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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

A brief survey of self-dual codes

Oktavia, Rini 2009 August 1900 (has links)
This report is a survey of self-dual binary codes. We present the fundamental MacWilliams identity and Gleason’s theorem on self-dual binary codes. We also examine the upper bound of minimum weights of self-dual binary codes using the extremal weight enumerator formula. We describe the shadow code of a self-dual code and the restrictions of the weight enumerator of the shadow code. Then using the restrictions, we calculate the weight enumerators of self-dual codes of length 38 and 40 and we obtain the known weight enumerators of this lengths. Finally, we investigate the Gaborit-Otmani experimental construction of selfdual binary codes. This construction involves a fixed orthogonal matrix, and we compare the result to the results obtained using other orthogonal matrices. / text
2

Self-dual metrics on toric 4-manifolds : extending the Joyce construction

Griffiths, Hugh Norman January 2009 (has links)
Toric geometry studies manifolds M2n acted on effectively by a torus of half their dimension, Tn. Joyce shows that for such a 4-manifold sufficient conditions for a conformal class of metrics on the free part of the action to be self-dual can be given by a pair of linear ODEs and gives criteria for a metric in this class to extend to the degenerate orbits. Joyce and Calderbank-Pedersen use this result to find representatives which are scalar flat K¨ahler and self-dual Einstein respectively. We review some results concerning the topology of toric manifolds and the construction of Joyce metrics. We then extend this construction to give explicit complete scalar-flat K¨ahler and self-dual Einstein metrics on manifolds of infinite topological type, and to find a new family of Joyce metrics on open submanifolds of toric spaces. We then give two applications of these extensions — first, to give a large family of scalar flat K¨ahler perturbations of the Ooguri-Vafa metric, and second to search for a toric scalar flat K¨ahler metric on a neighbourhood of the origin in C2 whose restriction to an annulus on the degenerate hyperboloid {(z1, z2)|z1z2 = 0} is the cusp metric.
3

A compact expression for periodic instantons

Cherkis, Sergey A., O’Hara, Clare, Zaitsev, Dmitri 12 1900 (has links)
Instantons on various spaces can be constructed via a generalization of the Fourier transform called the ADHM-Nahm transform. An explicit use of this construction, however, involves rather tedious calculations. Here we derive a simple formula for instantons on a space with one periodic direction. It simplifies the ADHM-Nahm machinery and can be generalized to other spaces.
4

Sobre a existência ou não de bases normais auto-duais para extensões galoisianas de corpos / About the existence or not of self-dual normal bases for finite galosian extensions of fields

Coutinho, Sávio da Silva 20 March 2009 (has links)
Neste trabalho, apresentamos um estudo sobre a existência ou não de bases normais auto-duais para extensões galoisianas finitas de corpos, mostrando que toda extensão galoisiana finita de grau ímpar posui uma base normal auto-dual, enquanto que para extensões galoisianas de grau par, apresentamos algumas condições suficientes que garantem a não existência de bases normais auto-duais / In this work, we present a study about the existence or not of self-dual normal bases for finite galoisian extensions of fields, showing that all the odd degree finite galoisian extension has a self-dual normal base, whereas for even degree galoisian extensions, we present some sufficient conditions that assure the non-existence of self-dual normal bases
5

Two theorems on Galois representations and Shimura varieties

Karnataki, Aditya Chandrashekhar 12 August 2016 (has links)
One of the central themes of modern Number Theory is to study properties of Galois and automorphic representations and connections between them. In our dissertation, we describe two different projects that study properties of these objects. In our first project, which is analytic in nature, we consider Artin representations of Q of dimension 3 that are self-dual. We show that these occur with density 0 when counted using the conductor. This provides evidence that self-dual representations should be rare in all dimensions. Our second project, which is more algebraic in nature, is related to automorphic representations. We show the existence of canonical models for certain unitary Shimura varieties. This should help us in computing certain cohomology groups of these varieties, in which regular algebraic automorphic representations having useful properties should be found.
6

Sobre a existência ou não de bases normais auto-duais para extensões galoisianas de corpos / About the existence or not of self-dual normal bases for finite galosian extensions of fields

Sávio da Silva Coutinho 20 March 2009 (has links)
Neste trabalho, apresentamos um estudo sobre a existência ou não de bases normais auto-duais para extensões galoisianas finitas de corpos, mostrando que toda extensão galoisiana finita de grau ímpar posui uma base normal auto-dual, enquanto que para extensões galoisianas de grau par, apresentamos algumas condições suficientes que garantem a não existência de bases normais auto-duais / In this work, we present a study about the existence or not of self-dual normal bases for finite galoisian extensions of fields, showing that all the odd degree finite galoisian extension has a self-dual normal base, whereas for even degree galoisian extensions, we present some sufficient conditions that assure the non-existence of self-dual normal bases
7

Estudos sobre Teorias com Chern-Simons: Equivalência entre Modelos e Efeito Aharonov-Bohm Não-Abeliano / Studies on theories with Chern-Simons: equivalence between models and Aharonov-Bohm effect is not abelian.

Malacarne, Luís Carlos 02 March 1999 (has links)
O objetivo desta tese é estudar alguns modelos contendo o termo de Chern-Simons, cuja presença induz várias características tais como massa topológica e spin fracionário. Iniciamos tratando o problema da equivalência entre os modelos Auto-Dual minimamente acoplado com o campo de Dirac, e o modelo de Maxwell-Chern-Simons com um acoplamento magnético com férmions. Nós mostramos que os setores fermiônicos dos modelos somente são equivalentes se adicionarmos uma auto-interação tipo Thirring. Em seguida, analisamos o efeito Aharonov-Bohm não-Abeliano para partículas de spin 0 e ½. Partindo da teoria quântica de campos relativística no gauge de Coulomb e usando o procedimento do corte intermediário, para separar o momento de integração nas regiões de baixa e alta energia, nós obtemos o limite não relativístico dos modelos. Desta forma as correções radiativas, tais como polarização do vácuo e correção de vértice, são automaticamente incluídas. Finalizando estudamos algumas / The aim of this work is to study some models with Chern-Simons term~ which induces several properties such as l-opological mass and fractional spin. We start studying the exact equivalence between the Self-Dual model minimally coupled to a Dirac field and the Maxwell-Chern-Simons model witb non-minimal magnetic coupling to fermions. Weshow that the fermions sectors of the models are equivalent only if a Thirring like interaction is included. Next we analyze the non-Abelian Aharonov-Bohm scattering for 0 and 1/2 spin particles. Starting Crom the relatistic quantum field theory and using 8 Coulomb gauge rormalism the one loop renorrnalizalion is implemented. Trough the introduction of na intermediaf) cutoff, separating the regions of high and low integration momentum the nonrelativistic Umit is derived. In this approach CJuant.um field theory vacuum polarization and anomalous magnetic momentum are automatically incorporated. Va also study some properties of the chat\'ged one spin particles interacting wit.h Chern Simons field.
8

Estudos sobre Teorias com Chern-Simons: Equivalência entre Modelos e Efeito Aharonov-Bohm Não-Abeliano / Studies on theories with Chern-Simons: equivalence between models and Aharonov-Bohm effect is not abelian.

Luís Carlos Malacarne 02 March 1999 (has links)
O objetivo desta tese é estudar alguns modelos contendo o termo de Chern-Simons, cuja presença induz várias características tais como massa topológica e spin fracionário. Iniciamos tratando o problema da equivalência entre os modelos Auto-Dual minimamente acoplado com o campo de Dirac, e o modelo de Maxwell-Chern-Simons com um acoplamento magnético com férmions. Nós mostramos que os setores fermiônicos dos modelos somente são equivalentes se adicionarmos uma auto-interação tipo Thirring. Em seguida, analisamos o efeito Aharonov-Bohm não-Abeliano para partículas de spin 0 e ½. Partindo da teoria quântica de campos relativística no gauge de Coulomb e usando o procedimento do corte intermediário, para separar o momento de integração nas regiões de baixa e alta energia, nós obtemos o limite não relativístico dos modelos. Desta forma as correções radiativas, tais como polarização do vácuo e correção de vértice, são automaticamente incluídas. Finalizando estudamos algumas / The aim of this work is to study some models with Chern-Simons term~ which induces several properties such as l-opological mass and fractional spin. We start studying the exact equivalence between the Self-Dual model minimally coupled to a Dirac field and the Maxwell-Chern-Simons model witb non-minimal magnetic coupling to fermions. Weshow that the fermions sectors of the models are equivalent only if a Thirring like interaction is included. Next we analyze the non-Abelian Aharonov-Bohm scattering for 0 and 1/2 spin particles. Starting Crom the relatistic quantum field theory and using 8 Coulomb gauge rormalism the one loop renorrnalizalion is implemented. Trough the introduction of na intermediaf) cutoff, separating the regions of high and low integration momentum the nonrelativistic Umit is derived. In this approach CJuant.um field theory vacuum polarization and anomalous magnetic momentum are automatically incorporated. Va also study some properties of the chat\'ged one spin particles interacting wit.h Chern Simons field.
9

Alternativní způsob řešení úloh LP / Alternative Method of Solution for LP Problem

Hanzlík, Tomáš January 2009 (has links)
Linear programming (LP) stands for an optimization of a linear objective function, subject to linear and non-negativity constraints. For this purpose many methods for LP emerged. The best known is Simplex Method. Another group of methods for LP is represented by Interior Point Methods (IPM). These methods are based on interior points of feasible region of a problem, while Simplex Method uses basic feasible solution of a problem. This thesis focuses on theoretical background of IPM and brings it into relation with algorithms based on IPM. KKT system and its significance are included and the algorithm solving Linear Complementarity Problem is discussed as well. In this thesis, two algorithms based on IPM are introduced and used for solving a sample LP problem.
10

Teorias duais massivas de spin-3/2 em D=2+1 / Massive spin-3/2 dual theories in D=2+1

Lima, Diego Sá de 05 February 2018 (has links)
Submitted by Diego Sa de Lima null (diegos.lima88@hotmail.com) on 2018-03-03T04:54:32Z No. of bitstreams: 1 Dissertacao_Teorias_duais_massivas_spin32.pdf: 569707 bytes, checksum: 2062a40c0ffdddb4c5801a33f1f13f9d (MD5) / Approved for entry into archive by Pamella Benevides Gonçalves null (pamella@feg.unesp.br) on 2018-03-05T18:32:28Z (GMT) No. of bitstreams: 1 lima_ds_me_guara.pdf: 569707 bytes, checksum: 2062a40c0ffdddb4c5801a33f1f13f9d (MD5) / Made available in DSpace on 2018-03-05T18:32:28Z (GMT). No. of bitstreams: 1 lima_ds_me_guara.pdf: 569707 bytes, checksum: 2062a40c0ffdddb4c5801a33f1f13f9d (MD5) Previous issue date: 2018-02-05 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Nesta dissertação serão analisados os dois modelos conhecidos na literatura que descrevem partículas massivas de spin 3/2 em D=2+1 dimensões. Essa análise será feita, assim como nos trabalhos relacionados aos bósons (spin 1, spin 2 e spin 3), via procedimento de Imersão de Calibre de Noether (ICN), Solda generalizada, análise de vínculos e condições de Fierz-Pauli. Através de argumentos de simetria, via ICN, apresentaremos uma forma de relacionar os dois modelos e mostraremos que é possível construir um novo modelo de terceira ordem em derivadas. Apresentaremos um modelo de dubleto de segunda ordem em derivadas de onde é possível obter os demais modelos auto-duais da teoria. A partir da aplicação da ICN no modelo de dubleto construiremos um novo modelo, de quarta ordem em derivadas, análogo a versão linearizada da chamada " New Massive Gravity". / In this master's thesis we will analyze the two known models in the literature wich describe massive spin 3/2 particles in D = 2 + 1 dimensions. This analysis will be done, as was previously done on works related to the bosons (spin- 1 , spin- 2 and spin- 3 ), via Noether gauge embedment (NGE) procedure, generalized soldering, hamiltonian constraints analysis and Fierz-Pauli conditions. Through symmetry arguments, by NGE, we will present a way of relating the two models and show that it is possible to construct a new model in third order derivatives. We will show a second order derivative doublet-model whence it is possible to obtain the other self-dual models of the theory. From the application of NGE in the dublet model we will construct a new model, wich has a fourth-order derivative term, analogue to the linearized version of the so-called "New Massive Gravity"

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