>Magister Scientiae - MSc / The pursuit of graphs which are vertex-transitive and non-Cayley on groups has been ongoing for some time. There has long been evidence to suggest that such graphs are a very rarety in occurrence. Much success has been had in this regard with various approaches being used. The aim of this thesis is to find such a class of graphs. We will take an algebraic approach. We will define Cayley graphs on loops, these loops necessarily not being groups. Specifically, we will define meta-Cayley graphs, which are vertex-transitive by construction. The loops in question are defined as the semi-direct product of groups, one of the groups being Z₂ consistently, the other being in the class of dihedral groups. In order to prove non-Cayleyness on groups, we will need to fully determine the automorphism groups of these graphs. Determining the automorphism groups is at the crux of the matter. Once these groups are determined, we may then apply Sabidussi's theorem. The theorem states that a graph is Cayley on groups if and only if its automorphism group contains a subgroup which acts regularly on its vertex set. / Chemicals Industries Education and Training Authority (CHIETA)

W. D. Munn proved that a finite dimensional representation of an inverse semigroup is equivalent to a ⋆-representation if and only if it is bounded. The first goal of this thesis will be to give new analytic proof that every finite dimensional representation of a compact inverse semigroup is equivalent to a ⋆-representation. The second goal is to parameterize all finite dimensional irreducible representations of a compact inverse semigroup in terms of maximal subgroups and order theoretic properties of the idempotent set. As a consequence, we obtain a new and simpler proof of the following theorem of Shneperman: a compact inverse semigroup has enough finite dimensional irreducible representations to separate points if and only if its idempotent set is totally disconnected. Our last theorem is the following: every norm continuous irreducible ∗-representation of a compact inverse semigroup on a Hilbert space is finite dimensional.

Renormalization procedures for families of dynamical systems have been used to prove many interesting results. Examples of results include that the bifurcation rate for the attractors of an analytic one-parameter family of quadratic-like maps is universal for all such families, unique ergodicity for almost every interval exchange mapping, a unique ergodicity criterion for the vertical translation flow of a flat surface in terms of its ``renormalization dynamics", known as Masur's criterion, and the classification of circle diffeomorphisms up to $C^{\infty}$ conjugation. We introduce renormalization procedures for $C^{*}$-algebras and étale groupoids using the concepts of $C_{0}(X)$-algebras and Morita equivalence for the former, and groupoid bundles and groupoid equivalence, in the sense of Muhly, Renault and Williams, for the latter. We focus on proving analogs to Masur's criterion in both cases using $C^{*}$-algebraic methods. Applying our criterion to our examples of renormalization procedures provides a unique trace criterion for unital AF algebras extending the one provided by Treviño in the setting of flat surfaces and the one provided by Veech in the setting of interval exchange mappings. Also, we recover the old fact that rotation of the circle by an irrational angle is uniquely ergodic, and the new fact that interesting groupoids associated to certain iterated function systems, recently introduced by Korfanty, have unique invariant probability measures whenever they are minimal. Lastly, we show how an étale groupoid renormalization procedure arises from an étale groupoid which factors down onto a groupoid associated to its renormalization dynamics, whenever it is a local homeomorphism. / Graduate

We address the problem of finding groupoid models for C*-algebras given some prescribed K-theory data. This is a reasonable question because a groupoid model for a C*-algebra reveals much about the structure of the algebra. A great deal of progress towards solving this problem has been made using constructions with inductive limits, subgroupoids, and dynamical systems. This dissertation approaches the question with a more specific methodology in mind, with factor groupoids. In the first part, we develop a portrait of relative K-theory for C*-algebras using the general framework of Banach categories and Banach functors due to Max Karoubi. The purpose of developing such a portrait is to provide a means of analyzing the K-theory of an inclusion of C*-algebras, or more generally of a *-homomorphism between two C*-algebras. Another portrait may be obtained using a mapping cone construction and standard techniques (it is shown that the two presentations are naturally and functorially isomorphic), but for many examples, including the ones considered in the second part, the portrait obtained by Karoubi's construction is more convenient. In the second part, we construct examples of factor groupoids and analyze their C*-algebras. A factor groupoid setup (two groupoids with a surjective groupoid homomorphism between them) induces an inclusion of two C*-algebras, and therefore the portrait of relative K-theory developed in the first part, together with an excision theorem, can be used to elucidate the structure. The factor groupoids are obtained as quotients of AF-groupoids and certain extensions of Cantor minimal systems using iterated function systems. We describe the K-theory in both cases, and in the first case we show that the K-theory of the resulting C*-algebras can be prescribed through the factor groupoids. / Graduate

In this thesis we present the deformation theory of Lie groupoid morphisms, Lie subgroupoids and symplectic groupoids. The corresponding deformation complexes governing such deformations are defined and used to investigate a Moser argument in each of these contexts. We also apply this theory to the case of Lie group morphisms and Lie subgroups, obtaining rigidity results of these structures. Moreover, in the case of symplectic groupoids, we define a map between the differentiable and deformation cohomology of the underlying groupoid, which is regarded as the global counterpart of a map $i$ defined by Crainic and Moerdijk (2004) which relates the (Poisson) cohomology of the Poisson structure on the base $M$ of the groupoid to the deformation cohomology of the Lie algebroid $T^{*}M$ associated to it. / Nesta tese apresentamos a teoria de deformação de morfismos de grupoides de Lie, subgrupoides de Lie e grupoides simpléticos, definimos os correspondentes complexos de deformação que controlam as deformações destas estruturas, e usamos estes complexos para desenvolver o argumento de Moser em cada um destes contextos. Também aplicamos esta teoria ao caso de morfismos de grupos de Lie e subgrupos de Lie obtendo resultados de rigidez de tais estruturas. Ademais, no caso de grupoides simpléticos, definimos uma função entre a cohomologia diferenciável e a cohomologia de deformação do grupoide, que é interpretada como o análogo global da aplicação $i$ definida por Crainic e Moerdijk (2004) que relaciona a cohomologia de Poisson da estrutura de Poisson induzida na base $M$ do grupoide com a cohomologia de deformação do algebroide de Lie $T^{*}M$ associado à estrutura de Poisson.

This licentiate thesis consists of one paper about unitary representationtheory of ample groupoids and semigroups together with generalizationsto étale and non-Hausdorff groupoids. In the paper we study algebraically the type I and CCR properties forample Hausdorff groupoids. Clarke and Van Wyk proved that both ofthese properties admit a topological characterization for Hausdorff second countable groupoids in terms of separation properties of their orbitspace and the isotropy groups. Using a Stone type duality between ample groupoids and Boolean inverse semigroups with meets, we exploit thischaracterization to get a purely algebraic statement. We also apply thoseresults to get characterizations of the type I and CCR properties for inverse semigroups using their Boolean inverse completions. The generalization is about characterizing the same properties for both étale and ample non-necessarily Hausdorff groupoids which nonethelesshave Hausdorff unit spaces. In this setup, we first give a direct proofof the topological characterization for the CCR property which doesn't rely on the disintegration theory. The argument cannot be adapted toget an easier proof in the type I case, but we rather explain how to geta proof following the original ideas of Clark and Van Wyk in that case.Finally, we state for both étale and ample groupoids algebraic conditionsequivalent to the CCR and GCR properties on their pseudogroup of openand compact open bisections respectively.

Neste trabalho, abordamos o conceito de simetria em teoria de campos, no âmbito hamiltoniano mais precisamente, sua relação com leis de conservação, conforme estabelecida pelo(s) teorema(s) de Noether. Propomos uma visão alternativa àquela normalmente usada na literatura, baseada na substituição de grupos e álgebras de Lie por grupoides e algebroides de Lie. Tradicionalmente, dado um fibrado E de configuração sobre o espaço-tempo M (cujas seções são os campos do modelo sob investigação), simetrias são implementadas pela ação de um grupo de automorfismos de E, ou seja, um subgrupo de Aut(E), no espaço &#915 (E) das seções de E, exigindo-se que o funcional ação S seja invariante sob tal ação: neste caso, quando o pertinente subgrupo for de dimensão infinita, surgem graves dificuldades quando queremos tratar de questões de análise e de geometria com rigor matemático. A vantagem principal desta abordagem alternativa provém do fato de que, embora o grupo Aut(E) e, tipicamente, os subgrupos relevantes, assim como o espaço &#915 (E), sejam de dimensão infinita, a sua ação é induzida por uma ação de um grupoide de Lie no fibrado pertinente, a qual envolve apenas variedades de dimensão finita e portanto não há qualquer dúvida em relação a questões tais como qual seria a topologia ou estrutura de variedade subjacente ou em qual sentido essa ação deve ser suave. Formulamos o teorema de Noether neste contexto, baseado em uma nova versão da construção da aplicação momento que a cada gerador de simetrias que associa uma (n - 1)-forma sobre J*E cujo pull-back com uma seção de J* E, que é solução das equações de movimento, produz uma (n - 1)-forma sobre o espaço-tempo, a famosa corrente de Noether, que é conservada, ou seja, fechada / In this thesis, we deal with the concept of symmetry in field theory, in the covariant hamiltonian approach more precisely, its relation with conservation laws, as established by Noethers theorem(s). We propose an alternative view to that normally used in the literature, based on replacing Lie groups and algebras by Lie groupoids and algebroids. Traditionally, given a configuration bundle E over space-time M (whose sections are the fields of the model under investigation), symmetries are implemented by the action of a group of automorphisms of E, i.e., a subgroup of Aut(E), on the space &#915 (E) of sections of E, requiring the action functional S to be invariant under that action: in this case, when the pertinent subgroup has infinite dimension, serious difficulties arise when we want to deal with analytical and geometrical questions with mathematical rigor. The main advantage of this alternative approach comes from the fact that, although the group Aut(E) and, typically, the relevant subgroups, as well as the space &#915 (E), are infinite-dimensional, its action is induced by the action of a Lie groupoid in the pertinent bundle, which involves only finite-dimentional manifolds and therefore there is no doubt about questions such as what should be the topology or the underlying manifold structure or in what sense this action should be smooth. We formulate the Noethers theorem in this context, based on a new version of the construction of the momentum map that associates a (n - 1)-form on J*E to each symmetries generator whose pull-back with a section of J*E, that is solution of the equations of motion, produces a (n - 1)-form on the space-time, the famous Noether current, that is conserved, i.e., closed

Neste trabalho, abordamos o conceito de simetria em teoria de campos, no âmbito hamiltoniano mais precisamente, sua relação com leis de conservação, conforme estabelecida pelo(s) teorema(s) de Noether. Propomos uma visão alternativa àquela normalmente usada na literatura, baseada na substituição de grupos e álgebras de Lie por grupoides e algebroides de Lie. Tradicionalmente, dado um fibrado E de configuração sobre o espaço-tempo M (cujas seções são os campos do modelo sob investigação), simetrias são implementadas pela ação de um grupo de automorfismos de E, ou seja, um subgrupo de Aut(E), no espaço &#915 (E) das seções de E, exigindo-se que o funcional ação S seja invariante sob tal ação: neste caso, quando o pertinente subgrupo for de dimensão infinita, surgem graves dificuldades quando queremos tratar de questões de análise e de geometria com rigor matemático. A vantagem principal desta abordagem alternativa provém do fato de que, embora o grupo Aut(E) e, tipicamente, os subgrupos relevantes, assim como o espaço &#915 (E), sejam de dimensão infinita, a sua ação é induzida por uma ação de um grupoide de Lie no fibrado pertinente, a qual envolve apenas variedades de dimensão finita e portanto não há qualquer dúvida em relação a questões tais como qual seria a topologia ou estrutura de variedade subjacente ou em qual sentido essa ação deve ser suave. Formulamos o teorema de Noether neste contexto, baseado em uma nova versão da construção da aplicação momento que a cada gerador de simetrias que associa uma (n - 1)-forma sobre J*E cujo pull-back com uma seção de J* E, que é solução das equações de movimento, produz uma (n - 1)-forma sobre o espaço-tempo, a famosa corrente de Noether, que é conservada, ou seja, fechada / In this thesis, we deal with the concept of symmetry in field theory, in the covariant hamiltonian approach more precisely, its relation with conservation laws, as established by Noethers theorem(s). We propose an alternative view to that normally used in the literature, based on replacing Lie groups and algebras by Lie groupoids and algebroids. Traditionally, given a configuration bundle E over space-time M (whose sections are the fields of the model under investigation), symmetries are implemented by the action of a group of automorphisms of E, i.e., a subgroup of Aut(E), on the space &#915 (E) of sections of E, requiring the action functional S to be invariant under that action: in this case, when the pertinent subgroup has infinite dimension, serious difficulties arise when we want to deal with analytical and geometrical questions with mathematical rigor. The main advantage of this alternative approach comes from the fact that, although the group Aut(E) and, typically, the relevant subgroups, as well as the space &#915 (E), are infinite-dimensional, its action is induced by the action of a Lie groupoid in the pertinent bundle, which involves only finite-dimentional manifolds and therefore there is no doubt about questions such as what should be the topology or the underlying manifold structure or in what sense this action should be smooth. We formulate the Noethers theorem in this context, based on a new version of the construction of the momentum map that associates a (n - 1)-form on J*E to each symmetries generator whose pull-back with a section of J*E, that is solution of the equations of motion, produces a (n - 1)-form on the space-time, the famous Noether current, that is conserved, i.e., closed

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Já é bem estabelecido na geometria diferencial o uso de fibrados principais com grupo de estru- tura para a definição e o estudo de algumas estruturas geométricas na base do fibrado. O uso de fibrados principais com grupoide de estrutura na definição de estruturas geométricas sobre varieda- des não tem sido muito explorada. O único exemplo do uso desses fibrados para definir estruturas geométricas foi dado Haefliger. Ele mostrou que folheações regulares sobre uma variedade estão em correspondência com uma classe de fibrados principais com grupoide de estrutura, e usando a classificação de fibrados principais ele obtive a classificação de folheações regulares a menos de homotopia sobre uma variedade aberta. Neste trabalho propomos uma definição a qual generaliza as folheações regulares para produzir uma classe de fibrados vetoriais ancorados e provamos para eles um teorema de classificação no espirito do teorema de Haefliger. Depois aplicamos a teoria desenvolvida aos grupoides com formas multiplicativas e mostramos como a nossa definição per- mite trasladar a geometria guardada na forma multiplicativa para a base do fibrado principal. Em seguida voltamos para o caso de folheações regulares e mostramos que a nossa proposta permite incluir novas estruturas transversais à folheação. / It is well know in differencial geometry the use of principal bundles with structure group to define and study some geometric structures on the base of the bundle. The use of principal bun- dle with a structure groupoid has not been extensively studied yet. The only example using this kind of bundle was provided by Haefliger in his study of regular foliations. Haefliger showed that regular foliations can be identified with some class of principal bundles with structure groupoid, then by using the classifying theorem of principal bundles he arrived to the classification theorem of regular foliations up to homotopy on open manifolds. In this work we will propose a definition that generalizes regular foliations to include anchored vector bundles and, will prove a classification theorem for these structures in the spirit of Haefligers theorem. Then we will apply this theory to groupoids with multiplicative forms and show that our definition permits to transfer the geometry encoded in the multiplicative form to the base of the bundle. Then we will back to the case of regular foliations and show that our proposal allow new transversal structures to the foliation.