Thesis (PhD)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: See full text. / AFRIKAANSE OPSOMMING: Sien volteks.

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The representation theory of infinite dimensional groups is in its infancy. This paper is an attempt to apply the orbit method to a particular infinite dimensional group, the spin extension of the restricted unitary group. Our main contribution is in showing that various homogeneous spaces for this group admit measures which can be used to realize the unitary structure for the standard modules.

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A thesis submitted to the faculty of Science, University of the Witwatersrand, in fulfilment of the requirements for the degree of Doctor of Philosophy, / The inverse problem in the Calculus of Variations involves determining the Lagrangians, if any, associated with a given (system of) differential equation(s). One can classify Lagrangians according to the Lie algebra of symmetries of the Action integral (the Noether algebra). We give a complete classification of first-order Lagrangians defined on the line and produce results pertaining to the dimensionality of the algebra of Noether symmetries and compare and contrast these with similar results on the algebra of Lie symmetries of the corresponding Euler-Lagrange .equations. It is proved that the maximum dimension of the Noether point symmetry algebra of a particle Lagrangian. is five whereas it is known that the maximum dimension Qf the Lie algebra of the corresponding scalar second-order Euler-Lagrange equation is eight. Moreover, we show th'a.t a particle Lagrangian does not admit a maximal four-dimensional Noether point symmeiry algebra and consequently a particle Lagrangian admits the maximal r E {O, 1,2,3, 5}-dimensional Noether point symmetry algebra, It is well .known that an important means of analyzing differential equations lies in the knowledge of the first integrals of the equation. We deliver an algorithm for finding first integrals of partial differential equations and show how some of the symmetry properties of the first integrals help to 'further' reduce the order of the equations and sometimes completely solve the equations. Finally, we discuss some open questions. These include the inverse problem and classification of partial differential equations. ALo, there is the question of the extension of the results to 'higher' dimensions. / Andrew Chakane 2018

Orientador: Carina Alves / Banca: Marta Cilene Gadotti / Banca: Cintya Wink de Oliveira Benedito / Resumo: Este trabalho aborda conceitos básicos de Álgebra Linear e suas aplicações no desenvolvimento da Teoria de Códigos Corretores de Erros. O uso desta ferramenta matemática simpli ca a geração e a decodi cação dos códigos lineares. Destacamos também a importância de se trabalhar com este tema na educação básica / Abstract: The present work addresses basic concepts of Linear Algebra and its applications in the development of the Theory of Error Correcting Codes. The use of this mathematical tool simpli es the generation and decoding of linear codes. This dissertation also highlights the importance of working with this subject in high school / Mestre

An integral domain D is weakly integrally closed if whenever there is an element x in the quotient field of D and a nonzero finitely generated ideal J of D such that xJ J2, then x is in D. We define weakly integrally closed numerical monoids similarly. If a monoid algebra is weakly integrally closed, then so is the monoid. A pattern F of finitely many 0's and 1's is forbidden if whenever the characteristic binary string of a numerical monoid M contains F, then M is not weakly integrally closed. Any stretch of the pattern 11011 is forbidden. A numerical monoid M is weakly integrally closed if and only if it has a forbidden pattern. For every finite set S of forbidden patterns, there exists a monoid that is not weakly integrally closed and that contains no stretch of a pattern in S. It is shown that particular monoid algebras are weakly integrally closed. / by Mary E. Hopkins. / Thesis (Ph.D.)--Florida Atlantic University, 2009. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2009. Mode of access: World Wide Web.

A conjectura de Makar-Limanov arma que se um anel de divisão D e finitamente gerado e de dimensão infinita sobre seu centro k, então D contém uma k-subálgebra livre de posto 2. Neste trabalho, investigaremos a existência de tais estruturas no anel de divisão de frações do anel de polinômios skew L[t; \'\\sigma\' ], onde t é uma variável e \'\\sigma\' é um k-automorfismo de L. Mais especificamente, assumindo o que chamamos de Hipótese do Delta 3.3.1, provaremos esse resultado para L / k uma extensão de corpos, mesmo quando L não é finitamente gerado sobre k. Finalmente, provaremos a Hipótese do Delta e a conjectura, quando L é o corpo de funções de uma variedade abeliana ou o corpo de funções do espaço projetivo n-dimensional / Makar-Limanov\'s conjecture states that if a division ring D is finitely generated and infinite dimensional over its center k then D contains a free k-subalgebra of rank 2. In this work, we will investigate the existence of such structures in the division ring of fractions of the skew polynomial ring L[t; \'\\sigma\' ], where t is a variable and \'\\sigma\' is an k-automorphism of L. More specifically, assuming what we called Delta\'s Hipothesis 3.3.1, we prove this result for L / k a field extension, even when L isn\'t finitely generated over k. Finally, we prove Delta\'s Hipothesis and the conjecture when either L is the function field of an abelian variety or the function field of the n-dimensional projective space

São estudados alguns aspectos das álgebras alternativas, como o bar-radical de uma álgebra bárica alternativa e as identidades de grau 4 e 5 nas álgebras de Cayley-Dickson. Neste estudo fazemos uso da decomposição de Peirce e de diversas propriedades importantes das álgebras alternativas. Concluímos mostrando que as únicas identidades de grau 4 são as triviais e as de grau 5 são conseqüência de outras duas identidades conhecidas / We studied some aspects of alternative algebras, in special the bar radical of an alternative baric algebra and identities of degree 4 and 5 of Cayley-Dickson algebras. We made significant use of the Peirce decomposition and several properties of the alternative algebras, in order to show that the only identities of degree four are the trivial ones, and the identities of degree five are consequences of other two known identities.