O objetivo desse trabalho é fazer uma enumeração dos fibrados planos reais sobre algumas superfícies, como por exemplo, a esfera e o g-toro. Entre outras ferramentas, utilizamos a co-homologia das superfícies, com coeficientes locais, e também o método desenvolvido por Larmore para contar classes de homotopia de levantamento de funções. / The aim of this work is enumerate the plane bundles over some surfaces, for example the sphere and the g-torus. Among other tools we used cohomology of the surfaces with local coefficients and also the method developed by Larmore to count homotopy classes of lifting of functions.

Neste trabalho, fazemos um estudo das correntes e das medidas transversas invariantes por holonomia, e mostraremos o resultado de D. Sullivan [23] sobre a correspondência biunívoca entre estes dois objetos. Em particular mostraremos um resultado conhecido de J. Plante [17] sobre a existência de medidas transversas invariantes sob a hipótese de crescimento sub-exponencial. Apresentamos também, o resultado devido a Ruelle-Sullivan [19] de que a medida de máxima entropia de um difeomorfismo topologicamente mixing pode-se expressar como o produto de duas medidas transversas invariantes para as folheações estáveis e instáveis. Por último, mostramos que os difeomorfismos de Anosov topologicamente mixing, que preservam a orientação das folhas estáveis e folhas instáveis induzem elementos da cohomologia de DeRham / In this work, we make a study of currents and holonomy invariant transverse measure, and we will show the result of D. Sullivan [23] about the biunivocal correspondence between these two objects. In particular we show a known result of J. Plante [17] about the existence of invariant transverse measures under the hypothesis of sub-exponential growth. Also we will present, the result due to Ruelle-Sullivan [19] that the maximum entropy measure of a diffeomorphism topologically mixing can be expressed as the product of two invariant transverse measures for stable and unstable foliations. Finally, we show that the Anosov diffeomorphisms topologically mixing, which preserve the orientation of the leaves stable and unstable induce elements DeRham cohomology

Blasius et Rogawski ont formulé une conjecture qui prévoit que l'action du Frobenius sur la cohomologie d'une variété de Shimura est annulée par un certain polynôme, à coefficients dans l'algèbre de Hecke. C'est l'analogue de la célèbre relation d'Eichler-Shimura pour la courbe modulaire. Dans cette thèse, on démontre cette conjecture pour les variétés de Shimura associées aux groupes unitaires en signature (n-1,1) quand n est impair. Par ailleurs, on étudie certains aspects dans le cas particulier n=3. On montre explicitement la relation de congruence sur le lieu ordinaire. De plus, on étudie le graphe des cristaux supersinguliers et les relèvements d'isogénies en caractéristique nulle. / Blasius and Rogawski have stated a conjecture saying that the action of the Frobenius element on the cohomology of a Shimura variety is annihilated by some polynomial with coefficients in the Hecke algebra. This is the analogue of the Eichler-Shimura congruence relation for the modular curve. In this thesis, we prove this conjecture for Shimura varieties associated to unitary groups in signature (n-1,1) when n is odd. We also investigate some particular aspects in the case n=3. We explicitely show the congruence relation on the ordinary locus. Further, we study the graph of supersingular Dieudonné crystals and liftings of isogenies to characteristic zero.

Soient 1 -> N -> H -> H' -> 1 une suite exacte centrale de groupes algébriques sur Q_p^alg et F un corps de nombres. Etant donnée une représentation Galoisienne r' : Gal_F -> H', on s'intéresse à ses relèvements à valeurs dans H à travers le morphisme H -> H'. Un relèvement r : Gal_F -> H sera dit minimal, s'il est non-ramifié aux places où r' est non-ramifiée et est de Rham/semi-stable/cristalline aux places divisant p si r' l'est. Dans cette thèse, nous montrons l'existence de relèvements minimaux dans certains cas. / Let 1 -> N -> H -> H' -> 1 be an exact sequence of algebraic groups over Q_p^alg and F be a number field. Given a Galois representation r' : Gal_F -> H', we are interested in its lifts with values in H through the morphism H -> H'. We say a lift r : Gal_F -> H is minimal, if it is unramied at places where r' is unramified and is de Rham/semi-stable/crystalline at p-adic places if r' is so. In this thesis, we prove the existence of such minimal lifts in some cases.

L'objet de cette thèse est la construction d'objets géométriques sur une variété C paramétrant des courbes rationnelles dans l'espace des twisteurs d'une variété hyperkählérienne. On établira une correspondance entre la géométrie complexe de l'espace des twisteurs et des propriétés différentielles sur C (opérateurs différentiels et courbure de la structure riemanienne complexe héritée de la variété hyperkählérienne). Les premiers chapitres précisent le cadre et les résultats connus. Dans les chapitres 4, 5 et 6 on établit une équivalence de catégories entre fibrés triviaux en restriction à chaque droite de l'espace des twisteurs et les fibrés à connexion sur C satisfaisant une condition de courbure. Le chapitre 7 prolonge cette correspondance sur le plan cohomologique tandis que le chapitre 8 en fait l'étude infinitésimale en reliant la courbure de la connexion avec les épaississements infinitésimaux des fibrés le long des droites. / The purpose of this thesis is to construct geometric objects on a manifold C parametrizing rational curves in the twistor space of a hyperkähler manifold. We shall establish a correspondence between the complex geometry of the twistor space and some differential properties of C (differential operators and curvature of a complex riemannian structure inherited from the base hyperkähler manifold). The first chapters gather some classical results of the theory of hyperkähler manifolds and their twistor spaces. In the chapters 4, 5 and 6, we construct an equivalence of categories between bundles on the twistor space which are trivial on each line and bundles with a connexion of C satisfying certain curvature conditions. The chapter 7 extends this correspondence on the cohomological level whereas the chapter 8 explores its infinitesimal version ; it links curvature of the connexion with thickening (in the sense of LeBrun) of the bundle along the lines.

<div>Let A be a d by n integer matrix. Gel'fand et al.\ proved that most A-hypergeometric systems have an interpretation as a Fourier–Laplace transform of a direct image. The set of parameters for which this happens was later identified by Schulze and Walther as the set of not strongly resonant parameters of A. A similar statement relating A-hypergeometric systems to exceptional direct images was proved by Reichelt. In the first part of this thesis, we consider a hybrid approach involving neighborhoods U of the torus of A and consider compositions of direct and exceptional direct images. Our main results characterize for which parameters the associated A-hypergeometric system is the inverse Fourier–Laplace transform of such a "mixed Gauss–Manin system". </div><div><br></div><div>If the semigroup ring of A is normal, we show that every A-hypergeometric system is "mixed Gauss–Manin". </div><div><br></div><div>In the second part of this thesis, we use our notion of mixed Gauss–Manin systems to show that the projection and restriction of a normal A-hypergeometric system to the coordinate subspace corresponding to a face are isomorphic up to cohomological shift; moreover, they are essentially hypergeometric. We also show that, if A is in addition homogeneous, the holonomic dual of an A-hypergeometric system is itself A-hypergeometric. This extends a result of Uli Walther, proving a conjecture of Nobuki Takayama in the normal homogeneous case.</div>

La première partie de la thèse traite des déformations et quantification de bialgèbres de Lie. L'existence d'une quantification pour chaque bialgèbre de Lie a été démontrée par Etingof et Kazhdan. Dans ce travail, on s'intéresse au cas des bialgèbres de Lie colorée, c'est à dire une structure de bialgèbres de Lie sur un espace gradué par un groupe quelconque et un bicaractère. A cet effet, on adapte la preuve de Etingof et Kazhdan et on introduit une généralisation au cas coloré du grand crochet introduit par Lecomte et Roger. Par ailleurs nous définissons une cohomologie pour les algèbres et bialgèbres de Lie colorées. Dans le deuxième partie de la thèse, on considère les algèbres Hom-associatives et algèbres Hom-Lie. Une algèbre Hom-associative est définie par une multiplication et une application linéaire alpha modifiant l'associativité. On commence cette partie par rappeler des définitions et propriétés des algèbres de type Hom. Ensuite, on définit la cohomologie de Hochschild de type alpha, en donnant ses propriétés. Une étude similaire est faite dans le cas des algèbres Hom-Lie et la cohomologie de Chevalley-Eilenberg, ainsi que pour les Hom-bialgèbres et bialgèbres Hom-Lie. La théorie de déformations formelles introduite par Gerstenhaber met en lien les déformations et la cohomologie. Dans cette thèse on établit une théorie de déformations des algèbres Hom-associatives basée sur la cohomologie de Hochschild de type alpha. Il s'agit de déformer simultanément la multiplication et l'application linéaire. Par ailleurs, on explore la structure d’algèbre de Lie à homotopie près correspondante, telle que les éléments de Maurer-Cartan sont des Hom-algèbres. / In the first part of this thesis, we provide a proof that any color Lie bialgebra can be quantized. This was proved for Lie bialgebras by Etingof and Kazhdan. Here we generalize this proof to color Lie bialgebras, which are Lie bialgebras graded by an arbitrary abelian group and symmetry given by a bicharacter. Before giving the details of the proof, we first recall the definitions and basic properties of color Lie algebras and bialgebras. Also a generalization of the Grand Crochet introduced by Lecomte and Roger to the color setting is given. Using the Grand Crochet, we also provide a cohomology for color Lie bialgebras. In the second part, we study different type of Hom-algebras, especially Hom-Lie and Hom-associative algebras. Hom-algebras are algebras were the defining relations, e.g. the associativity, are twisted by a linear map alpha called structure map. We first recall the relevant definitions. Then we define a new cohomology for Hom-associative and Hom-Lie algebras called alpha-type Hochschild and Chevalley-Eilenberg cohomology respectively. We also show how these cohomologies can be used to study formal deformations, in the sense of Gerstenhaber, of Hom-associative and Hom-Lie algebras. We allow the deformation of the multiplication and the structure map. We also consider alpha type cohomologies for Hom-bialgebras. Moreover, we explore the corresponding homotopy Lie algebra structure such that the Maurer-Cartan elements are Hom-algebras.

[pt] Esta dissertação tem como objetivo exibir uma fórmula para cálcular o anel de cohomologia de um fibrado flag homogêneo de um grupo de Lie G compacto e conexo. Para concluir o resultado é usado a cohomologia equivariante, em particular, sua abordagem mais algébrica. Isto implica introduzir G- módulos e sua teoria equivariante, o que passa também por introduzir a álgebra de Weil, o modelo de Cartan e o homomorfismo característico. A demonstração do resultado também está fortemente baseada nas propriedades algébricas dos toros maximais de G. / [en] The purpose of this dissertation is to present a formula for calculating the cohomology ring of a homogeneous flag bundles of a compact and connected Lie G group. To conclude the result, the equivalent cohomology is used, in particular, its more algebraic approach. This implies introducing G modules and their equivalent theory, which also involves introducing Weil algebra, Cartans model and characteristic homomorphism. The income statement is also strongly based on the algebraic properties of the maximal torus of G.

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<p>Arising from permutation representations of finite groups, Brauer-Kuroda relations are relations between Dedekind zeta functions of certain intermediate fields of a Galois extension of number fields. Let E be a totally real number field and let n ≥ 2 be an even integer. Taking s = 1 − n in the Brauer-Kuroda relations then gives a correspondence between orders of certain motivic and Galois cohomology groups. Following the works of Voevodsky and Wiles (cf. [33], [36]), we show that these relations give a direct relation on the motivic cohomology groups, allowing one to easily compute the higher class numbers, the orders of these motivic cohomology groups, of fields of high degree over Q from the corresponding values of its subfields. This simplifies the process by restricting the computations to those of fields of much smaller degree, which we are able to compute through Sage ([30]). We illustrate this with several extensive examples.</p> / Master of Science (MSc)