Orientador: Alice Kimie Miwa Libardi / Banca: Pedro Luiz Queiroz Pergher / Banca: Denise de Mattos / Resumo: O objetivo principal deste trabalho é apresentar um estudo sobre Homologia de Espaços Fibrados, baseado no livro Elements of Homotopy Theory de G.W.Whitehead. O conceito de fibração apareceu em torno de 1930 e pode ser visto como uma extensão da teoria de fibrados. Existe uma sequência exata longa que relaciona os grupos de homotopia dos espaços base, total e da fibra de uma fibração. Porém, relacionar os grupos de homologia desses espaços é uma tarefa mais complicada. O caso geral é feito utilizando sequências espectrais. Porém, há casos particulares em que podemos obter relações sem utilizar a maquinaria das sequências espectrais / Abstract: The main goal of this work is to present a study on Homology of Fibre Spaces, based on the book of G.W. Whitehead: "Elements of Homotopy Theory". The concept of fibration appeared around 1930 and can be seen as an extension of the theory of bundles. There is a long exact sequence that relates the homotopy groups of the total, base and fiber spaces of a fibration. However, relating the homology groups of such spaces is more complicated. The general case is obtained using spectral sequences. Nevertheless there are particular cases where one can obtain such relations without the need of the machinery of spectral sequences / Mestre

Le but principal de la topologie algébrique dirigée est d’étudier des systèmes qui évoluent avec le temps à travers leur géométrie. Ce sujet émergea en informatique, plus particulièrement en vraie concurrence, où Pratt introduisit les automates de dimension supérieure (HDA) en 1991 (en réalité, l’idée de la géométrie de la concurrence peut être retracée jusque Dijkstra en 1965). Ces automates sont géométriques par nature: chaque ensemble de n processus exécutant des actions indépendantes en parallèle peuvent être modélisées par un cube de dimension n, et un tel automate donne naissance à un espace topologique, obtenu en recollant ces cubes. Cet espace a naturellement une direction du temps provenant du flot d’exécution. Il semble alors totalement naturel d’utiliser des outils provenant de la topologie algébrique pour étudier ces espaces: les chemins modélisent les exécutions et les homotopies de chemins, c’est-à-dire les déformations continues de chemins, modélisent l’équivalence entre exécutions modulo ordonnancement d’actions indépendantes, mais ces notions géométriques doivent préserver la direction du temps, d’une façon ou d’une autre. Ce caractère dirigé apporte des complications et la théorie doit être refaite, essentiellement depuis le début. Dans cette thèse, j’ai développé des théories de l’homotopie et de l’homologie pour ces espaces dirigés. Premièrement, ma théorie de l’homotopie dirigée est basée sur la notion de rétracts par déformations, c’est-à-dire de déformations continues d’un gros espaces sur un espace plus petit, suivant des chemins inessentiels, c’est-à-dire qui ne changent pas le type d’homotopie des « espaces d’exécutions ». Cette théorie est reliée aux catégories de composantes et catégories de dimension supérieures. Deuxièmement, ma théorie de l’homologie dirigée suit l’idée que l’on doit regarder les « espaces d’exécutions » et comment ceux-ci évoluent avec le temps. Cette évolution temporelle est traitée en définissant cette homologie comme un diagramme des « espaces d’exécutions » et en comparant de tels diagrammes en utilisant une notion de bisimulation. Cette théorie homologique a de très bonnes propriétés: elle est calculable sur des espaces simples, elle est un invariant de notre théorie homotopique, elle est invariante par des raffinements d’actions simples et elle une théorie des suites exactes. / Studying a system that evolves with time through its geometry is the main purpose of directed algebraic topology. This topic emerged in computer science, more particularly in true concurrency, where Pratt introduced the higher dimensional automata (HDA) in 1991 (actually, the idea of geometry of concurrency can be tracked down Dijkstra in 1965). Those automata are geometric by nature: every set of n processes executing independent actions can be modeled by a n-cube, and such an automaton then gives rise to a topological space, obtained by glueing such cubes together. This space naturally has a specific direction of time coming from the execution flow. It then seems natural to use tools from algebraic topology to study those spaces: paths model executions, homotopies of paths, that is continuous deformations of paths, model equivalence of executions modulo scheduling of independent actions, and so on, but all those notions must preserve the direction. This brings many complications and the theory must be done again.In this thesis, we develop homotopy and homology theories for those spaces with a direction. First, my directed homotopy theory is based on deformation retracts, that is continuous deformation of a big space on a smaller space, following directed paths that are inessential, meaning that they do not change the homotopy type of spaces of executions. This theory is related to categories of components and higher categories. Secondly, my directed homology theory follows the idea that we must look at the spaces of executions and those evolves with time. This evolution of time is handled by defining such homology as a diagram of spaces of executions and comparing such diagrams using a notion of bisimulation. This homology theory has many nice properties: it is computable on simple spaces, it is an invariant of our homotopy theory, it is invariant under simple action refinements and it has a theory of exactness.

This thesis is about how to interpret metric data with topological tools, such as homology. We show how to go from a metric space to a topological space via Vietoris-Rips complexes. We use the usual approach to Topological Data Analysis (TDA), and transform our metric space into tame parametrised vector spaces. It is then shown how to simplify tame parametrised vector spaces. We also present another approach to TDA, where we transform our metric space into a filtrated tame parametrised chain complex. We then show how to simplify chain complexes over fields in order to simplify tame parametrised filtrated chain complexes. / Denna uppsats handlar om att tolka metrisk data med hjälp utav topologiska verktyg, som exempelvis homologi. Vi visar hur man går från ett metriskt rum till ett topologiskt rum via Vieteris-Rips komplex. Vi använder den vanliga metoden till Topologisk Data Analys (TDA), och transformerar vårat metriska rum till tama parametriserade vektorrum. Det visas sedan hur vi kan förenkla tama parametriserade vektorrum. Vi presenterar även en annan metod för TDA, där vi går från ett metriskt rum till ett filtrerat tamt parametriserat kedjekomplex. Sedan visar vi hur man förenklar kedjekomplex över kroppar för att kunna förenkla filtrerade tama parametriserade kedjekomplex.

A configuration space is a space whose points represent the possible states of a given physical system. As such they appear naturally both in theoretical physics and technical applications. For an example of the former, in analytical mechanics, the Lagrangian and Hamiltonian formulations of classical mechanics depend heavily on the use of a physical system’s configuration space for the description of its kinematical and dynamical behavior, and importantly, its evolution in time. As an example of a technical application, consider robotics, where the space of possible configurations of the mechanical linkages that make up a robot is an important tool in motion planning. In this case it is of particular interest to study the singularities of these mechanical linkages, to see if a given configuration is singular or not. This can be done with the help of configuration spaces and their topological properties. Arguably, the simplest configuration space possible arises when the system is just a collection of point-like particles in a plane. Despite its simplicity, the corresponding configuration space has substantial complexity and is of great interest in mathematics, physics and technology: For instance, it arises naturally in the mathematical modelling of robots performing tasks in a warehouse. In this thesis we go through the mathematics necessary to study the behaviour of paths in this space, which corresponds to motions of the particles. We use the theory of groups, algebraic topology, and manifolds to examine the properties of the configuration space of point-like particles in a plane. An important role in the discussion will be played by braids, which are certain collections of curves, interlaced in three-space. They are connected to many different topics in algebra, geometry, and mathematical physics, such as representation theory, the Yang-Baxter equation and knot theory. They are also important in their own right. Here we focus on their relation to configurations of points.

We present a rigorous yet accessible introduction to structures on finite sets foundational for a formal study of complex networks. This includes a thorough treatment of binary relations, distance spaces, their properties and similarities. Correspondences between relations and graphs are given and a brief introduction to graph theory is followed by a more detailed study of cohesiveness and centrality. We show how graph degeneracy is equivalent to the concept of k-cores, which give a measure of the cohesiveness or interconnectedness of a subgraph. We then further extend this to d-cores of directed graphs. After a brief introduction to topology, focusing on topological spaces from distances, we present a historical discussion on the early developments of algebraic topology. This is followed by a more formal introduction to simplicial homology where we define the homology groups. In the context of algebraic topology, the d-cores of a digraph give rise to a partially ordered set of subgraphs, leading to a set of filtrations that is two-dimensional in nature. Directed clique complexes of digraphs are defined in order to encode the directionality of complete subdigraphs. Finally, we apply these methods to the neuronal network of C.elegans. Persistent homology with respect to directed core filtrations as well as robustness of homology to targeted edge percolations in different directed cores is analyzed. Much importance is placed on intuition and on unifying methods of such dispersed disciplines as sociology and network neuroscience, by rooting them in pure mathematics. / Vi presenterar en rigorös men lättillgänglig introduktion till de abstrakta strukturer på ändliga mängder som är grundläggande för en formell studie av komplexa nätverk. Detta inkluderar en grundlig redogörelse av binära relationer och distansrum, deras egenskaper samt likheter. Korrespondenser mellan olika typer av relationer och grafer förklaras och en kort introduktion till grafteori följs av en mer detaljerad studie av sammanhållning och centralitet. Vi visar hur begreppet 'degeneracy' är ekvivalent med begreppet k-kärnor (eng: k-cores), vilket ger ett mått på sammanhållningen hos en delgraf. Vi utökar sedan detta till konceptet d-kärnor (eng: d-cores) för riktade grafer. Efter en kort introduktion till topologi med fokus på topologiska rum från distansrum, så presenterar vi en historisk diskussion kring den tidiga utvecklingen av algebraisk topologi. Detta följs av en mer formell introduktion till homologi, där vi bl.a. definierar homologigrupperna. Vi definierar sedan så kallade riktade klick-komplex som simplistiska komplex (eng: simplicial complexes) från riktade grafer, där d-kärnorna av en riktad graf då ger upphov till filtrerade komplex i två parametrar. Persistent homologi med avseende på dessa riktade kärnfiltreringar såväl som robusthet mot kantpercolationer i olika kärnor analyseras sedan för det neurala nätverket hos C.Elegans. Stor vikt läggs vid intuition och förståelse, samt vid att förena metodiker för så spridda discipliner som sociologi och neurovetenskap.

We define and study the fundamental pro-finite 2-groupoid of varieties X defined over a field k. This is a higher algebraic invariant of a scheme X, analogous to the higher fundamental path 2-groupoids as defined for topological spaces. This invariant is related to previously defined invariants, for example the absolute Galois group of a field, and Grothendieck’s étale fundamental group. The special case of Brauer-Severi varieties is considered, in which case a “sections conjecture” type theorem is proved. It is shown that a Brauer-Severi variety X has a rational point if and only if its étale fundamental 2-groupoid has a special sort of section.

We interpret the generalised gauge symmetry introduced in string theory and M-Theory as a special case of Grothendieck's stability equivalence relation in the definition of the 0th K-group and we calculate the Euler number of the elliptic de Rham complex twisted by a flat connection. Then using Polyakov's classical equivalence of flat bundles with non-linear sigma models we define a new topological invariant for foliations using techniques from noncommutative geometry, in particular the Connes' pairing between K-Theory and cyclic cohomology. This new invariant classifies foliations up to Morita equivalence.

Symplectic geometry can be traced back to Lagrange and his work on celestial mechanics and has since then been a very active field in mathematics, partly because of the applications it offers but also because of the beauty of the objects it deals with. I this thesis we begin by the simplest fact of symplectic geometry. We give the definition of a symplectic space and of the symplectic group, Sp(n). A symplectic space is the data of an even-dimensional space and of a form which satisfies a number of properties. Having done this we give a definition of the Lagrangian Grassmannian Lag(n) which consists of all n-dimensional subspaces of the symplectic space on which the symplectic form vanishes. We carefully study the topology of these spaces and their universal coverings. It is of great interest to know how the elements of the Lagrangian Grassmannian intersect each other. A lot of efforts have therefore been made to construct intersection indices for elements of Lag(n). They have gone under many names but have had a sole purpose, namely to give us a way to determine how these elements intersect. We show how these elements are constructed and extend the definition to paths of elements of Lag(n) and Sp(n). We end this thesis by extending the definition of an index defined by Conley and Zehnder bu using the properties of the Leray index. Their index plays a significant role in the theory of periodic Hamiltonian orbit.

A state sum is an expression approximating the partition function of a d-dimensional field theory on a closed d-manifold from a triangulation of that manifold. To consider state sums in completely local 2-dimensional topological field theories (TFT's), we introduce a mechanism for incorporating triangulations of surfaces into the cobordism ([infinity],2)-category. This serves to produce a state sum formula for any fully extended 2-dimensional TFT possibly with extra structure. We then follow the Cobordism Hypothesis in classifying fully extended 2-dimensional G-equivariant TFT's for a finite group G. These are oriented theories in which bordisms are equipped with principal G-bundles. Combining the mechanism mentioned above with our classification results, we derive Turaev's state sum formula for such theories. / text

L'objectif de ce travail est l'étude de la K-théorie réelle connexe des 2-groupes abéliens élémentaires, c'est-à-dire, pour V un 2-groupe abélien élémentaire, l'objet kR^{\star}(BV ). Cet objet contient, entre autres, la K-théorie orthogonale connexe ko et la K-théorie unitaire connexe ku des 2-groupes abéliens élémentaires, et est naturellement muni d'une structure de Z[v1]-module, où v1 désigne la classe de Bott réelle, un relèvement équivariant en K-théorie réelle de la classe de Bott en K-théorie unitaire. En utilisant des outils provenant de la théorie d'homotopie stable Z/2-équivariante, et en particulier la tour des tranches, une tour naturelle dans la catégorie stable équivariante introduite dans les travaux récents de Hill, Hopkins et Ravenel, on montre que les éléments de torsion pour la classe de Bott réelle dans la K-théorie réelle des 2-groupes abéliens élémentaires sont annulés par la multiplication par v2 1. On effectue une étude détaillée de l'algèbre de Steenrod Z/2-équivariante A, constituée des opérations en HF2-cohomologie, et de sa relation avec l'algèbre de Steenrod classique modulo 2. On exhibe en particulier, pour tout entier n, des sous-algèbres extérieures de l'algèbre de Steenrod équivariante E(\beta_0,...,\beta_n), générées par certaines opérations \beta_ i, i entier, qui est une version Z/2-équivariante de la sous algèbre de l'algèbre de Steenrod modulo 2 engendrée par les n+1 premières opérations de Milnor. On s'intéresse ensuite l'algèbre homologique relative, dans la catégorie des E(\beta_0,\beta_1)-modules, relativement au sous-anneau E(\beta_0), et on introduit des outils de calcul très généraux permettant en particulier de déterminer tous les groupes d'extension relatifs Ext(F2,HF2^{\star}(BV )). On introduit ensuite la propriété de h-détection pour une tour d'objets dans une catégorie triangulée, et on relie les propriétés de h-détection à l'estimation de la v1-torsion de la K-théorie réelle connexe. On étudie ensuite l'obstruction pour qu'une tour vérifie la propriété de h-détection, pour h = 1 ou 2. On montre ensuite que l'obstruction pour que la tour des tranches de la K-théorie réelle vérifie la propriété de 2-détection est contrôlée par Ext(F2,HF2^{\star}(BV )), qu'on a calculé précédemment. Le résultat précédent concernant la v1-torsion de la K-théorie réelle des 2-groupes abéliens élémentaires suit. Une des applications de ce résultat est une détermination explicite de kR^{\star}(BV ).