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Various properties of linear infinite-dimensional Hamiltonian systems are studied. The structural stability of the Vlasov-Poisson equation linearized around a homogeneous stable equilibrium [mathematical symbol] is investigated in a Banach space setting. It is found that when perturbations of [mathematical symbols] are allowed to live in the space [mathematical symbols], every equilibrium is structurally unstable. When perturbations are restricted to area preserving rearrangements of [mathematical symbol], structural stability exists if and only if there is negative signature in the continuous spectrum. This analogizes Krein's theorem for linear finite-dimensional Hamiltonian systems. The techniques used to prove this theorem are applied to other aspects of the linearized Vlasov-Poisson equation, in particular the energy of discrete modes which are embedded within the continuous spectrum. In the second part, an integral transformation that exactly diagonalizes the Caldeira-Leggett model is presented. The resulting form of the Hamiltonian, derived using canonical transformations, is shown to be identical to that of the linearized Vlasov-Poisson equation. The damping mechanism in the Caldeira-Leggett model is identified with the Landau damping of a plasma. The correspondence between the two systems suggests the presence of an echo effect in the Caldeira-Leggett model. Generalizations of the Caldeira-Leggett model with negative energy are studied and interpreted in the context of Krein's theorem. / text

Orientador: Diego Sebastian Ledesma / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Matemática Estatística e Computação Científica / Made available in DSpace on 2018-08-27T09:00:29Z (GMT). No. of bitstreams: 1 Melo_MateusMoreirade_M.pdf: 1155879 bytes, checksum: 5582968247f7c4155e31b28d1531679a (MD5) Previous issue date: 2015 / Resumo: Neste trabalho, estudamos o conceito de estabilidade para folheações. Com este objetivo, usamos um complexo não-linear formado por mapas e variedades na categoria Fréchet Tame. Aplicamos uma variação do Teorema da Função Inversa de Nash-Moser ao complexo não-linear obtendo uma relação entre estabilidade e a exatidão tame da linearização do complexo não-linear. Além disso, o complexo linearizado é identificado com um trecho do complexo de Rham da folheação, ou seja, transforma-se o estudo de estabilidade em analisar a exatidão tame de um grupo de cohomologia da folheação. Assim descrevemos uma família de folheações estáveis, chamadas folheações infinitesimalmente estáveis. Esta família dá uma direção para o estudo de estabilidade de folheações / Abstract: In this work, we study the concept of stability for foliations. With this aim we use a non linear complex formed by maps and manifolds in Fréchet Tame category. We apply a variation of The Nash-Moser Inverse Function Theorem to non-linear complex obtaining a relation between the stability and the tame exactness of the linearized complex. Moreover, the linearized complex is identified with a piece of the complex de Rham of the foliation, i.e., we transformed the stability study into a analysis of tameness vanishing on the cohomology group of the foliation. Thus we describe a family of stable foliations, called infinitesimally stable foliations. This family gives a direction for the study of stability of foliations / Mestrado / Matematica / Mestre em Matemática