El presente trabajo tiene por objetivo presentar una versión del Teorema del Flujo Tubular que sirva de motivación para introducir objetos geométricos como fibrado tangente, subfibrado tangente, X-foliación, entre otros. Esta presentación resulta ser el caso 1-dimensional del Teorema de Frobenius, lo que nos permitirá ver con claridad qué tipo de problema es el que resuelve dicho teorema, facilitando la comprensión del caso k-dimensional de tan importante teorema. / --- The objetive of this work is to present a version of the Tubular Flow Theorem that motivates the introduction of geometric objects such as: tan- gent bundle, tangent subbundle, X-foliation, etc. This presentation becomes the 1-dimensional case of the Frobenius Theorem, which will let us see what kind of problem this theorem solves, in order to improve the comprehension of the k-dimensional case of such as important theorem. / Tesis

There is a well-known correspondence between two-dimensional topological quantum field theories (2-D TQFTs) and commutative Frobenius algebras. Every 2-D TQFT also gives rise to a diffeomorphism invariant of closed, orientable two-manifolds, which may be investigated via the associated commutative Frobenius algebras. We investigate which such diffeomorphism invariants may arise from TQFTs, and in the process uncover a distinction between two fundamentally different types of commutative Frobenius algebras ("weak" Frobenius algebras and "strong" Frobenius algebras). These diffeomorphism invariants form the starting point for our investigation into marked cobordism categories, which generalize the local cobordism relations developed by Dror Bar-Natan during his investigation of Khovanov's link homology. We subsequently examine the particular class of 2-D TQFTs known as "universal sl(n) TQFTs". These TQFTs are at the algebraic core of the link invariants known as sl(n) link homology theories, as they provide the algebraic structure underlying the boundary maps in those homology theories. We also examine the 3-manifold diffeomorphism invariants known as skein modules, which were first introduced by Marta Asaeda and Charles Frohman. These 3-manifold invariants adapt Bar-Natan's marked cobordism category (as induced by a specific 2-D TQFT) to embedded surfaces, and measure which such surfaces may be embedded within in 3-manifold (modulo Bar-Natan's local cobordism relations). Our final results help to characterize the structure of such skein modules induced by universal sl(n) TQFTs.

Landau-Ginzburg Mirror Symmetry provides for the construction of two algebraic objects, called the A- and B-models. Special cases of these models–constructed using invertible polynomials and abelian symmetry groups–are well understood. In this thesis, we consider generalizations of the B-model, and specifically address the associativity of the multiplication in these models. We also prove an explicit B-model isomorphism for a class of polynomials in three variables.

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Dans cette thèse, on considère des revêtements séparables à deux ouverts de la droite projective sur un corps fini k de caractéristique p>0 et on donne un calcul explicite de la matrice du Frobenius divisé sur le premier espace de cohomologie de Rham de X_k, fibre spéciale du revêtement X étudié. On fournit également un procédé algorithmique permettant d'obtenir la décomposition de Jordan-Hölder du φ-module filtré associé à cette matrice. / We consider X some separable covering with two open set of the projective line on a finite field k of caracteristic p>0 and we give an explicit computation of the matrix of the divided Frobenius on the first de Rham cohomology space of X_k the special fiber of X. We also explain an algorithmic process to get the Jordan-Hölder decomposition of the φ-module associated to this matrix.

Dans cette thèse, nous décrivons une réalisation géométrique des carquois de type Dynkin, et certains carquois euclidiens. Nous traitons le cas D ̃n en profondeur et démontrons quelques résultats complémentaires aux travaux de Baur, Marsh et Torkildsen sur les réalisations géométriques des catégories amassées supérieures. Pour le cas D ̃n, on trouve la figure qui correspond à l'étude, on démontre la compatibilité entre le flip d'une (m+2)-angulation, et la mutation de carquois coloré. On trouve une bijection entre les objets m-rigides et chaque arc dit admissible, puis entre les objets amas-basculants et les (m+2)-angulations. De plus, on démontrela compatibilité entre la réduction d'Iyama-Yoshino, et le fait de couper le long d'un arc, qu'on définira formellement. Nous démontrons aussi qu'une catégorie exacte est une catégorie de préfibration au sens de Anderson-Brown-Cisinski, qui vérifie le théorème de Quillen, et une catégorie de Frobenius est munie d'une structure de modèle, compatible avec le passage à la catégorie stable, qui est triangulée / We show that a subcategory of the m-cluster category of type D ̃n is isomorphic to a category consisting of arcs in an (n - 2)m-gon with two central (m - 1)-gons inside of it. We show that the mutation of colored quivers and m-cluster-tilting objects is compatible with the flip of an (m + 2)-angulation. In this thesis, we study the geometric realizations of m-cluster categories of Dynkin types A, D, A ̃ and D ̃. We show, in those four cases, that there is a bijection between (m + 2)-angulations and isoclasses of basic m-cluster tilting objects. Underthese bijections, flips of (m + 2)-angulations correspond to mutations of m-cluster tilting objects. Our strategy consists in showing that certain Iyama-Yoshino reductions of the m-cluster categories under consideration can be described in terms of cutting along an arc the corresponding geometric realizations. This allows to infer results from small cases to the general ones. Let Ɛ be a weakly idempotent complete exact category with enough injective and projective objects. Assume that M ⊆ Ɛ is a rigid, contravariantly finite subcategoryof Ɛ containing all the injective and projective objects, and stable under taking direct sums and summands. In this paper, Ɛ is equipped with the structure of a prefibration category with cofibrant replacements. As a corollary, we show, using the results of Demonet and Liu in [DL13], that the category of finite presentation modules on the costable category M is a localization of Ɛ. We also deduce that Ɛ → modM admits a calculus of fractions up to homotopy. These two corollaries are analogues for exact categories of results of Buan and Marsh in [BM13], [BM12] (see also [Bel13]) that hold for triangulated categories. If Ɛ is a Frobenius exact category, we enhance its structure of prefibration category to the structure of a model category (see the article of Palu in [?] for the case of triangulated categories). This last result applies in particular when Ɛ is any of the Hom-finite Frobenius categories appearing in relation to cluster algebras

This thesis examines the Mordell-Weil group for application in cryptography. This approach has recently been proposed by Gerhard Frey. The use of the Mordell-Weil group for discrete logarithm schemes is a variant of elliptic curve cryptosystems. We extended the original idea by Frey with the goal of a performance improvement. The arithmetic complexity using the Mordell-Weil group will be compared to ordinary elliptic curve cryptosystems. The main goals of this thesis are (1) to investigate the algorithmic complexity of Mordell-Weil cryptosystems relative to elliptic curve cryptosystems; (2) the appropriate selection of the group parameters for a successful adaptation to different platforms; (3) a C++ library which makes it possible to easily use this algebra for cryptographic systems based on groups; and (4) to obtain software performance measures for the new cryptosystem. Point multiplication, the crucial operation for elliptic curve cryptosystems, is more than 20% less complex in the Mordell-Weil group than in an ordinary elliptic curve while preserving the same level of security. We show how to further improve the system such that it is particularly suited to 32-bit and 16-bit hardware platforms. The speed-up of the Mordell-Weil group approach comes at the cost of a slightly larger bit-size that is needed to represent a curve point and a more costly curve generation.

Les variétés de Frobenius ont été introduites par B. Dubrovin dans les années 1990. Ces variétés sont en bijection avec les solutions du système d'équations différentielles de Witten-Dijkgraaf-Verlinde-Verlinde (WDVV) qui est apparu dans l'étude des déformations des théories de champs conformes en deux dimensions. Les structures d'une variété de Frobenius ont été trouvées dans plusieurs contextes, en particulier, sur les espaces de Hurwitz (les espaces de fonctions méromorphes sur des surfaces de Riemann). Ces dernières structures, appelées les variétés de Hurwitz-Frobenius, présentent des exemples très intéressants de variétés de Frobenius. L'aspect le plus intéressant c'est que nous pouvons étudier tous les objets liés à la variété de la façon explicite en utilisant la théorie des fonctions sur les surfaces de Riemann. Le but de ce mémoire est de calculer explicitement les solutions du système WDVV, appelées prépotentiels, qui correspondent à trois variétés de Hurwitz-Frobenius particulières.

A proposta principal desta. dissertação é provar a existência de medidas invariante absolutamente contínuas para uma clas$e de funções monótonas por partes com um número finito de descontinuidade mas o resultado pode ser estedido para funções monótonas por partes com um número infini to de descontinuidades. O método de prova explora a existência de pontos fixos para o operador de Perron- Frobenius e utiliza o Teorema de Helly e o Teorema Ergódico de Kakutani-Yosida. / The main purpose of this dissertation is to prove the existence of invariant absolutely continuous measures for a class of piecewise monotonic functions with a finite number of descontinuities but it can be extended to piecewise monotonic functions with infinite numbers of descontinuities. The method of the proof explores the existence of fixe·d points to Perron-Frobenius operator and employs the Helly's Theorem and the Kakutani - Yosida ergodic Theorem.

A proposta principal desta. dissertação é provar a existência de medidas invariante absolutamente contínuas para uma clas$e de funções monótonas por partes com um número finito de descontinuidade mas o resultado pode ser estedido para funções monótonas por partes com um número infini to de descontinuidades. O método de prova explora a existência de pontos fixos para o operador de Perron- Frobenius e utiliza o Teorema de Helly e o Teorema Ergódico de Kakutani-Yosida. / The main purpose of this dissertation is to prove the existence of invariant absolutely continuous measures for a class of piecewise monotonic functions with a finite number of descontinuities but it can be extended to piecewise monotonic functions with infinite numbers of descontinuities. The method of the proof explores the existence of fixe·d points to Perron-Frobenius operator and employs the Helly's Theorem and the Kakutani - Yosida ergodic Theorem.