Submitted by Maria Aparecida (cidazen@gmail.com) on 2017-12-04T14:44:31Z No. of bitstreams: 1 João Andrade..pdf: 3163183 bytes, checksum: 0c7d19f31b8e570d13e85b371ea43554 (MD5) / Made available in DSpace on 2017-12-04T14:44:31Z (GMT). No. of bitstreams: 1 João Andrade..pdf: 3163183 bytes, checksum: 0c7d19f31b8e570d13e85b371ea43554 (MD5) Previous issue date: 2017-02-22 / CAPES. / For the recent years, there has been a growing interest in Lorentz-violating theories. Studies have been carried out addressing the inclusion of Lorentz-violating terms into the Standard Model (SM). This has led to the development of the Standard Model Extension (SME), which is a framework containing modifications that are power-counting renormalizable and consistent with the gauge structure of the SM. More recently, a nonminimal version of the SME was developed for the photon, neutrino, and fermion sector additionally including higher-derivative terms. One of the new properties of this nonminimal version is the lost of renormalizability. In this work, we study the main aspects of a modified Dirac theory in the nonminimal Standard-Model Extension. We focus on two types of operators namely, pseudovector and two-tensor operators. These two operators display an unusual property; they break the degeneracy of spin. This new property becomes manifest in providing two di erent dispersion relations, one for each spin projection. To solve the Dirac equation modified by those operators, we introduce a new method that was suggested by Kostelecký and Mewes in a recent research paper. This method allows to block-diagonalizing the modified Dirac equation and, thus, permits us to obtain the spinors. The objectives of the current work are as follows. First, we will review the main concepts for understanding the SME. Second, we will introduce how to extend the minimal fermion sector to the nonminimal one. Third, we will describe the method that block-diagonalizes the modified Dirac equation and we will compute the field equations. And,finally, we will get the exact dispersion relations and the spinor solutions for operators of arbitrary mass dimension. / Nos últimos anos, houve um aumento significativo no interesse em teorias que violam a simetria de Lorentz. Estudos têm sido realizados na tentativa de incluir termos que violam a simetria de Lorentz no Modelo Padrão (MP). Esta tentativa culminou no surgimento do chamado Modelo Padrão Estendido (MPE). Este modelo contempla todas as possíveis modificações que são consistentes com as propriedades já bem estabelecidas, tais como renormalizabilidade e a estrutura de gauge do MP. Mais recentemente, uma versão não-mínima do MPE foi desenvolvida para os setores dos fótons, neutrinos e para os férmions. Esta versão não-mínima caracteriza-se pela presença de altas derivadas. Uma das novas propriedades nesta versão não-mínima é a perda da renormalizabilidade. Neste trabalho, estudamos os principais aspectos da teoria de Dirac modi cada no MPE não-mínimo. Nós nos concentramos em dois tipos de operadores a saber, operadores pseudovetoriais e tensoriais. Estes dois operadores exibem uma propriedade incomum, eles quebram a degenerescência de spin. Esta nova propriedade manifesta-se, por exemplo, na presença de duas relações de dispersão diferentes, uma para cada projeção do spin. Para resolver a equação de Dirac modi cada por esses operadores, introduzimos um novo método que foi sugerido por Kostelecký e Mewes em um trabalho recente. Este método permite bloco-diagonalizar a equação de Dirac modi cada e, assim, nos fornece uma nova maneira de obter os espinores. Os objetivos do presente trabalho são os seguintes. Primeiro, iremos rever alguns conceitos essenciais para o entendimento do MPE. Segundo, apresentaremos a extens ão do setor fermiônico mínimo para o não-mínimo. Terceiro, descreveremos o método que bloco-diagonaliza a equação de Dirac modi cada e calcularemos as equações de campo. Por fim, calcularemos as relações de dispersão exatas e as soluções espinoriais para cada configuração não-mínima dos operadores citados.

On étudie l'opérateur de Dirac bidimensionnel avec un champ magnétique tendant vers l'infini en l'infini. Le spectre d'un tel opérateur est uniquement composé de valeurs propres et en particulier le spectre essentiel est réduit à un point. Pour un champ magnétique à croissance polynomiale, on donne l'équivalent des valeurs propres à l'infini.<br />Quand on perturbe cet opérateur par un potentiel électrique tendant vers zéro à l'infini avec une décroissance polynomiale, exponentielle ou à support compact, des valeurs propres sont créées près du point du spectre essentiel. On étudie le comportement asymptotique du spectre discret de l'opérateur perturbé près de ce point.<br />Pour l'opérateur de Dirac tridimensionnel avec un champ magnétique constant, on définit les résonances à l'aide de la méthode de dilatation analytique. Grâce à la méthode de Grushin, on étudie les résonances près des niveaux de Landau-Dirac à l'aide d'un hamiltonien effectif.

No description available.

<p>In this work, we apply $L^2$-index theory to compute the index of a non-Fredholm elliptic operator. The operator arises in Type I' string theory, and the index is found to be non-zero, thus implying existence of bound states.</p> / Dissertation

Thèse doctorat : Mathématiques : Nancy 1 : 2006. / Titre provenant de l'écran-titre.

Not available / text

Nonlinear Dirac equations exhibiting soliton phenomena are studied. Conditions are derived for the existence of solitons and an analysis of their stability is presented. New results are obtained for models previously considered in the literature. A particular model is studied for which all stationary states are localized in a finite domain and have positive energy but indefinite charge. The electromagnetic field is introduced by minimal coupling and it is shown that the discrete nature of the electric charge, and of the angular momentum, follow from a many-body stability principle. This principle also implies the de Broglie frequency relation, and furnishes an expression for the fine structure constant. The resulting charged soliton is tentatively identified with the electron.

Finding the distribution of a statistic is always an important problem that we face in statistical inference. Methods that are usually used for solving this problem are change of variable technique, distribution function technique and moment generating function technique. Among these methods change of variable technique is the most commonly used one. This method is simple when the statistic is a one-to-one transformation of the sample observations and if it is many-to-one, then one needs to compute the jacobian for each partition of the range for which the transformation is one-to-one. In addition, if we want to find the distribution of a statistic involving n random variables using the change of variable technique, we have to define (n-1) auxiliary variables. Unless these (n-1) auxiliary variables are carefully chosen, calculation of jacobian as well as finding the range of integration to obtain the marginal distribution of the statistic of interest become complicated. [See [3]]Au, Chi and Tam, Judy [1] proposed an alternative method of finding the distribution of a statistic by using Dirac generalized function. In this study we considera number of problems involving different probability distributions that are not quiet easy to solve by change of variable technique. We will illustrate the method by solving problems which include finding the distributions of sums, products, differences and ratios of random variables. The main purpose of the thesis is to show that using Dirac generalized function one can solve these problems with more ease. This alternative approach would be more suitable for students with limited mathematical background. / Department of Mathematical Sciences

Zugl.: München, Univ., Diss., 2008

Mannheim, Univ., Diss., 2003.