This thesis is about extended affine Lie algebras and extended affine Weyl groups. In Chapter I, we provide the basic knowledge necessary for the study of extended affine Lie algebras and related objects. In Chapter II, we show that the well-known twisting phenomena which appears in the realization of the twisted affine Lie algebras can be extended to the class of extended affine Lie algebras, in the sense that some extended affine Lie algebras (in particular nonsimply laced extended affine Lie algebras) can be realized as fixed point subalgebras of some other extended affine Lie algebras (in particular simply laced extended affine Lie algebras) relative to some finite order automorphism. We show that extended affine Lie algebras of type A₁, B, C and BC can be realized as twisted subalgebras of types A_§¤(l ¡Ã 2) and D algebras. Also we show that extended affine Lie algebras of type BC can be realized as twisted subalgebras of type C algebras. In Chapter III, the last chapter, we study the Weyl groups of reduced extended affine root systems. We start by describing the extended affine Weyl group as a semidirect product of a finite Weyl group and a Heisenberg-like normal subgroup. This provides a unique expression for the Weyl group elements which in turn leads to a presentation of the Weyl group, called a presentation by conjugation. Using a new notion, called the index, which is an invariant of the extended affine root systems, we show that one of the important features of finite and affine root systems (related to Weyl group) holds for the class of extended affine root systems. We also show that extended affine Weyl groups (of index zero) are homomorphic images of some indefinite Weyl groups where the homomorphism and its kernel are given explicitly.

Let G be a finite group and A be a subgroup of Aut(G). In this work, we studied the influence of the index of fixed point subgroup of A in G on the structure of G. When A is cyclic, we proved the following: (1) [G,A] is solvable if this index is squarefree and the orders of G and A are coprime. (2) G is solvable if the index of the centralizer of each x in H-G is squarefree where H denotes the semidirect product of G by A. Moreover, for an arbitrary subgroup A of Aut(G) whose order is coprime to the order of G, we showed that when G is solvable, then the Fitting length f([G,A]) of [G,A] is bounded above by the number of primes (counted with multiplicities) dividing the index of fixed point subgroup of A in G and this bound is best possible.

This thesis arose from a desire to better understand the structures of automorphism groups and inner automorphism groups of quandles. We compute and give the structure of the automorphism groups of all dihedral quandles. In their paper Matrices and Finite Quandles, Ho and Nelson found all quandles (up to isomorphism) of orders 3, 4, and 5 and determined their automorphism groups. Here we find the automorphism groups of all quandles of orders 6 and 7. There are, up to isomoprhism, 73 quandles of order 6 and 289 quandles of order 7.

<p>&nbsp / </p> <p align="left">The groups we consider in this study belong to the class <font face="F30">X</font><font face="F25" size="1"><font face="F25" size="1">0 </font></font><font face="F15">of all finitely generated groups with finite commutator subgroups.</font></p>

A group G is called an FC-group if the conjugacy class of every element is finite. G is called a minimal non-FC-group if G is not an FC-group, but every proper subgroup of G is an FC-group. The first part of this thesis is on minimal non-FC-groups and their finitary permutational representations. Belyaev proved in 1998 that, every perfect locally finite minimal non-FC-group has non-trivial finitary permutational representation. In Chapter 3, we write the proof of Belyaev in detail. Recall that a group G is called quasi-simple if G is perfect and G/Z(G) is simple. The second part of this thesis is on finite quasi-simple groups and their coprime automorphisms. In Chapter 4, the result of Parker and Quick is written in detail: Namely / if Q is a quasi-simple group and A is a non-trivial group of coprime automorphisms of Q satisfying |Q: C_{Q}(A)| &lt / n then |Q| &lt / n3, that is |Q| is bounded by a function of n.

Magister Scientiae - MSc / The groups we consider in this study belong to the class X0 of all nitely generated groups with nite commutator subgroups. We shall eventually narrow down to the groups of the form T owZn for some n 2 N and some nite abelian group T. For a X0-group H, we study the non-cancellation set, (H), which is de ned to be the set of all isomorphism classes of groups K such that H Z = K Z. For X0-groups H, on (H) there is an abelian group structure [38], de ned in terms of embeddings of K into H, for groups K of which the isomorphism classes belong to (H). If H is a nilpotent X0-group, then the group (H) is the same as the Hilton-Mislin (see [10]) genus group G(H) of H. A number of calculations of such Hilton-Mislin genus groups can be found in the literature, and in particular there is a very nice calculation in article [11] of Hilton and Scevenels. The main aim of this thesis is to compute non-cancellation (or genus) groups of special types of X0-groups such as mentioned above. The groups in question can in fact be considered to be direct products of metacyclic groups, very much as in [11]. We shall make extensive use of the methods developed in [30] and employ computer algebra packages to compute determinants of endomorphisms of nite groups. / South Africa

The polynomial maps whose Jacobian determinant is equal to 1 are called Keller maps. The Keller Jacobian conjecture claims that every Kellermap is injective. This conjecture is true for polynomials whose degree is less than or equal to two. In this paper we prove that the general casereduces to the study of the injectivity of maps of the form z 7! z+H(z),where the nonzero components of H are homogeneous polynomials of degree three, and every Jacobian matrix DH(z) is nilpotent. / A las aplicaciones polinomiales con el determinante de su matriz jacobiana igual a 1 se las llama aplicaciones de Keller. Segun la conjetura jacobiana de Keller, cada aplicacion de Keller es inyectiva. Tal conjetura es verdadera para las aplicaciones polinomiales de grado menor o igual a dos. En el presente trabajo tambien se muestra que el caso general se reduce a estudiar la inyectividad de aplicaciones de la forma z 7! z +H(z); donde las componentes no nulas de H son polinomios homogéneos de grado tres y cada matriz Jacobiana DH(z) es nilpotente.

CoordenaÃÃo de AperfeÃoamento de Pessoal de NÃvel Superior / As assinaturas digitais sÃo de fundamental importÃncia para as comunicaÃÃes eletrÃnicas no mundo todo por garantirem a integridade e autenticidade da informaÃÃo. Com os avanÃos da ciÃncia nas Ãreas da mecÃnica quÃntica e a introduÃÃo destes novos conceitos nas telecomunicaÃÃes, a seguranÃa da informaÃÃo tambÃm precisou evoluir e cada vez mais se tem buscado novos sistemas de seguranÃa que forneÃam maior integridade e autenticidade que os sistemas clÃssicos. Dessa forma o objetivo deste trabalho à utilizar as propriedades do problema QSCDff , para a criaÃÃo de um protocolo de assinatura quÃntica de mensagens. O problema QSCD ff possui propriedades matemÃticas e computacionais para garantir a integridade e autenticidade das assinaturas geradas. O protocolo proposto faz uso de chaves descritas na forma de estados quÃnticos construÃdos a partir de permutaÃÃes de um grupo simÃtrico e de uma funÃÃo de hash para a compressÃo da mensagem original. Como entrada o protocolo recebe a mensagem clÃssica e uma chave privada. Para a geraÃÃo do estado quÃntico da assinatura utiliza-se uma permutaÃÃo como chave privada e o hash da mensagem. Gerar tal assinatura sem ter uma chave privada consiste em resolver um problema de encontrar automorfismos nÃo triviais de grafos. A validaÃÃo deste estado à feita atravÃs da aplicaÃÃo do algoritmo quÃntico de busca de Grover. Por fim à mostrado que a probabilidade de falsificaÃÃo da assinatura à negligenciÃvel dado o nÃmero de cÃpias do estado da assinatura.

Orientadores: Marcelo Firer, Luiz Antonio Barrera San Martin / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Matematica, Estatistica e Computação Cientifica / Made available in DSpace on 2018-08-05T23:33:46Z (GMT). No. of bitstreams: 1 Talpo_HumbertoLuiz_D.pdf: 1408389 bytes, checksum: b11f884cbf1e05f81138a8e91a5980dc (MD5) Previous issue date: 2006 / Resumo: Seja G uma árvore homogênea e Aut(G) seu grupo de automorfismos. Um automorfismo f Î Aut(G) é par se d(f(x),x) º0 mod 2 para todo vértice x Î G, onde d(.,.) é a função distância definida pelo comprimento do menor caminho ligando os vértices. O conjunto Aut+(G) de todos os automorfismos pares é um subgrupo de índice 2 em Aut(G). Definimos uma geodésica g Ì G como um subgrafo isomorfo a Z (onde Z é visto como um grafo que possui arestas unindo inteiros consecutivos). Uma reflexão em uma geodésica g é um automorfismo involutivo f (f² =1) tal que f(x) = x se, e somente se, x Î G. Denotamos por R o conjunto de todas as reflexões em geodésicas. Neste trabalho (Capítulo 2) provamos que, dada uma árvore homogênea de grau par G, o número de cobertura de Aut+(G) pelas reflexões em geodésicas é 11, no seguinte sentido: dado f Î Aut+(G) existem f1, f2,... fk com k £ 11, tais que f(x) = fk °fk-1°...°f1(x) para todo vértice x em G. Além disso, considerando árvores homogêneas, sabemos que o grupo de automorfismos é completo e o subgrupo de automorfismos pares é simples. Flexibilizamos a condição de homogeneidade e conseguimos demonstrar (Capítulo 3) para o caso de árvores semi-homogêneas, que o grupo de automorfismos é simples e completo / Abstract: Let G be a homogeneous tree and Aut(G) its group of automorphism. An automorphism Î Aut(G) is said to be even if d(f(x),x) º0 mod 2 for every vertex x Î G of , where d(.,.) is the canonical distance function defined by the minimum length of paths connecting the vertices. The set Aut+(G) of all even automorphism is a subgroup of index 2 in Aut(G). We define a geodesic g Ì G as a subtree isomorphic to the standard tree of the integers Z, that is, a homogeneous subtree of degree 2. A reflection in a geodesic g is an involutive automorphism f (f² =1) such that f(x) = x if x Î G. We denote by R the set of all reflections in geodesics. In this work (Chapter 2) we prove that, for every even degree tree G, the covering number of Aut+(G) by reflections in geodesics is 11, in the sense that give f Î Aut+(G) there are f1, f2,... fk with k £ 11, such that f(x) = fk °fk-1°...°f1(x) for every vertex x in G.Moreover, if we consider homogeneous trees we know that automorphisms group is complete and the even automorphisms subgroup is simple. We vary the homogeneous condition and we prove that (Chapter 3) for the semi-homogeneous trees, the automorphisms group is simple and complete / Doutorado / Doutor em Matemática

Dentre todos os sistemas dinâmicos os sistemas Anosov têm atraído a atenção de muitos matemáticos. No caso de fluxo Anosov em uma variedade fechada M de dimensão três, Sérgio Fenley definiu o conceito de losangos no recobrimento universal de M e obteve resultados importantes envolvendo losangos e automorfismos do recobrimento universal. Seguindo o que foi feito por Fenley, e utilizando o conceito de losangos no espaço das órbitas do fluxo levantado (no recobrimento universal), Thierry Barbot obteve condições suficientes para que um toro incompressível numa 3-variedade fechada suportando um fluxo Anosov seja isotópico a um outro que é transverso ao fluxo. Neste trabalho consideramos ações Anosov de \'R POT. k\' sobre uma variedade fechada M de dimensão k + 2. Primeiramente, conseguimos resultados análogos aos de Fenley (sobre existência de losangos) para estas ações, e usando isso, finalmente obtemos condições suficientes para que um toro incompressível seja isotópico a um toro transverso à ação. Este último resultado é uma generalização de Barbot mencionado acima / Among all dynamical systems the Anosov systems has attracted the attention of many mathematicians. In the case of an Anosov flow in a closed manifold M of dimension three, Sérgio Fenley defined the concept of lozenges in the universal covering of M and obtained important results involving lozenges and covering automorphism. Following what was made by Fenley, and using the concept of lozenge on the orbit space of the lifted flow (in the universal covering). Thierry Barbot obtains sufficient conditions for an incompressible torus in a closed 3-manifold supporting an Anosov flow to be isotopic to another which is transverse to flow. If this work we considered Anosov of \'R POT. k\' on a closed manifold M of dimension k + 2. First, we obtain analogous results those of Fenley (about existence of lozenges) for this actions, and using this, finally we obtain sufficient conditions for an incompressible torus to be isotopic to another torus which is transverse to action. This last result is a generalization of Barbot\'s result mentioned above