Orientador : Sueli Irene Rodrigues Costa / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Matematica, Estatistica e Computação Cientifica / Made available in DSpace on 2018-08-06T14:39:59Z (GMT). No. of bitstreams: 1 Siqueira_RogerioMonteirode_D.pdf: 1994309 bytes, checksum: 7735d63966bc2d9b5c84ccac989c3289 (MD5) Previous issue date: 2006 / Resumo: Códigos esféricos euclidianos com simetrias são órbitas finitas de grupos de matrizes ortogonais. Tais códigos são também conhecidos como códigos de grupo. Neste trabalho, os códigos de grupo comutativo em dimensão par são caracterizados sobre toros planos, subvariedades da esfera. Em particular, se o grupo de matrizes for cíclico, o código gerado está contido em um nó que se enrola em um tora. Se a dimensão for ímpar, todo código de grupo comutativo mora em anti-primas cujas bases estão contidas em dois toros planos. Tal caracterização permitiu a construção de limitantes para a cardinalidade destas constelações de pontos em termos da distância mínima destes códigos e da densidade de empacotamento de um reticulado associado. Utilizando o método de Biglieri e Elia, que procura o vetor inicial cujo respectivo código de grupo cíclico tem a melhor distância mínima, apresentamos também os melhores códigos de grupo cíclico em dimensão quatro até 100 pontos / Abstract: Euclidean spherical codes with symmetries are orbits of finite orthogonal matrix groups. These codes are also known as group codes. ln this work, the commutative group codes in even dimensions are viewed on flat tori, which are submanifolds of the sphere. Also, if the matrix group is cyclic, the generated code lies on a knot which wraps around a torus. If the dimension is odd, every commutative group code lies on an anti-prism whose bases are contained in two flat tori. This interpretation lead us to build upper bounds for the cardinality of these constellations involving their minimum distance and the packing density of an associated lattice. Using a method by Biglieri and Elia, which searchs the initial vector for a cyclic group in order to achieve the best minimum distance, we also present the best cyclic group codes in dimension four up to 100 points / Doutorado / Matematica / Doutor em Matemática

Made available in DSpace on 2014-07-29T16:02:22Z (GMT). No. of bitstreams: 1 dissertacao_adriana_cintra_matem.pdf: 756254 bytes, checksum: 768c9b84205b306b8b6b935d926878cf (MD5) Previous issue date: 2010-03-19 / In this work we classify the complete surfaces with constant Gaussian curvature into the H2×R and S2×R.We show that exists a unique complete surface, up to isometries, with positive constant Gaussian curvature into the H2×R, and greater than one, into the S2×R and that there is no complete surfaces with constant Gaussian curvature K(I) < &#8722;1 into the H2×R and S2×R. We prove that even if &#8722;1 &#8804; K(I) < 0 there are infinite complete surfaces into the H2 ×R with Gaussian curvature K(I) and with additional assumption we prove there is if &#8722;1 &#8804; K(I) < 0 and 0 < K(I) < 1 there is no exists complete surfaces into S2×R with Gaussian curvature K(I). These results were obtained by Aledo, Espinar and Gálvez and can be found in [1]. / Neste trabalho classificamos as superfícies completas, com curvatura Gaussiana constante, em H2 × R e S2 × R. Mostramos que existe uma única superfície completa, a menos de isometria, com curvatura Gaussiana constante positiva em H2 × R, maior que um, em S2 × R, e que não existe superfície completa com curvatura Gaussiana, K(I) < &#8722;1, em H2 × R e S2 × R. Provamos ainda que, se &#8722;1 &#8804; K(I) < 0, existem infinitas superfícies completas em H2×R com curvatura Gaussiana K(I) e, com hipóteses adicionais, provamos que, se &#8722;1 &#8804; K(I) < 0 e 0 < K(I) < 1, não existe superfície completa em S2 ×R com curvatura Gaussiana K(I). Estes resultados foram obtidos por Aledo, Espinar e Gálvez e podem ser encontrados em [1].

What is in common between the Kepler problem, a Hydrogen atom and a rotating black- hole? These systems are described by different physical theories, but much information about them can be obtained by separating an appropriate Hamilton-Jacobi equation. The separation of variables of the Hamilton-Jacobi equation is an old but still powerful tool for obtaining exact solutions. The goal of this thesis is to present the theory and application of a certain type of conformal Killing tensor (hereafter called concircular tensor) to the separation of variables problem. The application is to spaces of constant curvature, with special attention to spaces with Euclidean and Lorentzian signatures. The theory includes the general applicability of concircular tensors to the separation of variables problem and the application of warped products to studying Killing tensors in general and separable coordinates in particular. Our first main result shows how to use these tensors to construct a special class of separable coordinates (hereafter called Kalnins-Eisenhart-Miller (KEM) coordinates) on a given space. Conversely, the second result generalizes the Kalnins-Miller classification to show that any orthogonal separable coordinates in a space of constant curvature are KEM coordinates. A closely related recursive algorithm is defined which allows one to intrinsically (coordinate independently) search for KEM coordinates which separate a given (natural) Hamilton-Jacobi equation. This algorithm is exhaustive in spaces of constant curvature. Finally, sufficient details are worked out, so that one can apply these procedures in spaces of constant curvature using only (linear) algebraic operations. As an example, we apply the theory to study the separability of the Calogero-Moser system.

Dans cette thèse, nous nous intéressons aux espaces temps dit globalement hyperboliques Cauchy compacts. Ce sont des espaces temps qui admettent une fonction, dite fonction temps de Cauchy, propre qui croit strictement le long des courbes causales inextensibles. Les niveaux de telles fonctions sont des hypersurfaces de type espace appelées hypersurfaces de Cauchy. La donnée d'une fonction temps définit naturellement une famille à 1-paramètres d'espaces métriques. Notre but est d'étudier le comportement asymptomatique de ces familles d'espaces métriques Il y a deux cas de figure à considérer : le premier étant le comportement asymptomatique dans le passé ; le deuxième est celui du comportement asymptomatique dans le futur. Plus de conditions géométriques sur l'espace temps et les fonctions temps à considérer seront nécessaires / In this thesis we're interested in globally hyperbolic Cauchy compact space-times. These are space-times that possess a proper function, called Cauchy time function, which ist strictly increasing along inextensible causal curves. A Cauchy time function defines naturally a 1-parameter family of metric spaces. One asks the natural and important question of the asymptomatic behaviour of this family with respect to the time : when time goes to 0 and when it goes towards infinity. Of course additional geometric condition on the space-ime and the time function will be necessary for a more appropriate study

La théorie des spins élevés est le domaine de la physique théorique au centre de cette thèse. Le contexte général de la naissance de cette théorie est présentée dans l’introduction. La première partie est axée sur les ingrédients (méthode de Noether, fonctions génératrices et formalisme ambiant) permettant la construction de vertex cubiques entre un champ scalaire de matière et un champ de jauge de spin élevé dans un espace-temps à courbure constante à partir des courants conservés en espace-temps plat. Dans un second temps, nous préparons les éléments pour un futur test de la correspondance holographique à l’ordre cubique voire quartique en la constante de couplage. Plus précisément, nous révisons en détail le calcul de certains propagateurs, ce qui nous mène à calculer les fonctions à trois points impliquant deux scalaires. La dernière partie, bien que concernant toujours l’holographie des spins élevés, traite de la physique non-relativiste. Les symétries et les courants d’un gaz parfait/unitaire de Fermi y sont étudiés. Le lien entre physiques relativiste et non-relativiste est obtenue grâce à la réduction dimensionnelle de Bargmann. / The higher spin theory is the field of theoretical physics at the center of this thesis. The general context of the birth of this theory is presenting in the introduction. The first part focuses on the ingredients (Noether method, generating functions and ambient formalism) for the construction of cubic vertices between a scalar matter field and a higher spin gauge field in a constant curvature space-time from conserved currents in flat space-time. In a second step, we prepare the around for a future test of the holographic correspondence in the cubic or quartic order in the coupling constant. More specifically, we review in detail the computation of some propagators, which leads us to calculate three-point functions involving two scalars. The last part, although always on the higher spin holography, deals with non-relativistic physics. Symmetries and currents of an ideal or unitary Fermi gas are studied. The link between relativistic and non-relativistic physics is obtained by Bargmann dimensional reduction.

Made available in DSpace on 2014-07-29T16:02:18Z (GMT). No. of bitstreams: 1 Dissertacao Lidiane Mayumi Hieda.pdf: 465165 bytes, checksum: a5ce3ff47770899f6a4edcca3e40ed69 (MD5) Previous issue date: 2011-05-13 / This work was based on papers On Compact Minimal Surfaces with non-negative Gaussian Curvature in a Space of Constant Curvature: I and Minimal Surfaces with Constant Curvature in 4-dimensional Space Forms, by Katsuei Kenmotsu, consisting in the classification of minimal surfaces with constant Gaussian curvature K in a 4-dimensional space form without any global assumption. We will show that an isometric minimal immersion x: M2(K) &#8594; M4(c), where c is sectional curvature, is either totally geodesic, or locally Clifford Torus, or locally a Veronese surface. As a corollary, we have that there is not isometric minimal immersions with constant negative Gaussian curvature into unit sphere S4(1) even locally. / Este trabalho foi baseado nos artigos On CompactMinimal Surfaces with non-negative Gaussian Curvature in a Space of Constant Curvature: I e Minimal Surfaces with Constant Curvature in 4-dimensional Space Forms de Katsuei Kenmotsu que consistem em classificar superfícies mínimas com curvatura Gaussiana constante K nas formas espaciais 4-dimensionais, sem alguma hipótese global. Mostraremos que uma imersão isométrica mínima x : M2(K) &#8594; M4(c), onde c é a curvatura seccional, ou é totalmente geodésica, ou localmente um Toro de Clifford, ou localmente uma superfície de Veronese. Como corolário, temos que não existe uma imersão isométrica mínima com curvatura Gaussiana constante negativa numa esfera unitária S4(1) mesmo que localmente.