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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

Geometry of jet bundles and the structure of Lagrangian and Hamiltonian formalisms

Kupershmidt, Boris A.,1946- January 1979 (has links)
Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Mathematics, 1979. / Bibliography: leaves 58-59. / by Boris A. Kupershmidt. / Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Mathematics, 1979.
2

Métodos de volumes finitos centrados unsplitting utilizados na obtenção de soluções em magnetohidrodinâmica relativística : aplicações em discos e jatos / Centered finite volume methods unsplitting used in the obtaining of solutions in relativistic magnetohydrodynamics : applications in disks and jets

Garcia, Raphael de Oliveira, 1982- 24 August 2018 (has links)
Orientador: Samuel Rocha de Oliveira / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Matemática Estatística e Computação Científica / Made available in DSpace on 2018-08-24T16:31:57Z (GMT). No. of bitstreams: 1 Garcia_RaphaeldeOliveira_D.pdf: 5512062 bytes, checksum: a2805b263757b93de5fb67b8cc3aba15 (MD5) Previous issue date: 2013 / Resumo: Neste trabalho foi desenvolvido um novo programa computacional em Fortran 90, com o objetivo de obter soluções numéricas de um sistema de equações diferenciais parciais de Magnetohidrodinâmica Relativística, com gravitação pré-determinada (GRMHD), capaz de simular a formação de jatos relativísticos desde a acreção de disco de matéria até sua ejeção. De início fez-se um estudo sobre métodos numéricos de Volumes Finitos Unidimensionais, a saber método Lax-Friedrichs, Lax-Wendroff, Nessyahu-Tadmor e métodos de Godunov dependentes de problemas de Riemann, aplicados nas equações de Euler com o intuito de verificar as suas principais características e de efetuar comparações entre aqueles métodos. Em seguida implementou-se os métodos de Volumes Finitos Centrados Lax-Friedrichs e Nessyahu-Tadmor, que são esquemas numéricos que possuem uma formulação sem separação dimensional e livres de resolvedores de problemas de Riemann, mesmo em duas ou mais dimensões espaciais; neste ponto, já aplicados nas equações de GRMHD. Um método Lax-Wendroff com Runge-Kutta de ordem 3, com a propriedade de ser Valor Total Decrescente (TVD) no tempo e com separação dimensional, também foi aplicado no mesmo problema. Por fim, com o método Nessyahu-Tadmor foi possível obter soluções numéricas estáveis - sem oscilações espúrias nem dissipação excessiva - desde o processo de acreção do disco magnetizado, em rotação com relação a um buraco negro central (BH) de Schwarzschild e imerso a uma magnetosfera, até a ejeção de matéria em forma de jato ao longo de uma distância de quatorze vezes o raio do BH, um recorde em termos de simulação astrofísica / Abstract: We have developed a new computer program in Fortran 90, in order to obtain numerical solutions of a system of partial differential equations of Relativistic Magnetohydrodynamics with predetermined gravitation (GRMHD), capable of simulate the formation of relativistic jets from the accretion disk of matter up to his ejection. Initially we carried out a study on numerical methods of Unidimensional Finite Volume, namely Lax-Friedrichs, Lax-Wendroff, Nessyahu-Tadmor method and Godunov methods dependent on Riemann problems, applied to equations Euler in order to verify their main features and make comparisons among those methods. It was then implemented the methods of Finite Volume Centered Lax-Friedrichs and Nessyahu-Tadmor, which are numerical schemes that have a formulation free and without dimensional separation Riemann problem solvers, even in two or more spatial dimensions, at this point, already applied in equations GRMHD. A Lax-Wendrof Runge-Kutta method of order 3, with the property of Total Value Descending (TVD) in time and size separation, was also applied to the same problem. Finally, with Nessyahu - Tadmor method was possible to obtain solutions stable numerical - without spurious oscillations or excessive dissipation - from the process of magnetized accretion disk, in rotation with respect to a central black hole (BH) Schwarzschild and immersed in a magnetosphere, to the ejection of matter in the form of jet over a distance of fourteen times the radius of the BH, a record in terms of astrophysical simulation / Doutorado / Matematica / Doutor em Matemática Aplicada
3

Soluções invariantes de operadores diferenciais definidos em fibrados / Invariant solutions of differential operations defined in bundles

França, Elizeu Cleber dos Santos, 1987- 25 August 2018 (has links)
Orientador: Pedro José Catuogno / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Matemática Estatística e Computação Científica / Made available in DSpace on 2018-08-25T09:06:57Z (GMT). No. of bitstreams: 1 Franca_ElizeuCleberdosSantos_M.pdf: 3490670 bytes, checksum: 6589d1bb5b880e51625fb93abb2964a9 (MD5) Previous issue date: 2014 / Resumo: Neste trabalho, apresentaremos a teoria básica de simetrias de equações diferenciais, focando na busca por soluções invariantes de operadores diferenciais definidos em fibrados vetoriais com relação a ação transversal de um grupo de Lie no fibrado em questão / Abstract: In this work we will give the basic theory of symmetries of differential equations. The goal of this work is searching for invariant solutions of differential operators which are defined on vector bundles with respect to the transverse action of a Lie group in such bundle / Mestrado / Matematica / Mestre em Matemática
4

Infinitely Divisible Metrics, Curvature Inequalities And Curvature Formulae

Keshari, Dinesh Kumar 07 1900 (has links) (PDF)
The curvature of a contraction T in the Cowen-Douglas class is bounded above by the curvature of the backward shift operator. However, in general, an operator satisfying the curvature inequality need not be contractive. In this thesis, we characterize a slightly smaller class of contractions using a stronger form of the curvature inequality. Along the way, we find conditions on the metric of the holomorphic Hermitian vector bundle E corresponding to the operator T in the Cowen-Douglas class which ensures negative definiteness of the curvature function. We obtain a generalization for commuting tuples of operators in the Cowen-Douglas class. Secondly, we obtain an explicit formula for the curvature of the jet bundle of the Hermitian holomorphic bundle E f on a planar domain Ω. Here Ef is assumed to be a pull-back of the tautological bundle on gr(n, H ) by a nondegenerate holomorphic map f :Ω →Gr (n, H ). Clearly, finding relationships amongs the complex geometric invariants inherent in the short exact sequence 0 → Jk(Ef ) → Jk+1(Ef ) →J k+1(Ef )/ Jk(Ef ) → 0 is an important problem, whereJk(Ef ) represents the k-th order jet bundle. It is known that the Chern classes of these bundles must satisfy c(Jk+1(Ef )) = c(Jk(Ef )) c(Jk+1(Ef )/ Jk(Ef )). We obtain a refinement of this formula: trace Idnxn ( KJk(Ef )) - trace Idnxn ( KJk-1(Ef ))= KJk(Ef )/ Jk-1(Ef )(z).

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