Orientador: Alvaro de Souza Dutra / Banca: José Abdalla Helayel Neto / Banca: Elbert Einstein Nehrer Macau / Resumo: Esta dissertacão tem como objetivo principal entender mais profundamente as mais variadas nuances do aparecimento de caos em sistemas de teoria de campos, além de um estudo sobre o comportamento das soluções solitônicas desses sistemas. Apresentamos um método, baseado na estrutura de m¶³nimos de potenciais, a ¯m de obter informações concretas sobre o comportamento das soluções solitônicas destes potenciais. Vericamos ainda a existência de novas soluções topologicas para um modelo que ¶e aplicado na descrição dos chamados twis- tons. Essas soluções possuem a particularidade de serem degeneradas, assim, para quebrar essa degenerescência, adicionamos ao potencial inicial um termo perturbativo. Determinamos também, novas soluções topologicas para uma lagrangiana contendo um campo escalar complexo, estudada por Trullinger e Subbaswamy em (Trullinger, S. E.; Subbaswamy, K. R. Physical Review A 19 (1979) 1340.) e por fim, aplicamos o método da seção de Poincare neste modelo verificando suas regioes caóticas. / Abstract: The main objective of this work is a deeper comprehension about the different kinds of the appearing of chaos in field theory's systems, besides the study about the behavior of these soliton solutions systems. We present a method, based on the structure of potential's minima, to get information about the behavior of the solitons solutions. We calculate new topological solutions for a model that was applied to the description of the so called twistons. These solutions are degenerated and in order to break this degeneracy, we added a perturbative term into the initial potential. We found new topological solutions for a specific Lagrangian that has a complex scalar field, studied by Trullinger and Subbaswamy in (Trullinger, S. E.; Subbaswamy, K. R. Physical Review A 19 (1979) 1340.), and applied the method of Poincar¶e section in this model checking its chaotic regions. / Mestre

Made available in DSpace on 2014-06-11T19:30:22Z (GMT). No. of bitstreams: 0 Previous issue date: 2010-02-10Bitstream added on 2014-06-13T20:40:18Z : No. of bitstreams: 1 santos_jrl_me_guara.pdf: 2847237 bytes, checksum: f5d09990f62bec6719d1ac0e52cd0fad (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Esta dissertacão tem como objetivo principal entender mais profundamente as mais variadas nuances do aparecimento de caos em sistemas de teoria de campos, além de um estudo sobre o comportamento das soluções solitônicas desses sistemas. Apresentamos um método, baseado na estrutura de m¶³nimos de potenciais, a ¯m de obter informações concretas sobre o comportamento das soluções solitônicas destes potenciais. Vericamos ainda a existência de novas soluções topologicas para um modelo que ¶e aplicado na descrição dos chamados twis- tons. Essas soluções possuem a particularidade de serem degeneradas, assim, para quebrar essa degenerescência, adicionamos ao potencial inicial um termo perturbativo. Determinamos também, novas soluções topologicas para uma lagrangiana contendo um campo escalar complexo, estudada por Trullinger e Subbaswamy em (Trullinger, S. E.; Subbaswamy, K. R. Physical Review A 19 (1979) 1340.) e por fim, aplicamos o método da seção de Poincare neste modelo verificando suas regioes caóticas. / The main objective of this work is a deeper comprehension about the different kinds of the appearing of chaos in field theory's systems, besides the study about the behavior of these soliton solutions systems. We present a method, based on the structure of potential's minima, to get information about the behavior of the solitons solutions. We calculate new topological solutions for a model that was applied to the description of the so called twistons. These solutions are degenerated and in order to break this degeneracy, we added a perturbative term into the initial potential. We found new topological solutions for a specific Lagrangian that has a complex scalar field, studied by Trullinger and Subbaswamy in (Trullinger, S. E.; Subbaswamy, K. R. Physical Review A 19 (1979) 1340.), and applied the method of Poincar¶e section in this model checking its chaotic regions.

Dissertação (mestrado)—Universidade de Brasília, Instituto de Ciências Exatas, Departamento de Matemática, Programa de Pós-Graduação em Matemática, 2014. / Submitted by Ana Cristina Barbosa da Silva (annabds@hotmail.com) on 2014-12-10T12:44:06Z No. of bitstreams: 1 2014_ValterBorgesSampaioJunior.pdf: 479129 bytes, checksum: 283e235f9ec7e5484f25ce686567f10e (MD5) / Approved for entry into archive by Patrícia Nunes da Silva(patricia@bce.unb.br) on 2014-12-15T14:35:47Z (GMT) No. of bitstreams: 1 2014_ValterBorgesSampaioJunior.pdf: 479129 bytes, checksum: 283e235f9ec7e5484f25ce686567f10e (MD5) / Made available in DSpace on 2014-12-15T14:35:47Z (GMT). No. of bitstreams: 1 2014_ValterBorgesSampaioJunior.pdf: 479129 bytes, checksum: 283e235f9ec7e5484f25ce686567f10e (MD5) / Nesta dissertação será apresentado um estudo de classes de métricas Riemannianas, tendo como objetivo um resultado de classificação de sólitons de Ricci gradiente, steady ou shrinking, que são localmente conformemente planos. Este resultado é baseado em um trabalho de Manuel Fernández Lopéz e Eduardo García Río, onde os autores mostram que todo sóliton de Ricci gradiente completo, localmente conformemente plano e simplesmente conexo deve ser localmente isométrico ao produto warped de uma forma espacial com uma variedade unidimensional. Se, em adição, tal sóliton for shrinking ou steady, então deve ser rotacionalmente simétrico. _________________________________________________________________________________ ABSTRACT / In this dissertation it will be presented a study about classes of Riemannian metrics, where the goal is a classification result of locally conformally at steady or shrinking gradient Ricci solitons. This result is based on an article due to Manuel Fernández Lopéz and Eduardo García Río, where it is proved that a locally conformally at gradient Ricci soliton, simply connected, is locally isometric to an warped product of a space form with an one dimensional manifold. In addition, if such soliton is shrinking or steady, then it will be rotationally symmetric.

No description available.

Quantum chaos has emerged in the half of the last century with the notorious problem of scattering of heavy nuclei. Since then, theoreticians have developed powerful techniques to approach disordered quantum systems. In the late 70's, Casati and Chirikov initiated a new field of research by studying the quantum counterpart of classical problems that are known to exhibit chaos. Among the several quantum-classical chaotic systems studied, the kicked rotor stimulated a lot of enthusiasm in the scientific community due to its equivalence to the Anderson tight binding model. This equivalence allows one to map the random Anderson model into a set of fully deterministic equations, making the theoretical analysis of Anderson localization considerably simpler. In the one-dimensional linear regime, it is known that Anderson localization always prevents the diffusion of the momentum. On the other hand, for higher dimensions it was demonstrated that for certain conditions of the disorder parameter, Anderson localized modes can be inhibited, allowing then a phase transition from localized (insulating) to delocalized (metallic) states. In this thesis we will numerically and theoretically investigate the properties of a multidimensional quantum kicked rotor in a nonlinear medium. The presence of nonlinearity is particularly interesting as it raises the possibility of having soliton waves as eigenfunctions of the systems. We keep the generality of our approach by using an adjustable diffusive nonlinearity, which can describe several physical phenomena. By means of Variational Calculus we develop a chaotic map which fully describes the soliton dynamics. The analysis of such a map shows a rich physical scenario that evidences the wave-particle behavior of a soliton. Through the nonlinearity, we trace a correspondence between quantum and classical mechanics, which has no equivalent in linearized systems. Matter waves experiments provide an ideal environment for studying Anderson localization, as the interactions in these systems can be easily controlled by Feshbach resonance techniques. In the end of this thesis, we propose an experimental realization of the kicked rotor in a dipolar Bose Einstein Condensate.

No description available.

Throughout the last several decades many techniques have been developed in establishing solutions to nonlinear partial differential equations (NPDE). These techniques are characterized by their limited reach in solving large classes of NPDE. This body of work will study the analysis of NPDE using two of the most ubiquitous techniques developed in the last century. In this body of work, the analysis and techniques herein are applied to unsolved physical problems in both the fields of variational approximations and inverse scattering transform. Additionally, a new technique for estimating the error of a variational approximation is established. Note that the material in chapter 2, "Quantitative Measurements of Variational Approximations" has recently been published. Variational problems have long been used to mathematically model physical systems. Their advantage has been the simplicity of the model as well as the ability to deduce information concerning the functional dependence of the system on various parameters embedded in the variational trial functions. However, the only method in use for estimating the error in a variational approximation has been to compare the variational result to the exact solution. In this work, it is demonstrated that one can computationally obtain estimates of the errors in a one-dimensional variational approximation, without any a priori knowledge of the exact solution. Additionally, this analysis can be done by using only linear techniques. The extension of this method to multidimensional problems is clearly possible, although one could expect that additional difficulties would arise. One condition for the existence of a localized soliton is that the propagation constant does not fall into the continuous spectrum of radiation modes. For a higher order dispersive systems, the linear dispersion relation exhibits a multiple branch structure. It could be the case that in a certain parameter region for which one of the components of the solution has oscillations (i.e., is in the continuous spectrum), there exists a discrete value of the propagation constant, k(ES), for which the oscillations have zero amplitude. The associated solution is referred to as an embedded soliton (ES). This work examines the ES solutions in a CHI(2):CHI(3), type II system. The method employed in searching for the ES solutions is a variational method recently developed by Kaup and Malomed [Phys. D 184, 153-61 (2003)] to locate ES solutions in a SHG system. The variational results are validated by numerical integration of the governing system. A model used for the 1-D longitudinal wave propagation in microstructured solids is a KdV-type equation with third and fifth order dispersions as well as first and third order nonlinearities. Recent work by Ilison and Salupere (2004) has identified certain types of soliton solutions in the aforementioned model. The present work expands the known family of soliton solutions in the model to include embedded solitons. The existence of embedded solitons with respect to the dispersion parameters is determined by a variational approximation. The variational results are validated with selected numerical solutions.

No description available.

Static, spherically-symmetric particle-like solutions to the coupled Einstein-Dirac and Einstein-Dirac-Maxwell equations have been studied by Finster, Smoller and Yau (FSY). In their work, FSY left the fermion mass as a parameter set to ±1. This thesis generalises these equations to include the Higgs field, letting the fermion mass become a function through coupling, μ. We discuss the dynamics associated with the Higgs field and find that there exist qualitatively similar solutions to those found by FSY, with well behaved, non-divergent metric components and electrostatic potential, close to the origin, going over to the point-particle solutions for large r; the Schwarzschild or Reissner-Nordström metric, and the Coulomb potential. We then go on to discuss an alternative gravity theory, conformal gravity, (CG), and look for solutions of the CG equations of motion coupled to the Dirac, Higgs and Maxwell equations. We obtain asymptotically nonvanishing, yet fully normalisable Dirac spinor components, resembling those of FSY, and, in the case where charge is included, non-divergent electrostatic potential close to the origin, matching onto the Coulomb potential for large r.

In this thesis, we attempt to obtain a class of generalized bilinear differential equations in (3+1)-dimensions by Dp-operators with p = 5, which have resonant solutions. We construct resonant solutions by using the linear superposition principle and parameterizations of wave numbers and frequencies. We test different values of p in Maple computations, and generate three classes of generalized bilinear differential equations and their resonant solutions when p = 5.