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Cette thèse s'intéresse à la cohomologie de fibrés en droite sur le fibré cotangent de variétés projectives. Plus précisément, pour $G$ un groupe algébrique simple, connexe et simplement connexe, $P$ un sous-groupe maximal de $G$ et $\omega$ un générateur dominant du groupe de caractères de $P$, on cherche à comprendre les groupes de cohomologie $H^i(T^*(G/P),\mathcal{L})$ où $\mathcal{L}$ est le faisceau des sections d'un fibré en droite sur $T^*(G/P)$. Sous certaines conditions, nous allons montrer qu'il existe un isomorphisme, à graduation près, entre $H^i(T^*(G/P),\mathcal{L})$ et $H^i(T^*(G/P),\mathcal{L}^{\vee})$ Après avoir travaillé dans un contexte théorique, nous nous intéresserons à certains sous-groupes paraboliques en lien avec les orbites nilpotentes. Dans ce cas, l'algèbre de Lie du radical unipotent de $P$, que nous noterons $\nLie$, a une structure d'espace vectoriel préhomogène. Nous pourrons alors déterminer quels cas vérifient les hypothèses nécessaires à la preuve de l'isomorphisme en montrant l'existence d'un $P$-covariant $f$ dans $\comp[\nLie]$ et en étudiant ses propriétés. Nous nous intéresserons ensuite aux singularités de la variété affine $V(f)$. Nous serons en mesure de montrer que sa normalisation est à singularités rationnelles. / In this thesis, we study the cohomology of line bundles on cotangent bundle of projective varieties. To be more precise, let $G$ be an semisimple algebraic group which is simply connected, $P$ a maximal subgroup and $\omega$ a dominant weight that generates the character group of $P$. Our goal is to understand the cohomology groups $H^i(T^*(G/P),\mathcal{L})$ where $\mathcal{L}$ is the sheaf of sections of a line bundle on $T^*(G/P)$. Under some conditions, we will show that there exists an isomorphism, up to grading, between $H^i(T^*(G/P),\mathcal{L})$ and $H^i(T^*(G/P),\mathcal{L}^{\vee})$. After we worked in a theoretical setting, we will focus on maximal parabolic subgroups related to nilpotent varieties. In this case, the Lie algebra of the unipotent radical of $P$ has a structure of prehomogeneous vector spaces. We will be able to determine which cases verify the hypothesis of the isomorphism by showing the existence of a $P$-covariant $f$ in $\comp[\nLie]$ and by studying its properties. We will be interested by the singularities of the affine variety $V(f)$. We will show that the normalisation of $V(f)$ has rational singularities.

Submitted by ANA KARLA PEREIRA RODRIGUES (anakarla_@hotmail.com) on 2017-08-11T16:01:13Z No. of bitstreams: 1 arquivototal.pdf: 1341956 bytes, checksum: 725d00067ec252af7f139395f2803b1b (MD5) / Made available in DSpace on 2017-08-11T16:01:13Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 1341956 bytes, checksum: 725d00067ec252af7f139395f2803b1b (MD5) Previous issue date: 2015-12-15 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / This work develops the theories of local cohomology and local homology with respect to an arbitrary set of ideals and generalises most of the important results from the classical theories. It also introduces the category of quasi-holonomic D-modules and proves some finiteness properties of local cohomology modules which generalise Lyubeznik's results in some sense. / Este trabalho desenvolve as teorias de cohomologia e homologia locais com respeito a um conjunto arbitrário de ideais e generaliza vários dos resultados importantes das teorias clássicas. Também, introduz a categoria dos D-módulos quase-holônomos e prova alguns resultados de finitude de cohomologia local que generalizam, em algum sentido, os resultados de G. Lyubeznik.

Made available in DSpace on 2014-07-29T16:02:20Z (GMT). No. of bitstreams: 1 Dissertacao Flavio P Vieira.pdf: 631827 bytes, checksum: b4c3dfd45d41b0313e21e87b61f0c94e (MD5) Previous issue date: 2012-04-12 / The main goal of this work is to establish a primary bound for the dimension of the second homology group of a group G, with coefficients in a field k of characteristic p, H2(G;k), using the operating system GAP. It will be presented with several examples, where in some cases, will be calculated the exact dimensions and in other cases only an upper bound. / O trabalho tem por objetivo principal estabelecer uma cota superior para a dimensão do segundo grupo de homologia de um grupo G, com coeficientes em um corpo k de característica p, H2(G;k), usando o sistema operacional GAP. Será apresentado uma gama de exemplos, onde em alguns casos, calcularemos exatamente a dimensão e em outras somente uma cota superior.

Dado um grupo G, a definição dos grupos de cohomologia com coeficientes em um ZG-módulo M podem ser dadas usando as técnicas usuais da Álgebra Homológica, que garantem a existência de resoluções projetivas P de Z como um ZG-módulo trivial, a equivalência entre resoluções distintas etc. Podemos também construir o produto cup em cohomologia, cuja definição depende de uma aproximação da diagonal para a resolução projetiva P. Entretanto, o cálculo explicito de tais resoluções e dos grupos de cohomologia pode ser bastante difícil na prática, e ainda mais difícil a obtenção de uma aproximação da diagonal. Nesta tese, obteremos resoluções livres e aproximações da diagonal para os grupos fundamentais das superfícies que são espaços K(G,1) e também para o grupo fundamental de fibrados do toro com base S^1, bem como a estrutura de anel de cohomologia de tais grupos. Ainda, para certos grupos virtualmente cíclicos G, obteremos o anel de cohomologia calculando diretamente uma resolução livre e uma aproximação da diagonal, ou então usando a sequência espectral de Lyndon-Hochschild-Serre. A motivação para o estudo da primeira família de grupos vem do fato de representarem variedades de dimensão 2 e 3, e da segunda família por ser constituída de grupos que atuam em esferas de homotopia. / Given a group G, a definition for its cohomology groups with coefficients in a given ZG-module M can be given using the standard techniques of Homological Algebra, that ensure the existence of projective resolutions P of Z as a trivial ZG-module, the equivalence between two such resolutions etc . We can also construct the cup product, whose definition depends on a diagonal approximation for a given projective resolution P. However, the explicit computation of such resolutions and of the cohomology groups may be very hard in practice, and even worse may be the task of constructing a diagonal approximation. In this thesis, we obtain free resolutions and diagonal approximations for the fundamental groups of surfaces that are K(G,1) spaces and for the fundamental group of the torus bundle with the circle as the base space, as well as the structure of the cohomology ring of these groups. Also, for some virtually cyclic groups, we obtain the cohomology ring by an explicit computation of a free resolution and a diagonal approximation, or by the Lyndon-Hochschild-Serre spectral sequence. The motivation for the study of the first family of groups comes from the fact that such groups represent manifolds of dimension 2 and 3, and the groups of the second family act on homotopy spheres.

In 1970, Raoul Bott published The Periodicity Theorem for the Classical Groups and Some of Its Applications, in which he uses this famous result as a guideline to present some important areas and tools of Algebraic Topology. This dissertation aims to use the path Bott presented in his article as a guideline to address certain topics on Algebraic Topology. We start this incursion developing important tools used in Homotopy Theory such as spectral sequences and Eilenberg-MacLane spaces, exploring how they can be combined to aid in computation of homotopy groups. We then study important results of Morse Theory, a tool which was in the centre of Botts proof of the Periodicity Theorem. We also develop two extensions: Morse-Bott Theory, and the applications of such results to the loopspace of a manifold. We end by giving an introduction to generalised cohomology theories and K-Theory. / Em 1970, Raoul Bott publicou o artigo The Periodicity Theorem for the Classical Groups and Some of Its Applications no qual usava esse famoso resultado como um guia para apresentar importantes áreas e ferramentas da Topologia Algébrica. O presente trabalho usa o mesmo caminho traçado por Bott em seu artigo como roteiro para explorar tópicos importantes da Topologia Algébrica. Começamos esta incursão desenvolvendo ferramentas importantes da Teoria de Homotopia como sequências espectrais e espaços de Eilenberg-MacLane, explorando como estes podem ser combinados para auxiliar em cálculos de grupos de homotopia. Passamos então a estudar resultados importantes de Teoria de Morse, uma ferramenta que estava no centro da demonstração de Bott do Teorema da Periodicidade. Desenvolvemos ainda, duas extensões: Teoria de Morse-Bott e aplicações destes resultados ao espaço de laços de uma variedade. Terminamos com uma introdução a teorias de cohomologia generalizadas e K-Teoria.

In this thesis, we investigate supersymmetric quantum mechanics (SUSYQM) and its relation to index theorems and equivariant cohomology. We define some basic constructions on super vector spaces in order to set the language for the rest of the thesis. The path integral in quantum mechanics is reviewed together with some related calculational methods and we give a path integral expression for the Witten index. Thereafter, we discuss the structure of SUSYQM in general. One shows that the Witten index can be taken to be the difference in dimension of the bosonic and fermionic zero energy eigenspaces. In the subsequent section, we derive index theorems. The models investigated are the supersymmetric non-linear sigma models with one or two supercharges. The former produces the index theorem for the spin-complex and the latter the Chern-Gauss-Bonnet Theorem. We then generalise to the case when a group action (by a compact connected Lie group) is included and want to consider the orbit space as the underlying space, in which case equivariant cohomology is introduced. In particular, the Weil and Cartan models are investigated and SUSYQM Lagrangians are derived using the obtained differentials. The goal was to relate this to gauge quantum mechanics, which was unfortunately not successful. However, what was shown was that the Euler characteristics of a closed oriented manifold and its homotopy quotient by U(1)n coincide.

Dans cette thèse, on construit des systèmes d’Euler à partir des unités (conjecturales) de Stark et celles de Rubin-Stark d’un corps de nombres K, pour décrire l’idéal caractéristique du X-quotient du module d’Iwasawa standard X∞ pour certains caractères p-adiques irréductibles X. Ici X∞ est le groupe de Galois de la pro-p-extension abélienne non ramifiée maximale de K∞, où K∞ est une Zp-extension adéquate de K. Plus précisément, on démontre des résultats de divisibilité formulée par la conjecture principale de la théorie d’Iwasawa. Nos démonstrations reposent essentiellement sur la théorie des systèmes d’Euler. / In this thesis, we construct Euler systems coming from the (conjectural) Stark units and those of Rubin-Stark of a number field K, to describe the characteristic ideal of the X-quotient of the standard Iwasawa module X∞, for some p-adic irreducible characters X. Here X∞ is the Galois group of the maximal unramified abelian pro-p-extension of K∞, where K∞ is an adequate Zp-extension of K. Precisely, we demonstrate a divisibility results formulated by the main conjecture of Iwasawa theory. Our demonstrations essentially are based on the theory of Euler systems.

Soit G un groupe algébrique semi-simple sur un corps de caractéristique 0. Ce mémoire discute d'un théorème d'annulation de la cohomologie supérieure du faisceau D des opérateurs différentiels sur une variété de drapeaux de G. On démontre que si P est un sous-groupe parabolique de G, alors H^i(G/P,D)=0 pour tout i>0. On donne en fait trois preuves indépendantes de ce théorème. La première preuve est de Hesselink et n'est valide que dans le cas où le sous-groupe parabolique est un sous-groupe de Borel. Elle utilise un argument de suites spectrales et le théorème de Borel-Weil-Bott. La seconde preuve est de Kempf et n'est valide que dans le cas où le radical unipotent de P agit trivialement sur son algèbre de Lie. Elle n'utilise que le théorème de Borel-Weil-Bott. Enfin, la troisième preuve est attribuée à Elkik. Elle est valide pour tout sous-groupe parabolique mais utilise le théorème de Grauert-Riemenschneider. On présente aussi une construction détaillée du faisceau des opérateurs différentiels sur une variété. / Let G be a semisimple algebraic group on a field of characteristic 0. This thesis discusses a vanishing theorem for the higher cohomology of the sheaf D of differential operators on a flag variety of G. We show that if P is a parabolic subgroup of G, then H^i(G/P,D)=0 for all i>0. In fact, we give three independent proofs of this theorem. The first proof, due to Hesselink, only works if the parabolic subgroup P is a Borel subgroup. It uses a spectral sequence argument as well as the Borel-Weil-Bott theorem. The second proof, due to Kempf, only works if the unipotent radical of P acts trivially on its Lie algebra. It only uses the Borel-Weil-Bott theorem. Finally, the third proof, due to Elkik, is valid for any parabolic subgroup. However, it uses the Grauert-Riemenschneider theorem. We also present a detailled construction of the sheaf of differential operators on a variety.

Soit G un groupe algébrique linéaire complexe, simple, connexe et simplement connexe. Étant donné un sous-groupe parabolique P G et un idéal nilpotent n p, il existe un morphisme propre d’effondrement G x P n = Gn. Il se factorise en une variété affine et normale N := SpecC [G P n] que nous appelons variété nilpotente. Sous l’hypothèse que l’effondrement soit génériquement fini, nous décrivons le groupe des classes de diviseurs équivariants de N à l’aide de C[N]-modules réflexifs équivariants de rang 1. Un représentant de chaque classe peut être choisi comme les sections globales d’un fibré en droite sur G x P' n' où G x P' n' = Gn' est un effondrement possiblement distinct qui se factorise à travers la même variété nilpotente. Dans le cas où le groupe G est de type A ou dans le cas d’un effondrement provenant de certains diagrammes de Dynkin pondérés spécifiques, nous démontrons que les représentants proviennent de poids qui peuvent être choisis comme dominants. Dans ce cas, nous démontrons que si le module représente un élément torsion du groupe des classes, alors il est Cohen–Macaulay. Nous en déduisons un théorème d’annulation en cohomologie. / Let G be a simple, connected, simply connected complex linear algebraic group with parabolic subgroup P G and nilpotent ideal n p. The proper collapsing map G x P n = Gn factors through the normal affine variety N := SpecC [G x P n] which is called a nilpotent variety. Assuming the collapsing is generically finite, we describe the equivariant divisor class group of N using rank 1 reflexive equivariant C[N]-modules. A representative of each class may be chosen as global sections of a line bundle over G x P' n' where G x P' n' = Gn' is a possibly distinct collapsing that factors through the same nilpotent variety. Assuming either G is of type A or the collapsing comes from specific weighted Dynkin diagrams,we showthat each representative arise from a weight that may be chosen dominant. Moreover, if the module represents a torsion element within the class group, then it is Cohen– Macaulay and we deduce a cohomological vanishing theorem.