Cette thèse porte sur quelques inégalités de type Trudinger-Moser et leurs applications à l'étude des injections de Sobolev qu'elles induisent dans les espaces d'Orlicz et à l'analyse d'équations aux dérivées partielles non linéaires à croissance exponentielle.Le travail qu'on présente ici se compose de trois parties. La première partie est consacrée à la description du défaut de compacité de l'injection de Sobolev 4D dans l'espace d'Orlicz dansle cadre radial.L'objectif de la deuxième partie est double. D'abord, on caractérise le défaut de compacité de l'injection de Sobolev 2D dans les différentes classes d'espaces d'Orlicz. Ensuite, on étudiel'équation de Klein-Gordon semi-linéaire avec non linéarité exponentielle, où la norme d'Orlicz joue un rôle crucial. En particulier, on aborde les questions d'existence globale, de complétude asymptotique et d'étude qualitative.Dans la troisième partie, on établit des inégalités optimales de type Adams, en étroite relation avec les inégalités de Hardy, puis on fournit une description du défaut de compacité des injections de Sobolev qu'elles induisent / This thesis focuses on some Trudinger-Moser type inequalities and their applications to the study of Sobolev embeddings they induce into the Orlicz spaces, and the investigation of nonlinear partial differential equations with exponential growth.The work presented here includes three parts. The first part is devoted to the description of the lack of compactness of the 4D Sobolev embedding into the Orlicz space in the radialframework.The aim of the second part is twofold. Firstly, we characterize the lack of compactness of the 2D Sobolev embedding into the different classes of Orlicz spaces. Secondly, we undertakethe study of the nonlinear Klein-Gordon equation with exponential growth, where the Orlicz norm plays a crucial role. In particular, issues of global existence, scattering and qualitativestudy are investigated.In the third part, we establish sharp Adams-type inequalities invoking Hardy inequalities, then we give a description of the lack of compactness of the Sobolev embeddings they induce

In this thesis uniform asymptotic approximations of integrals are discussed. In order to derive these approximations, two well-known methods are used i.e., the saddle point method and the Bleistein method. To start with this, examples are given to demonstrate these two methods and a general idea of how to approach these techniques. The asymptotics of the hypergeometric functions with large parameters are discussed i.e., 2F1 (a + e1λ, b + e2λ c + e3λ ; z)where ej = 0,±1, j = 1, 2, 3 as |λ|→ ∞, which are valid in large regions of the complex z-plane, where a, b and c are fixed. The saddle point method is applied where the saddle point gives a dominant contributions to the integral representations of the hypergeometric functions and Bleistein’s method is adopted to obtain the uniform asymptotic approximations of some cases where the coalescence takes place between the critical points of the integrals. As a special case, the uniform asymptotic approximation of the hypergeometric function where the third parameter is large, is obtained. A new method to estimate the remainder term in the Bleistein method is proposed which is created to deal with new type of integrals in which the usual methods for the remainder estimates fail. Finally, using the asymptotic property of the hypergeometric function when the third parameter is large, the uniform asymptotic approximation of the monic Meixner Sobolev polynomials Sn(x) as n → ∞ , is obtained in terms of Airy functions. The asymptotic approximations for the location of the zeros of these polynomials are also discussed. As a limit case, a new asymptotic approximation for the large zeros of the classical Meixner polynomials is provided.

L'objet de cette thèse est la résolution de problèmes elliptiques dans le demi-espace. En partant des problèmes déjà traités de Dirichlet et de Neumann pour l'opérateur de Laplace dans cette géométrie, nous avons exploré différents aspects du problème biharmonique et de celui de Stokes. Nous donnons des résultats fondamentaux d'existence, d'unicité et de régularité. Le cadre fonctionnel dans lequel nous nous plaçons est celui des espaces de Sobolev avec poids. Nous considérons ici des conditions aux limites non homogènes qu'on suppose également dans des espaces de Sobolev avec poids. Un aspect non négligeable de cette étude a trait aux conditions aux limites singulières et aux solutions très faibles qui en découlent. Il y est aussi abordé la question des conditions aux limites non standard, en particulier de type Navier pour le problème de Stokes.

Primary objective of the thesis is proof of the statement that if for ∈ ℕ a ≥ 1 a bilipschitz mapping belongs to +1, loc ∩ ,∞ loc then also its inverse −1 belongs to +1, loc . We prove a similar statement also for spaces loc . For this purpose we construct a new ordering of -th partial derivatives to generalized Jacobian matrix. Thanks to this matrix we are able to differentiate matrices in an applicable way. Generalized Jacobian matrix is projected so that there still holds the Chain rule and, in some way, also rules for matrices product differentiation. 1

In this thesis we present new ideas and mathematical insights in the field of Compton Scattering Tomography (CST), an X-ray and gamma ray imaging technique which uses Compton scattered data to reconstruct an electron density of the target. This is an area not considered extensively in the literature, with only two dimensional gamma ray (monochromatic source) CST problems being analysed thus far. The analytic treatment of the polychromatic source case is left untouched and while there are three dimensional acquisition geometries in CST which consider the reconstruction of gamma ray source intensities, an explicit three dimensional electron density reconstruction from Compton scatter data is yet to be obtained. Noting this gap in the literature, we aim to make new and significant advancements in CST, in particular in answering the questions of the three dimensional density reconstruction and polychromatic source problem. Specifically we provide novel and conclusive results on the stability and uniqueness properties of two and three dimensional inverse problems in CST through an analysis of a disc transform and a generalized spindle torus transform. In the final chapter of the thesis we give a novel analysis of the stability of a spindle torus transform from a microlocal perspective. The practical application of our inversion methods to fields in X-ray and gamma ray imaging are also assessed through simulation work.

Dissertação apresentada como requisito par- cial à obtenção do grau de Mestre em Matemática Aplicada, Programa de Pós- Graduação em Matemática Aplicada, Setor de Ciências Exatas, Universidade Federal do Paraná. Orientador: Prof. Dr. João Batista de Mendonça Xavier. 2008 / Submitted by Nilson Junior (nilson.junior@unila.edu.br) on 2016-05-24T17:53:40Z No. of bitstreams: 2 rodrigo_bloot.pdf: 429185 bytes, checksum: 76bb565aa88a1ed4d6e5640ad4f616e5 (MD5) Recibo Deposito Legal_Dissertacao_Rodrigo Bloot.pdf: 205693 bytes, checksum: ba27366b65e1dc7c227c973c8e74d413 (MD5) / Made available in DSpace on 2016-05-24T17:54:14Z (GMT). No. of bitstreams: 2 rodrigo_bloot.pdf: 429185 bytes, checksum: 76bb565aa88a1ed4d6e5640ad4f616e5 (MD5) Recibo Deposito Legal_Dissertacao_Rodrigo Bloot.pdf: 205693 bytes, checksum: ba27366b65e1dc7c227c973c8e74d413 (MD5) Previous issue date: 2008 / Este trabalho trata da solubilidade de problemas elípticos da forma < Lu = f (x; u; ru) em u = 0 sobre @ com um domínio limitado do R n e com fronteira suave. Primeiramente, seguindo [7], estudaremos o problema dado com L na forma Lu = nx i;j= @ @x i a ij (x) @u + @x j nx i= b i (x) @u @x i Para mostrar que este problema possui ao menos uma solução em W 2;p (), para p < n; usaremos o método de sub-supersolução. Posteriormente, guiados por [9], estudaremos o problema com L = Mostraremos que tal problema possui solução fraca, ou seja, em H o () Para isso usaremos métodos variacionais. Mas, antes de atacarmos os problemas faremos um aparato geral da teoria que está por trás destes resultados, como funções testes, teoria de distribuições, espaços de Sobolev, entre outros. A exposição destes conteúdos básicos não será longa, pois o intuito é apenas indicar o que é minimamente necessário para entender as técnicas que aqui serão expostas.

The method of steepest descent is applied to a nonlinearly constrained optimization problem which arises in the study of liquid crystals. Let Ω denote the region bounded by two coaxial cylinders of height 1 with the outer cylinder having radius 1 and the inner having radius ρ. The problem is to find a mapping, u, from Ω into R^3 which agrees with a given function v on the surfaces of the cylinders and minimizes the energy function over the set of functions in the Sobolev space H^(1,2)(Ω; R^3) having norm 1 almost everywhere. In the variational formulation, the norm 1 condition is emulated by a constraint function B. The direction of descent studied here is given by a projected gradient, called a B-gradient, which involves the projection of a Sobolev gradient onto the tangent space for B. A numerical implementation of the algorithm, the results of which agree with the theoretical results and which is independent of any strong properties of the domain, is described. In chapter 2, the Sobolev space setting and a significant projection in the theory of Sobolev gradients are discussed. The variational formulation is introduced in Chapter 3, where the issues of differentiability and existence of gradients are explored. A theorem relating the B-gradient to the theory of Lagrange multipliers is stated as well. Basic theorems regarding the continuous steepest descent given by the Sobolev and B-gradients are stated in Chapter 4, and conditions for convergence in the application to the liquid crystal problem are given as well. Finally, in Chapter 5, the algorithm is described and numerical results are examined.

Made available in DSpace on 2014-06-11T19:22:18Z (GMT). No. of bitstreams: 0 Previous issue date: 2012-02-27Bitstream added on 2014-06-13T19:48:19Z : No. of bitstreams: 1 tavares_ls_me_sjrp.pdf: 287773 bytes, checksum: 8f285f1d6d9bb5fc795a4aa2698728a8 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Nesse trabalho provamos existência de solução fraca para o problema de Dirichlet não linear { − ∆ u = f ( u ) + g em Ω, u = 0 em ∂ Ω. onde f ∈ C 2 ( R), g ∈ L2 (Ω) onde Ω é um domínio suave e limitado de R3 . Para isso estudamos alguns resultados básicos do Cálculo Diferencial em espaços de Banach e o problema de Dirichlet homogêneo para a equação de Laplace / In this work we prove the existence of weak solution for the nonlinear Dirichlet problem{ − ∆ u = f ( u ) + g em Ω, u = 0 em ∂ Ω. where f ∈ C 2 ( R ) , g ∈ L2 (Ω) and Ω is a b ounded smo oth domain in R3 . For this we study some basic results of the Differential Calculus in Banach spaces and the homogeneous Dirichlet problem for Laplace’s equation

CoordenaÃÃo de AperfeiÃoamento de Pessoal de NÃvel Superior / O objetivo desse trabalho à estudarmos a controlabilidade aproximada, via estratÃgia de Stackeberg-Nash, para equaÃÃo do calor em domÃnios ilimitados, bem como para equaÃÃo da onda e para fluidos micropolares em domÃnios com fronteira variÃvel . / The purpose of this work is study the approximate controllability, via Stackelberg-Nash strategies to heat equation in unlimited domains, as well to wave equation and for micropolars fluids in domains with moving boundary.

1°) Utilisation d'inégalités fonctionnelles de Bobkov pour l'établissement de principes de grandes déviations quasi-gaussiens. <br /><br />2°) Etude de l'inégalité de Sobolev logarithmique en théorie de l'information. <br /><br />3°) Etablissement d'inégalités de Poincaré et de Sobolev logarithmiques pour certaines dynamiques de Kawasaki et Glauber pour un modèle à spins continus en mécanique statistique.