coorientador: Elcio Abdalla / Resumo: Analisamos neste trabalho ambos os modelos de gravitação induzida, pura e acoplada à matéria, a partir de dois pontos de vista: uma análise clássica e quântica independente de gauge para o modelo puro e uma análise clássica via espaço de fase reduzido para ambos modelos, introduzindo vínculos fixadores de gauge que dependem explicitamente do tempo / Abstract:We analyze in this work two dimensional induced gravity both pure and coupled to matter fields along two approaches; quantum and classical gauge independent analysis for the pure model and a classical study via reduced phase space for both models, introducing gauge fixing constraints which depend explicitly on time / Doutor

Orientador: José Geraldo Pereira / Coorientador: Cássius A. Miquele de Melo / Banca: José Wadih Maluf / Banca: Ruben Aldrovandi / Resumo: No presente trabalho, faremos um estudo de algumas propriedades da versão teleparalela da relatividade geral. No primeiro capítulo, estudaremos diferentes maneiras de obter sua Lagrangiana. No segundo, faremos uma introdução à dinâmica de sistemas vinculados, e no terceiro estudaremos a formulação ADM do teleparalelismo, obtendo a álgebra dos vínculos. Por fim, estudaremos o equivalente às variáveis de Ashtekar teleparalelas / Abstract: In the present work we study some properties of the teleparallel equivalent of general relativity. In the first chapter, we analyse different ways to obtain the teleparallel Lagrangian. In the second, we make an introduction to the dynamics of constrained systems, and in the third we study the ADM formulation of teleparallel gravity, obtaining its constraint algebra. Finally, we make an analysis of the teleparallel equivalent to the Ashtekar variables / Mestre

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Despite the success of general relativity in explaining classical gravitational phenomena, several problems at the interface between gravitation and high energy physics remain open to date. The purpose of this thesis is to explore classical and quantum gravity in order to improve our understanding of different aspects of gravity, such as dark matter, gravitational waves and ination. We focus on the class of higher derivative gravity theories as they naturally arise after the quantization of general relativity in the framework of effective field theory. The inclusion of higher order curvature invariants to the action always come in the form of new degrees of freedom. From this perspective, we introduce a new formalism to classify gravitational theories based on their degrees of freedom and, in light of this classification, we argue that dark matter is no different from modified gravity. Additional degrees of freedom appearing in the quantum gravitational action also affect the behaviour of gravitational waves. We show that gravitational waves are damped due to quantum degrees of freedom and we investigate the backreaction of these modes. The implications for gravitational wave events, such as the ones recently observed by the Advanced LIGO collaboration, are also discussed. The early universe can also be studied in this framework. We show how ination can be accommodated in this formalism via the generation of the Ricci scalar squared, which is triggered by quantum effects due to the non-minimal coupling of the Higgs boson to gravity, avoiding instability issues associated with Higgs ination. We argue that the non-minimal coupling of the Higgs to the curvature could also solve the vacuum instability issue by producing a large effective mass for the Higgs, which quickly drives the Higgs field back to the electroweak vacuum during ination.

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