Search

We first develop a general theory of Johnson filtrations and Johnson homomorphisms for a group $G$ acting on another group $K$ equipped with a filtration indexed by a "good" ordered commutative monoid. Then, specializing it to the case where the monoid is the additive monoid $\mathbb{N}^2$ of pairs on nonnegative integers, we obtain a theory of double Johnson filtrations and homomorphisms. We apply this theory to the mapping class group $\mathcal{M}$ of a surface $\Sigma_{g,1}$ with one boundary component, equipped with the normal subgroups $\bar{X}$, $\bar{Y}$ of $\pi_1(\Sigma_{g,1})$ associated to a standard Heegaard splitting of the $3$-sphere. We also consider the case where the group $G$ is the automorphism group of a free group., Comment: 42 pages, some figures. Remark 4.17 and reference [8] added

Let Σ be a compact oriented surface with one boundary component and let M denote the mapping class group of Σ. By considering the action of M on the fundamental group of Σ it is possible to define different filtrations of M together with some homomorphisms on each term of the filtrations. The aim of this thesis is twofold. First, we study two filtrations of M : the « Johnson-Levine filtration » introduced by Levine and « the alternative Johsnon filtration » introduced recently by Habiro and Massuyeau. The definition of both filtrations involve a handlebody bounded by Σ. We refer to these filtrations as ≪ Johnson-type filtrations » and the corresponding homomorphisms have referred to as « Johnson-type homomorphisms » by their analogy with the original Johnson filtration and the usual Johnson homomorphisms. We provide a comparison of the Johnson filtration with the Johnson-Levine filtration at the level of the monoid of homology cobordisms of Σ. We also provide a comparison of the alternative Johnson filtration with the Johnson-Levine filtration and the Johnson filtration at the level of the mapping class group. Secondly, we study the relationship between the « Johnson-type homomorphisms » and the functorial extension of the universal perturbative invariant of 3-manifolds (the Le-Murakami-Ohtsuki invariant or LMO invariant). This functorial extension is calling the LMO functor and it takes values in a category of diagrams. We prove that the « Johnson-type homomorphisms » is in the tree reduction of the LMO functor. In particular, this provides a new reading grid of the tree reduction of the LMO functor., Soit Σ une surface compacte connexe orientée avec une seule composante du bord. Notons par M le groupe d'homéotopie de Σ. En considérant l'action de M sur le groupe fondamental de Σ, il est possible de définir différentes filtrations de M ainsi que des homomorphismes sur chaque terme de ces filtrations. Le but de cette thèse est double. En premier lieu, nous étudions deux filtrations de M : la " filtration de Johnson-Levine " introduite par Levine et la " filtration de Johnson alternative " introduite recemment par Habiro et Massuyeau. Les définitions de ces deux filtrations prennent en compte un corps en anses bordé par la surface. Nous nous référons à ces filtrations comme " filtrations de type Johnson " et les homomorphismes correspondants sont appelés " homomorphismes de type Johnson " par leur analogie avec la filtration de Johnson originale et les homomorphismes de Johnson usuels. Nous donnons une comparaison de la filtration de Johnson avec la filtration de Johnson-Levine au niveau du monoïde des cobordismes d'homologie de Σ. Nous donnons également une comparaison entre la filtration de Johnson alternative, la filtration Johnson-Levine et la filtration de Johnson au niveau du groupe d'homéotopie. Deuxièmement, nous étudions la relation entre les " homomorphismes de type Johnson" et l'extension fonctorielle de l'invariant perturbatif universel des variétés de dimension trois (l'invariant de Le-Murakami-Ohtsuki ou invariant LMO). Cette extension fonctorielle s'appelle le foncteur LMO et il prend ses valeurs dans une catégorie de diagrammes. Nous démontrons que les "homomorphismes de type Johnson " peuvent être lus dans la réduction arborée du foncteur LMO. En particulier, cela fournit une nouvelle grille de lecture de la réduction arborée du foncteur LMO.

"La construcción de viviendas con muros delgados de concreto reforzado y cuantías de refuerzo mínimas ha venido aumentando paulatinamente hasta convertirse en una práctica común en varias zonas de país. Viviendas entre uno, dos y tres pisos de altura, se construyen con muros que no superan los 10 centímetros de espesor reforzados con una malla electro soldada ubicada en la sección media del muro... Esta investigación busca definir bajo qué condiciones serían una opción viable para la construcción de viviendas de baja altura en Colombia. Los resultados obtenidos permiten concluir que una disminución hasta del 50% en el refuerzo a cortante o el uso de fibras como remplazo del refuerzo a corte en muros de viviendas de baja altura, podrían aplicarse sin comprometer la seguridad del sistema estructural en zonas de amenaza sísmica baja o intermedia según la norma colombiana" -- Tomado del Formato de Documento de Grado. "Construction of housing with reinforced concrete thin walls and minimum reinforcement has gradually become a common practice in several areas of the country. Structures between one and three stories are built using thin walls with welded-wire meshes as web reinforcement... This research has the purpose of evaluating the effects of reducing shear reinforcement or replacing conventional concrete walls with fiber reinforced concrete walls on the seismic behavior of low-rise housing constructions. The results show that a reduction of fifty percent in shear reinforcement is possible in low or intermediate seismic hazard areas without affecting the structural safety of the system." -- Tomado del Formato de Documento de Grado. Magíster en Ingeniería Civil Maestría

Let $\Sigma$ be a compact connected oriented surface with one boundary component and let $\mathcal{M}$ denote the mapping class group of $\Sigma$. By considering the action of $\mathcal{M}$ on the fundamental group of $\Sigma$ it is possible to define different filtrations of $\mathcal{M}$ together with some homomorphisms on each term of the filtration. The aim of this paper is twofold. Firstly we study a filtration of $\mathcal{M}$ introduced recently by Habiro and Massuyeau, whose definition involves a handlebody bounded by $\Sigma$. We shall call it the "alternative Johnson filtration", and the corresponding homomorphisms are referred to as "alternative Johnson homomorphisms". We provide a comparison between the alternative Johnson filtration and two previously known filtrations: the original Johnson filtration and the Johnson-Levine filtration. Secondly, we study the relationship between the alternative Johnson homomorphisms and the functorial extension of the Le-Murakami-Ohtsuki invariant of $3$-manifolds. We prove that these homomorphisms can be read in the tree reduction of the LMO functor. In particular, this provides a new reading grid for the tree reduction of the LMO functor., Comment: 62 pages, several figures. v_2 minor changes