Doctor of Philosophy / Department of Mathematics / Gerald H. Hoehn / In this work, we study the complex N-Spin bordism groups of semifree circle actions and elliptic genera of level N. The notion of complex N-Spin manifolds (or simply N-manifolds) was introduced by Hoehn in [Hoh91]. Let the bordism ring of such manifolds be denoted by U;N and the ideal in U;N Q generated by bordism classes of connected complex N-Spin manifolds admitting an e ffective circle action of type t be denoted by IN;t. Also, let the elliptic genus of level n be denoted by 'n. It is conjectured in [Hoh91] that IN;t = \ njN n - tker('n): Our work gives a complete bordism analysis of rational bordism groups of semifree circle actions on complex N-Spin manifolds via traditional geometric techniques. We use this analysis to give a determination of the ideal IN;t for several N and t, and thereby verify the above conjectural equation for those values of N and t. More precisely, we verify that the conjecture holds true for all values of t with N 9, except for case (N; t) = (6; 3) which remains undecided. Moreover, the machinery developed in this work furnishes a mechanism with which to explore the ideal INt for any given values of N and t.

Our aim is to study the role of omnioriented quasitoric manifolds in equivariant complex bordism. These are a well-behaved class of even-dimensional smooth closed manifolds with the action of a half-dimensional compact torus and an equivariant stably complex structure. They are beneficial objects to work with as they can be described completely in terms of combinatorial data.We include an overview of equivariant complex bordism, highlighting the relationship between localisation and restriction to fixed point data. By keeping in mind the particularly interesting case when the group in question is the compact torus, we revisit work found in [BPR10], reinterpreting and expanding certain results relating to the universal toric genus.We then consider oriented torus graphs of stably complex torus manifolds and classify these using a boundary operator on exterior polynomials related to geometric equivariant complex bordism classes of the manifolds. We also extend the connected sum construction of quasitoric pairs which allows for a more general notion of the equivariant connected sum of omnioriented quasitoric manifolds.We then consider whether an equivariant version of Buchstaber and Ray’s result in [BR98] holds; that is, does there exist an omnioriented quasitoric manifold in every geometric equivariant complex bordism class in which they naturally exist? We conjecture that this is true showing that we have a combinatorial model for such objects and exhibiting low-dimensional examples.

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

Neste trabalho, estudamos coincidências entre duas aplicações contínuas f e g, de X em Y, onde X e Y são variedades diferenciáveis, conexas, sendo X fechada (n+1)-dimensional e Y sem bordo n-dimensional. Quando o domínio é a esfera e g é constante, consideramos homomorfismos w\' e w\'\' que juntos determinam o invariante de bordismo normal do par (f,g). Calculamos w\'\' para vários espaços e, em particular, para fibrados esféricos sobre esferas, obtemos que w\'\' é identicamente nulo se, e somente se, Y é trivial ou Y não é um S&#178-fibrado sobre S&#8308. Finalmente, obtemos resultados tipo Wecken quando X é a esfera, e quando X é o espaço projetivo real de dimensão 3 e Y é a esfera de dimensão 2. / In this work, we study coincidences between two maps f and g, from X to Y, where X and Y are smooth manifolds, connected, being X closed (n+1)-dimensional and Y without boundary n-dimensional. When the domain is the sphere and g is constant, we consider homomorphisms w\' and w\'\' which together determine the normal bordism invariant of the pair (f,g). We calculate w\'\' for several spaces and, in particular, for sphere bundles over spheres, we obtain that w\'\' is identically null if and only if Y is trivial or Y is not an S&#178-bundle over S&#8308. Finally, we obtain Wecken type results when X is the sphere, and when X is the 3-dimensional real projective space and Y is the 2-dimensional sphere.

Neste trabalho, estudamos coincidências entre duas aplicações contínuas f e g, de X em Y, onde X e Y são variedades diferenciáveis, conexas, sendo X fechada (n+1)-dimensional e Y sem bordo n-dimensional. Quando o domínio é a esfera e g é constante, consideramos homomorfismos w\' e w\'\' que juntos determinam o invariante de bordismo normal do par (f,g). Calculamos w\'\' para vários espaços e, em particular, para fibrados esféricos sobre esferas, obtemos que w\'\' é identicamente nulo se, e somente se, Y é trivial ou Y não é um S&#178-fibrado sobre S&#8308. Finalmente, obtemos resultados tipo Wecken quando X é a esfera, e quando X é o espaço projetivo real de dimensão 3 e Y é a esfera de dimensão 2. / In this work, we study coincidences between two maps f and g, from X to Y, where X and Y are smooth manifolds, connected, being X closed (n+1)-dimensional and Y without boundary n-dimensional. When the domain is the sphere and g is constant, we consider homomorphisms w\' and w\'\' which together determine the normal bordism invariant of the pair (f,g). We calculate w\'\' for several spaces and, in particular, for sphere bundles over spheres, we obtain that w\'\' is identically null if and only if Y is trivial or Y is not an S&#178-bundle over S&#8308. Finally, we obtain Wecken type results when X is the sphere, and when X is the 3-dimensional real projective space and Y is the 2-dimensional sphere.

Cette thèse explore les propriétés quantitatives et qualitatives des fibrés cotangents T∗M de variétés lisses fermées M, d’un point de vue symplectique. Les aspects quantitatifs concernent le problème d’empilement de boules symplectiques dans un voisinage ouvert W de la section nulle. Nous introduisons une fonction de type distance ρW sur la section nulle M en utilisant l’empilement symplectique de deux boules. Dans le cas où W est le fibré en disques unitaire associé à une métrique riemannienne g, nous montrons comment reconstruire la métrique g à partir de ρW. Comme étape intermédiaire, nous construisons un plongement symplectique de la boule B2n(2/√π) de capacité 4 dans le produit de disques unitaires lagrangiens Bn(1) × Bn(1). Une telle construction implique la conjecture de Viterbo forte pour Bn(1) × Bn(1). Nous donnons aussi une borne sur le rayon relatif de Gromov Gr(M, W) lorsque M admet une action non-contractile de S1. La borne est donnée en termes de l’action symplectique des relevés des orbites non-contractiles de l’action de S1. Nous donnons aussi des exemples de cas où cette borne est optimale. Ce résultat fait partie d’un travail en collaboration avec Dylan Cant. La deuxième partie du travail est liée aux aspects qualitatifs. Nous montrons l’existence d’orbites périodiques de systèmes hamiltoniens sur T∗M pour une grande classe d’hamiltoniens. Un autre aspect qualitatif est la preuve de la conjecture de la corde Arnol’d pour les sous-variétés legendriennes conormales dans le fibré en co-sphères S∗M. Cette partie de la thèse est un travail conjoint avec Dylan Cant et Egor Shelukhin. Nous montrons que pour une sous-variété fermée donnée N ⊂ M, il existe une corde de Reeb non-constante dans (S∗M,α) avec extrémités sur ΛN := ν∗N ∩S∗M, pour toute forme de contact α sur S∗M qui induit la structure de contact standard. / This dissertation explores the quantitative and qualitative properties of the cotangent bundles T ∗M of a closed smooth manifolds M , from the symplectic point of view. Quantitative aspects involve packing the open neighborhood W of the zero section with symplectic balls. We introduce a distance-like function ρW on the zero section M using the symplectic packing of two balls. In the case when W is the unit disc-cotangent bundle associated to the Riemannian metric g, we show how to recover the metric g from ρW . As an intermediate step, we construct a symplectic embedding from the ball B2n(2/√π) of capacity 4 to the product of Lagrangian unit discs Bn(1) × Bn(1). Such a construction implies the strong Viterbo conjecture for Bn(1) × Bn(1). We also give a bound on the relative Gromov width Gr(M, W) when M admits a non-contractible S1-action. The bound is given in terms of the symplectic action of the lift of non-contractible orbits of the S1-action. We also provide examples of when such a bound is sharp. This result is part of the joint work with Dylan Cant. The second part of this joint work is related to the qualitative aspects. We show the existence of periodic orbits of Hamiltonian systems on T ∗M for a large class of Hamiltonians. Another qualitative aspect is proof of the Arnol’d chord conjecture for conormal Legendrians in the co-sphere bundle S∗M . This part of the dissertation is joint work with Dylan Cant and Egor Shelukhin. We show that for a given closed submanifold N ⊂ M there exists a non-constant Reeb chord in (S∗M, α) with endpoints on ΛN := ν∗N ∩ S∗M, for arbitrary contact form α on S∗M which induces standard contact structure.

Betrachtet man das kartesische Produkt X × X eines topologischen Raumes X mit sich selbst, so kann auf diesem Objekt insbesondere die Involution betrachtet werden, die die Koordinaten vertauscht, die also (x,y) auf (y,x) abbildet. Das sogenannte 'Symmetrische Quadrieren' in Čech-Homologie mit Z/2-coefficients wurde von Schick et al. 2007 als Abbildung von der k-ten Čech-Homologiegruppe eines Raumes X in die 2k-te Čech-Homologiegruppe von X × X modulu der oben genannten Involution definiert. Es stellt sich heraus, dass diese Konstruktion entscheidend ist für den Beweis eines parametrisierten Borsuk-Ulam-Theorems.Das Symmetrische Quadrieren kann zu einer Abbildung in Bordismus verallgemeinert werden, was der Hauptgegenstand dieser Dissertation ist. Genauer gesagt werden wir zeigen, dass es eine wohldefinierte, natürliche Abbildung von der k-ten singulären Bordismusgruppe von X in die 2k-te Bordismusgruppe von X × X modulu der obigen Involution gibt.Insbesondere ist dieses Quadrieren wirklich eine Verallgemeinerung der Konstruktion in Čech-Homologie, denn es ist vertauschbar mit dem Übergang von Bordismus zu Homologie via dem Fundamentalklassenhomomorphismus. Auf dem Weg zu diesem Resultat wird das Konzept des Čech-Bordismus als Kombination aus Bordismus und Čech-Homologie zunächst definiert und dann mit Čech-Homologie verglichen.