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In this thesis, we present the Weil representation over loop symplectic groups. Then we study the question of whether or not the Schrodinger representation and the Weil representation are continuous. Finally, we define a cocycle of the rank 2 symplectic group, adapt Kubota's theorem to this case and verify that it splits over a subgroup.

Quandles are distributive algebraic structures that were introduced by David Joyce [24] in his Ph.D. dissertation in 1979 and at the same time in separate work by Matveev [34]. Quandles can be used to construct invariants of the knots in the 3-dimensional space and knotted surfaces in 4-dimensional space. Quandles can also be studied on their own right as any non-associative algebraic structures. In this dissertation, we introduce f-quandles which are a generalization of usual quandles. In the first part of this dissertation, we present the definitions of f-quandles together with examples, and properties. Also, we provide a method of producing a new f-quandle from a given f-quandle together with a given homomorphism. Extensions of f-quandles with both dynamical and constant cocycles theory are discussed. In Chapter 4, we provide cohomology theory of f-quandles in Theorem 4.1.1 and briefly discuss the relationship between Knot Theory and f-quandles. In the second part of this dissertation, we provide generalized 2,3, and 4- cocycles for Alexander f-quandles with a few examples. Considering “Hom-algebraic Structures” as our nutrient enriched soil, we planted “quandle” seeds to get f-quandles. Over the last couple of years, this f- quandle plant grew into a tree. We believe this tree will continue to grow into a larger tree that will provide future fruit and contributions.

L'invariant de Casson est un invariant classique des 3-sphères d'homologie entière. Via les scindements de Heegaard, S. Morita le décrit comme la somme de deux homomorphismes d et q définis sur un sous-groupe K_(g,1) du groupe de difféotopies M_(g,1) d'une surface S_(g,1) orientée de genre g à une composante de bord. L'homomorphisme d constitue le "Coeur de l'invariant de Casson" et est décrit géométriquement en termes de SU-parallélisations de Morita des mapping tores. A l'origine, d provient d'une application d_X définie sur M_(g,1) comme la différence entre le cocycle de Meyer et un cocycle d'intersection dépendant d'un champ de vecteurs X sur la surface S_(g,1). Tout d'abord, nous revisiterons les résultats de Morita et rendrons l'application d_X calculatoire. Puis nous considèrerons les cobordismes d'homologie et leur groupe associé H_(g,1) : via les mapping cylindres, M_(g,1) constitue un sous-groupe de H_(g,1). Dans la perspective de prolonger d, nous étendrons les cocycles d'intersection et cocycle de Meyer aux cobordismes d'homologie munis de structure d'Euler.

In this thesis we study the application of trace maps over Galois fields and Galois rings in the construction of non-binary linear and non-linear codes and mutually unbiased bases. Properties of the trace map over the Galois fields and Galois rings has been used very successfully in the construction of cocyclic Hadamard, complex Hadamard and Butson Hadamard matrices and consequently to construct linear codes over integers modulo prime and prime powers. These results provide motivation to extend this work to construct codes over integers modulo . The prime factorization of integers paved the way to focus our attention on the direct product of Galois rings and Galois fields of the same degree. We define a new map over the direct product of Galois rings and Galois fields by using the usual trace maps. We study the fundamental properties of the this map and notice that these are very similar to that of the trace map over Galois rings and Galois fields. As such this map called the trace-like map and is used to construct cocyclic Butson Hadamard matrices and consequently to construct linear codes over integers modulo . We notice that the codes construct in this way over the integers modulo 6 is simplex code of type . A further generalization of the trace-like map called the weighted-trace map is defined over the direct product of Galois rings and Galois fields of different degrees. We use the weighted-trace map to construct some non-linear codes and mutually unbiased bases of odd integer dimensions. Further more we study the distribution of over the Galois fields of degree 2 and use it to construct 2-dimensional, two-weight, self-orthogonal codes and constant weight codes over integers modulo prime.

Cette thèse est consacrée à l'étude des propriétés ergodiques du feuilletage horosphérique d'une variété géométriquement finie à courbure négative $M$. Un de nos principaux résultats est la classification des mesures transverses quasi-invariantes dont la dérivée de Radon-Nikodym est un cocycle höldérien fixé, associé à une mesure de Gibbs. À un tel cocycle, nous associons certaines moyennes sur les horosphères et montrons qu'elles s'équidistribuent vers la mesure de Gibbs correspondante lorsque $M$ est compacte ou convexe-cocompacte. Lorsqu'elle n'est ni compacte ni convexe-cocompacte, nous limitons l'étude aux moyennes associées à la mesure d'entropie maximale. Nous montrons qu'elles forment une suite tendue, ce qui, dans le cas des surfaces, nous permet d'obtenir leur équidistribution vers cette mesure d'entropie maximale. En corollaire, nous obtenons l'équidistribution des orbites du flot horocyclique d'une surface hyperbolique géométriquement finie mais de volume infini.

Given an action of a countable group with a quasi-invariant measure, there exists a multiplicative group in (0, ∞), called the ratio set of the group action, which in a sense describes the values of the Radon-Nikodym derivative. The main purpose of this thesis is to find the ratio set of the action of a finitely generated free group Ƒ on its topological boundary ∂Ƒ (the set of infinite words) for a certain natural class of quasi-invariant boundary measures. -- In Section 1, we focus on the general ergodic theory of equivalence relations. We outline the set-up, borrow from [1], [4] the definitions of the central notions of the theory, including counting measures (Proposition 1.8), quasi-invariance (Definition 1.6), Radon-Nikodym cocycle (Definition 1.15) and raio set (Definition 1.19), and illustrate them on the example of the orbit equivalence relation of a Markov shift (Definition 1.22). We also introduce the principal object: the boundary action of a finitely generated free group (see Section 1.2). -- In Section 2, we define the class of multiplicative Markov measures (Definition 2.1). These are the measures on a topological Markov chain entirely determined just by an initial (base) distribution and the admissibility matrix; the transition probabilities are then just the normalized restrictions of the base distribution onto the set of admissible transitions (see [7]). In the case of the free group, its boundary has a natural structure of a topological Markov chain (determined by the irreducibility condition from the definition of a free group: consecutive letters should not cancel each other), and in this case, we show that the multiplicative Markov measures are precisely the ones for which the Radon-Nikodym cocycle is a product cocycle (i.e. a cocycle whose potential only depends on the first letter of the input; see Definition 2.8). The final result of this section is an explicit description of the ratio set of the boundary action with respect to multiplicative Markov measures. -- In Section 3, given a probability measure 𝜇 on the set of free generators and their inverses, the definition of the associated nearest neighbor random walk is given. According to Furstenberg's Theorem (proof provided in Appendix), in this random walk, sample paths converge almost surely to a random boundary point, and the resulting limit distribution on the boundary of the free group is called the harmonic measure of the random walk (see Section 3.1). We show that the harmonic measure is a multiplicative measure (Theorem 3.3), and therefore the results of Section 2 allow us to describe the ratio set of the harmonic measure (Theorem 3.5). A significant role in these considerations is played by the passage probabilities of the random walk (given a group element, the probability that it is ever visited by a random walk). Since the harmonic measure is multiplicative, its potential only depends on the first letter, and this dependence actually amounts to taking the inverse of the corresponding passage probability (Proposition 2.9, Remark 2.10). Finally, we establish a one-to-one correspondence between three families of numbers indexed by the alphabet of the free group and subject to natural conditions; these are the step distributions of the random walk, the base of the harmonic measure (which is multiplicative Markov) and the family of passage probabilities (Theorem 3.6). -- In Section 4, we discuss another method for finding the ratio set of the harmonic measure based on using Martin theory (see [2]). -- In the Appendix, we prove Furstenberg's Theorem, a result used for defining the harmonic measure in Section 3. Actually, it is applicable not only for the nearest neighbor random walk (i.e. not only when the probability measure 𝜇 is supported on the alphabet set) but also the more general case where the support of the step distribution generates the free group. Moreover, in addition to the existence it also characterizes the harmonic measure as the unique 𝜇-stationary measure on the boundary

Ce travail de thèse porte sur la dynamique du flot linéaire des surfaces de translation et de sa renormalisation par le flot de Teichmüller introduite par H. Masur et W. Veech en 1982. Une version combinatoire de cette renormalisation, l'induction de Rauzy sur les échanges d'intervalles, fût introduite auparavant par G. Rauzy en 1979. D'une part, nous faisons une étude combinatoire des classes de Rauzy qui forment une partition de l'ensemble des permutations irréductibles et interviennent dans l'algorithme d'induction de Rauzy. Nous donnons une formule pour la cardinalité de chaque classe. D'autre part, nous étudions un modèle de billard infini périodique dans le plan appelé le "vent dans les arbres" introduit dans une version stochastique par P. et T. Ehrenfest en 1912 et par J. Hardy et J. Weber en 1980 dans la version périodique. Nous construisons une famille de directions pour lesquelles le flot du billard est divergent donnant ainsi des exemples de Z^2-cocycles divergents au-dessus d'échanges d'intervalles. De plus, nous démontrons que le taux polynomial de diffusion générique est 2/3 autrement dit que la distance maximale atteinte par une particule au temps t est de l'ordre de t^2/3. / In this thesis, we study the dynamics of the linear flow of translation surfaces and its renormalization by the Teichmüller flow introduced by H. Masur and W. Veech in 1982. A combinatorial version of the renormalization, the Rauzy induction on interval exchange transformations, was introduced by G. Rauzy in 1979. First of all, we consider the combinatorics of Rauzy classes which form a partition of the set of irreducible permutations and are part of the Rauzy induction. In a second time, we consider an infinite Z^2-periodic billiard in the plane called the wind-tree model. It was introduced in a stochastic version by P. and T. Ehrenfest in 1912 and in the periodic version by J. Hardy and J. Weber in 1980. We construct a family of directions for which the flow of the billiard is divergent and hence give examples of divergent Z^2-cocycles over interval exchange transformations. Moreover, we prove that the polynomial rate of diffusion is generically 2/3. In other words, the maximal distance reached by a particule below time t has the order of t^2/3.

Neste trabalho nós encontramos condições suficientes para que dois homeomorfismos do círculo, f e g, \'C POT. 2+\' por pedaços serem \'C POT. 1\' conjugados. Além de restrições sobre a combinatória dessas aplicações (nós assumimos que elas tem algum tipo de combinatória limitada) e uma condição necessária sobre as derivadas laterais nos pontos onde f e g não são diferenciáveis, nós também assumimos que a não-linearidade média de f e g é zero. A prova é baseada no estudo detalhado da renormalização de transformações de intercâmbio de intervalos generalizadas de genus um com certas restrições combinatoriais / In this work we find sufficient conditions for two piecewise \'C POT. 2+\' homeomorphisms f and g of the circle to be \'C POT. 1\' conjugate. Besides the restrictions on the combinatorics of the maps (we assume that the maps have the same bounded combinatorics) and necessary conditions on the one-side derivatives of points where f and g are not differentiable, we also assume zero mean nonlinearity for f and g. The proof relies on the detailed study of the renormalizations of genus one generalized interval exchange maps with certain restrictions on their combinatorics

Neste trabalho nós encontramos condições suficientes para que dois homeomorfismos do círculo, f e g, \'C POT. 2+\' por pedaços serem \'C POT. 1\' conjugados. Além de restrições sobre a combinatória dessas aplicações (nós assumimos que elas tem algum tipo de combinatória limitada) e uma condição necessária sobre as derivadas laterais nos pontos onde f e g não são diferenciáveis, nós também assumimos que a não-linearidade média de f e g é zero. A prova é baseada no estudo detalhado da renormalização de transformações de intercâmbio de intervalos generalizadas de genus um com certas restrições combinatoriais / In this work we find sufficient conditions for two piecewise \'C POT. 2+\' homeomorphisms f and g of the circle to be \'C POT. 1\' conjugate. Besides the restrictions on the combinatorics of the maps (we assume that the maps have the same bounded combinatorics) and necessary conditions on the one-side derivatives of points where f and g are not differentiable, we also assume zero mean nonlinearity for f and g. The proof relies on the detailed study of the renormalizations of genus one generalized interval exchange maps with certain restrictions on their combinatorics