Abstract The dissertation consists of three articles in which the solvability of groups and the solvability of loops are considered. The first parts of the thesis survey some basic information and results on transversals and loops. The summarizing parts provide the three main results for the solvability of groups and loops.

Seja Ω ⊂ ℝ2 aberto contendo a origem. Denotando as variáveis por (x,t), provamos a resolubilidade local, em um disco D aberto centrado na origem, D ⊂ Ω, de equações semilineares da forma Pu = f(x,t,u); onde P = ∂t + a(x,t)∂x, a ∈ C2 (Ω), Im ≠ 0 e f ∈ C2 (Ω × ℂ), usando o princípio da contração; P = ∂t - itk∂x, k: número inteiro positivo par e f ∈ C∞(ℝ2 × ℂ), usando o teorema da resolubilidade local de Hounie e Santiago. / Let Ω be an open set of ℝ2 containing the origin. Using the variables (x,t), we prove the local solvability, on an open ball D centered at the origin, D ⊂ Ω, of semilinear equations of the form Pu = f(x,t,u); where P = ∂t + a(x,t)∂x, a ∈ C2 (Ω), Im ≠ 0 and f ∈ C2 (Ω × ℂ), using the principle of contracting mappings; P = ∂t - itk∂x, k: even positive integer number and f ∈ C∞(ℝ2 × ℂ), using the local solvability theorem of Hounie and Santiago.

Seja Ω ⊂ ℝ2 aberto contendo a origem. Denotando as variáveis por (x,t), provamos a resolubilidade local, em um disco D aberto centrado na origem, D ⊂ Ω, de equações semilineares da forma Pu = f(x,t,u); onde P = ∂t + a(x,t)∂x, a ∈ C2 (Ω), Im ≠ 0 e f ∈ C2 (Ω × ℂ), usando o princípio da contração; P = ∂t - itk∂x, k: número inteiro positivo par e f ∈ C∞(ℝ2 × ℂ), usando o teorema da resolubilidade local de Hounie e Santiago. / Let Ω be an open set of ℝ2 containing the origin. Using the variables (x,t), we prove the local solvability, on an open ball D centered at the origin, D ⊂ Ω, of semilinear equations of the form Pu = f(x,t,u); where P = ∂t + a(x,t)∂x, a ∈ C2 (Ω), Im ≠ 0 and f ∈ C2 (Ω × ℂ), using the principle of contracting mappings; P = ∂t - itk∂x, k: even positive integer number and f ∈ C∞(ℝ2 × ℂ), using the local solvability theorem of Hounie and Santiago.

Neste trabalho estudamos a resolubilidade suave de campos vetoriais complexos suaves da forma L = L1 + iL2, em uma variedade M, com as seguintes propriedades: em cada ponto de M, os campos L1 e L2 são linearmente independentes , e seu colchete [L1, L2](x) é uma combinação linear de L1(x) e L2(x). Para tratar da resolubilidade local, nos utilizamos da teoria dos espaços Bp,k e operadores de força constante. Seguindo para a resolubilidade semiglobal, estudamos a folheação gerada por L1 e L2: mostramos que neste caso as folhas possuem estrutura de variedade complexa, o que nos permite obter um panorama bastante completo sobre o problema. Para encerrar, provamos que L é globalmente resolúvel se e somente se for semiglobalmente resolúvel e M for L-convexa; exibimos condições suficientes para que isto ocorra. / In this work we shall study the smooth solvability of smooth complex vector fields L = L1 + iL2 on a smooth manifold M, assuming the following properties: for any point of M, L1 and L2 are linearly independent and [L1,L2] is a linear combination of L1 and L2. Discussing local solvability, we shall employ the theory of Bp,k Spaces and Operators of Constant Strength. Moving on to Semi-Global Solvability, we shall study the foliation that is generated by L1 and L2: we prove that in this case the leaves are actually complex manifolds, which allow us to obtain an wide comprehension of the problem. Finally, we show that L is globally solvable if and only if it is semi-globally solvable and M is L-convex; we then exhibit sufficient conditions in order to it occur.

Neste trabalho estudamos a resolubilidade suave de campos vetoriais complexos suaves da forma L = L1 + iL2, em uma variedade M, com as seguintes propriedades: em cada ponto de M, os campos L1 e L2 são linearmente independentes , e seu colchete [L1, L2](x) é uma combinação linear de L1(x) e L2(x). Para tratar da resolubilidade local, nos utilizamos da teoria dos espaços Bp,k e operadores de força constante. Seguindo para a resolubilidade semiglobal, estudamos a folheação gerada por L1 e L2: mostramos que neste caso as folhas possuem estrutura de variedade complexa, o que nos permite obter um panorama bastante completo sobre o problema. Para encerrar, provamos que L é globalmente resolúvel se e somente se for semiglobalmente resolúvel e M for L-convexa; exibimos condições suficientes para que isto ocorra. / In this work we shall study the smooth solvability of smooth complex vector fields L = L1 + iL2 on a smooth manifold M, assuming the following properties: for any point of M, L1 and L2 are linearly independent and [L1,L2] is a linear combination of L1 and L2. Discussing local solvability, we shall employ the theory of Bp,k Spaces and Operators of Constant Strength. Moving on to Semi-Global Solvability, we shall study the foliation that is generated by L1 and L2: we prove that in this case the leaves are actually complex manifolds, which allow us to obtain an wide comprehension of the problem. Finally, we show that L is globally solvable if and only if it is semi-globally solvable and M is L-convex; we then exhibit sufficient conditions in order to it occur.

In the thesis we investigate the connections between arbitrary functions and their realizing polynomials over finite algebras. We study functionally complete algebras, i.e. algebras over which every function can be realized by a polynomial expression. We characterize functional completeness by the so called Stone-Weierstrass property, and we determine the functionally complete semigroups and semirings. Then we investigate the computational perspective of the function-polynomial relationships over finite groups. We consider the efficient representability, the equivalence, and the equation solvability problems. We approach the efficient representability problem from three directions. We consider the length of functions, we investigate the circuit complexity of functions, and we analyse the finite-state sequential machine representation of Boolean functions. From each of these viewpoints we give bounds on the potential efficiency of computations based on functionally complete groups compared to computations based on the two-element Boolean algebra. Neither the equivalence problem nor the equation solvability problem has been completely characterized for finite groups. The complexity of the equivalence problem was only known for nilpotent groups. In the thesis we determine the complexity of the equivalence problem for certain meta-Abelian groups and for all non-solvable groups. The complexity of the equation solvability problem is known for nilpotent groups and for non-solvable groups. There are no results about the complexity of the equation solvability problem for solvable non-nilpotent groups apart from the case of certain meta-cyclic groups that we present in the thesis. Moreover, we determine the complexity of the equation solvability problem for all functionally complete algebra. The idea of the extended equivalence problem emerges from the observation that the commutator might significantly change the length of group-polynomials. We characterize the complexity of the extended equivalence problem for finite groups. For many finite groups we determine the complexity of the equivalence problem if the commutator is considered as the basic operation of the group.

A essência desta tese são resultados e aplicações da teoria de operadores de ordem infinita. A ideia central deste trabalho é um teorema de representação de ultradistribuições a partir de operadores ultradiferenciais agindo em funções Gevrey. Essa representação junto com a regularidade do kernel destes operadores nos permite importar uma dada propriedade válida para funções Gevrey para o contexto de ultradistribuições e vice-versa. Aproveitamos estes teoremas para aprender um pouco mais sobre a resolubilidade local de complexos induzidos por estruturas localmente integráveis. Definimos três conceitos de resolubilidade local destes complexos no ambiente Gevrey e provamos a equivalência entre eles. Para tanto, foi necessário estudar espaços de funções Gevrey com respeito a uma dada estrutura hipo-analítica e investigar quando este novo espaço é isomorfo ao usual. E isto nos permitiu entender melhor a ação dos operadores considerados e o papel por eles desempenhado nesta teoria. / The essence of this thesis are results and applications of the theory of infinite order operators. The central idea of this work is a representation theorem of ultradistributions by ultradifferential operators acting on Gevrey functions. This representation together with the regularity of the kernel of these operators allow us to import a given property from Gevrey functions to the ultradistribution context and vice versa. We took advantage of these theorems to learn a little more about the local solvability of the complexes induced by locally integrable structures. We defined three concepts of local solvability of these complexes in the Gevrey environment and we proved that they are equivalent. To do so, it was necessary to study the space of the Gevrey functions with respect to a given hypo-analytic structure and to investigate when this new space is isomorphic to the usual one. And this allowed us to better understand the action of the considered operators and their role in this theory.

A essência desta tese são resultados e aplicações da teoria de operadores de ordem infinita. A ideia central deste trabalho é um teorema de representação de ultradistribuições a partir de operadores ultradiferenciais agindo em funções Gevrey. Essa representação junto com a regularidade do kernel destes operadores nos permite importar uma dada propriedade válida para funções Gevrey para o contexto de ultradistribuições e vice-versa. Aproveitamos estes teoremas para aprender um pouco mais sobre a resolubilidade local de complexos induzidos por estruturas localmente integráveis. Definimos três conceitos de resolubilidade local destes complexos no ambiente Gevrey e provamos a equivalência entre eles. Para tanto, foi necessário estudar espaços de funções Gevrey com respeito a uma dada estrutura hipo-analítica e investigar quando este novo espaço é isomorfo ao usual. E isto nos permitiu entender melhor a ação dos operadores considerados e o papel por eles desempenhado nesta teoria. / The essence of this thesis are results and applications of the theory of infinite order operators. The central idea of this work is a representation theorem of ultradistributions by ultradifferential operators acting on Gevrey functions. This representation together with the regularity of the kernel of these operators allow us to import a given property from Gevrey functions to the ultradistribution context and vice versa. We took advantage of these theorems to learn a little more about the local solvability of the complexes induced by locally integrable structures. We defined three concepts of local solvability of these complexes in the Gevrey environment and we proved that they are equivalent. To do so, it was necessary to study the space of the Gevrey functions with respect to a given hypo-analytic structure and to investigate when this new space is isomorphic to the usual one. And this allowed us to better understand the action of the considered operators and their role in this theory.

In Part I of the thesis an account is given of the basic algebra of extension fields which is required for the understanding of Galois theory. The fundamental theorem states the relationships of the subgroups of a permutation group of the root field of an equation to the subfields which are left invariant by these subgroups. Extensions of the basic theorem conclude Part I. In part II the solvability of equations by radicals is discussed, for fields of characteristic zero. A discussion of finite fields and primitive roots leads to a criterion for the solvability by radicals of equations over fields of prime characteristic. Finally, a method for determining the Galois group of any equation is discussed. Most of the material in the introductory chapters is taken from Artin's: Galois Theory (cf. p. 120). / Thesis / Master of Arts (MA)

This work explores the unsolvability of the general quintic equation through the lens of Galois theory. We begin by providing a historical perspective on the problem. This starts with the solution of the general cubic equation derived by Italian mathematicians. We then move on to Lagrange's insights on the importance of studying the permutations of roots. Finally, we discuss the critical contributions of Évariste Galois, who connected the solvability of polynomials to the properties of permutation groups. Central to our thesis is the introduction and motivation of key concepts such as fields, solvable groups, Galois groups, Galois extensions, and radical extensions. We rigorously develop the theory that connects the solvability of a polynomial to the solvability of its Galois group. After developing this theoretical framework, we go on to show that there exist quintic polynomials with Galois groups that are isomorphic to the symmetric group S5. Given that S5 is not a solvable group, we establish that the general quintic polynomial is not solvable by radicals. Our work aims to provide a comprehensive and intuitive understanding of the deep connections between polynomial equations and abstract algebra.