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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

Hamiltonsche Dynamik in einem räumlich ungeordneten eindimensionalen Kick-Potential

Hartwig, Ines 08 March 2009 (has links) (PDF)
Die vorliegende Arbeit kombiniert Aspekte der nichtlinearen Dynamik mit denen der Unordnungsphysik. Die bekannte Standardabbildung wird mit einem räumlich ungeordneten aber periodischen Potential modifiziert. Transportexponenten sowohl für den Impuls als auch die kanonisch konjugierte Koordinate für das Standard- und das Zufallsmodell werden gegenübergestellt. Für das Zufallspotential ergibt sich verstärkter Transport. Gemittelte Transportexponenten des Zufallspotentials werden präsentiert und für verschiedene Systemausdehnungen verglichen. / The thesis at hand combines aspects of nonlinear dynamics with the physics of disorder. The standard map potential is replaced by a spatially quenched random periodic potential. Transport exponents for the standard and the random model are determined for the momentum as well as the canonically conjugate coordinate. Transport for the disordered potential is increased in comparison to the standard map. For the random case, quenched average transport exponents are presented. Finite-size effects are examined.
2

Hamiltonsche Dynamik in einem räumlich ungeordneten eindimensionalen Kick-Potential

Hartwig, Ines 12 December 2007 (has links)
Die vorliegende Arbeit kombiniert Aspekte der nichtlinearen Dynamik mit denen der Unordnungsphysik. Die bekannte Standardabbildung wird mit einem räumlich ungeordneten aber periodischen Potential modifiziert. Transportexponenten sowohl für den Impuls als auch die kanonisch konjugierte Koordinate für das Standard- und das Zufallsmodell werden gegenübergestellt. Für das Zufallspotential ergibt sich verstärkter Transport. Gemittelte Transportexponenten des Zufallspotentials werden präsentiert und für verschiedene Systemausdehnungen verglichen. / The thesis at hand combines aspects of nonlinear dynamics with the physics of disorder. The standard map potential is replaced by a spatially quenched random periodic potential. Transport exponents for the standard and the random model are determined for the momentum as well as the canonically conjugate coordinate. Transport for the disordered potential is increased in comparison to the standard map. For the random case, quenched average transport exponents are presented. Finite-size effects are examined.
3

Stability in the plane planetary three-body problem / Stabilité dans le problème à trois corps planétaire plan

Castan, Thibaut 21 April 2017 (has links)
Arnold a démontré l'existence de solutions quasipériodiques dans le problème planétaire à trois corps plan, sous réserve que la masse de deux des corps, les planètes, soit petite par rapport à celle du troisième, le Soleil. Cette condition de petitesse dépend de façon cachée de la largeur d'analyticité de l'hamiltonien du problème, dans des coordonnées transcendantes. Hénon ex- plicita un rapport de masses minimal nécessaire à l'application du théorème de Arnold. L'objectif de cette thèse sera de donner une condition suffisante sur les rapports de masses. Une première partie de mon travail consiste à estimer cette largeur d'analyticité, ce qui passe par l'étude précise de l'équation de Kepler dans le complexe, ainsi que celle des singularités complexes de la fonction perturbatrice. Une deuxième partie consiste à mettre l'hamiltonien sous forme normale, dans l'optique d'une application du théorème KAM (du nom de Kolmogorov-Arnold-Moser). Il est nécessaire d'étudier le hamiltonien séculaire pour le mettre sous une forme normale adéquate. On peut alors quantifier la non-dégénérescence de l'hamiltonien séculaire, ainsi qu'estimer la perturbation. Enfin, il faut démontrer une version quantitative fine du théorème KAM, inspirée de Pöschel, avec des constantes explicites. A l'issue de ce travail, il est montré que le théorème KAM peut être appliqué pour des rapports de masses entre planètes et étoile de l'ordre de 10^(-85). / Arnold showed the existence of quasi-periodic solutions in the plane planetary three-body prob- lem, provided that the mass of two of the bodies, the planets, is small compared to the mass of the third one, the Sun. This smallness condition depends in a sensitive way on the analyticity widths of the Hamiltonian of the three-body problem, expressed with the help of some tran- scendental coordinates. Hénon gave a minimal ratio of masses necessary to the application of Arnold’s theorem. The main objective of this thesis is to determine a sufficient condition on this ratio. A first part of this work consists in estimating these analyticity widths, which requires a precise study of the complex Kepler equation, as well as the complex singularities of the disturb- ing function. A second part consists in reworking the Hamiltonian to put it under normal form, in order to apply the KAM theorem (KAM standing for Kolmogorov-Arnold-Moser). In this aim, it is essential to work with the secular Hamiltonian to put it under a suitable normal form. We can then quantify the non-degeneracy of the secular Hamiltonian, as well as estimate the perturbation. Finally, it is necessary to derive a quantitative version of the KAM theorem, in order to identify the hypotheses necessary for its application to the plane three-body problem. After this work, it is shown that the KAM theorem can be applied for a ratio of masses that is close to 10^(−85) between the planets and the star.
4

Integrabilidade e dinâmica global de sistema diferenciais polinomiais definidos em R³ com superfícies algébricas invariantes de graus 1 e 2 / Integrability and global dynamics of polynomial differential systems defined in R³ with invariant algebraic surfaces of degrees 1 and 2

Reinol, Alisson de Carvalho [UNESP] 05 July 2017 (has links)
Submitted by Alisson de Carvalho Reinol null (alissoncarv@gmail.com) on 2017-07-18T15:03:51Z No. of bitstreams: 1 tese_alisson_final.pdf: 6086108 bytes, checksum: 610534618b19a1d27cfff678d44f1a4a (MD5) / Approved for entry into archive by LUIZA DE MENEZES ROMANETTO (luizamenezes@reitoria.unesp.br) on 2017-07-19T14:22:46Z (GMT) No. of bitstreams: 1 reinol_ac_dr_sjrp.pdf: 6086108 bytes, checksum: 610534618b19a1d27cfff678d44f1a4a (MD5) / Made available in DSpace on 2017-07-19T14:22:46Z (GMT). No. of bitstreams: 1 reinol_ac_dr_sjrp.pdf: 6086108 bytes, checksum: 610534618b19a1d27cfff678d44f1a4a (MD5) Previous issue date: 2017-07-05 / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / Neste trabalho, consideramos aspectos algébricos e dinâmicos de alguns problemas envolvendo superfícies algébricas invariantes em sistemas diferenciais polinomiais definidos em R³. Determinamos o número máximo de planos invariantes que um sistema diferencial quadrático pode ter e estudamos a realização e integrabilidade de tais sistemas. Fornecemos a forma normal para sistemas diferenciais com quádricas invariantes e estudamos de forma mais detalhada a dinâmica e integrabilidade de sistemas diferenciais quadráticos com um paraboloide elíptico como superfície algébrica invariante. Por fim, estudamos as consequências dinâmicas ao se perturbar um sistema diferencial, cujo espaço de fase é folheado por superfícies algébricas invariantes. Para tal, consideramos o sistema diferencial quadrático conhecido como sistema Sprott A, que depende de um parâmetro real a e apresenta comportamento caótico mesmo sem ter pontos de equilíbrio, tendo, assim, um hidden attractor para valores adequados do parâmetro a. Provamos que, para a=0, o espaço de fase desse sistema é folheado por esferas concêntricas invariantes. Utilizando a Teoria do Averaging e o Teorema KAM (Kolmogorov-Arnold-Moser), provamos que, para a>0 suficientemente pequeno, uma órbita periódica orbitalmente estável emerge de um equilíbrio do tipo zero-Hopf não isolado localizado na origem e que formam-se toros invariantes em torno desta órbita periódica. Concluímos que a ocorrência de tais fatos tem um papel importante na formação do hidden attractor. / In this work, we consider algebraic and dynamical aspects of some problems involving invariant algebraic surfaces in polynomial differential systems defined in R³. We determine the maximum number of invariant planes that a quadratic differential system can have and we study the realization and integrability of such systems. We provide the normal form for differential systems having an invariant quadric and we study in more detail the dynamics and integrability of quadratic differential systems having an elliptic paraboloid as invariant algebraic surface. Finally, we study the dynamic consequences of perturbing differential system whose phase space is foliated by invariant algebraic surfaces. For this we consider the quadratic differential system known as Sprott A system, which depends on one real parameter a and presents chaotic behavior even without having any equilibrium point, thus having a hidden attractor for suitable values of parameter a. We prove that, for a=0, the phase space of this system is foliated by invariant concentric spheres. By using the Averaging Theory and the KAM (Kolmogorov-Arnold-Moser) Theorem, we prove that, for a>0 sufficiently small, an orbitally stable periodic orbit emerges from a zero-Hopf nonisolated equilibrium point located at the origin and that invariant tori are formed around this periodic orbit. We conclude that the occurrence of these facts has an important role in the formation of the hidden attractor. / FAPESP: 2013/26602-7

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