Submitted by JÚLIO HEBER SILVA (julioheber@yahoo.com.br) on 2018-03-14T17:24:36Z No. of bitstreams: 2 Dissertação - Angie Tatiana Suárez Romero - 2018.pdf: 2209912 bytes, checksum: 0ad7489cc1457ed892d896b3aa2f4885 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2018-03-15T11:07:28Z (GMT) No. of bitstreams: 2 Dissertação - Angie Tatiana Suárez Romero - 2018.pdf: 2209912 bytes, checksum: 0ad7489cc1457ed892d896b3aa2f4885 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Made available in DSpace on 2018-03-15T11:07:28Z (GMT). No. of bitstreams: 2 Dissertação - Angie Tatiana Suárez Romero - 2018.pdf: 2209912 bytes, checksum: 0ad7489cc1457ed892d896b3aa2f4885 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2018-03-05 / Conselho Nacional de Pesquisa e Desenvolvimento Científico e Tecnológico - CNPq / Cayley’s theorem allows us to represent a finite group as a permutations group of a finite set of points. In general, an action of a finite group G in a finite set, is described as an application of the group G in the symmetric group Sym(Ω). In this work we will describe some algorithms for permutation groups and implement them in the GAP system. We begin by describing a way of representing groups in computers, we calculate orbits, stabilizers in the basic form and by means of Schreier’s vectors. Later we make algorithms to work with primitive and transitive groups, thus arriving at the concept of BSGS, base and strong generator set, for permutation groups with the algorithm SCHREIERSIMS. In the end we work with group homomorphisms, we find the elements of a group through backtrack searches. / O Teorema de Cayley nos permite representar um grupo finito como grupo de permutações de um conjunto finito de pontos. De forma geral, uma ação de um grupo finito G em um conjunto finito Ω, é descrita como uma aplicação do grupo G no grupo simétrico Sym(Ω). Neste trabalho vamos descrever alguns algoritmos para grupos de permutação e implementa-los no sistema GAP. Começamos descrevendo uma maneira de representar grupos em computadores, calculamos órbitas, estabilizadores na forma básica e por meio de vetores de Schreier. Posteriormente fazemos algoritmos para trabalhar com grupos transitivos e primitivos, chegando assim ao conceito de, base e conjunto gerador forte (BSGS) para grupos de permutação finitos com o algoritmo SCHREIER-SIMS. No final trabalhamos com homomorfismos de grupos e encontramos os elementos de um grupo mediante pesquisas backtrack.

[Formulae and special characters in this field can only be approximated. See PDF version for accurate reproduction] In this thesis we investigate the properties of k-closures of certain finite permutation groups. Given a permutation group G on a finite set Ω, for k ≥ 1, the k-closure G(k) of G is the largest subgroup of Sym(Ω) with the same orbits as G on the set Ωk of k-tuples from Ω. The first problem in this thesis is to study the 3-closures of affine permutation groups. In 1992, Praeger and Saxl showed if G is a finite primitive group and k ≥ 2 then either G(k) and G have the same socle or (G(k),G) is known. In the case where the socle of G is an elementary abelian group, so that G is a primitive group of affine transformations of a finite vector space, the fact that G(k) has the same socle as G gives little information about the relative sizes of the two groups G and G(k). In this thesis we use Aschbacher’s Theorem for subgroups of finite general linear groups to show that, if G ≤ AGL(d, p) is an affine permutation group which is not 3-transitive, then for any point α ∈ Ω, Gα and (G(3) ∩ AGL(d, p))α lie in the same Aschbacher class. Our results rely on a detailed analysis of the 2-closures of subgroups of general linear groups acting on non-zero vectors and are independent of the finite simple group classification. In addition, modifying the work of Praeger and Saxl in [47], we are able to give an explicit list of affine primitive permutation groups G for which G(3) is not affine. The second research problem is to give a partial positive answer to the so-called Polycirculant Conjecture, which states that every transitive 2-closed permutation group contains a semiregular element, that is, a permutation whose cycles all have the same length. This would imply that every vertex-transitive graph has a semiregular automorphism. In this thesis we make substantial progress on the Polycirculant Conjecture by proving that every vertex-transitive, locally-quasiprimitive graph has a semiregular automorphism. The main ingredient of the proof is the determination of all biquasiprimitive permutation groups with no semiregular elements. Publications arising from this thesis are [17, 54].