by Ho Wing Kin. / Thesis submitted in: July 1997. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1998. / Includes bibliographical references (leaves 89-92). / Chapter 1 --- Introduction --- p.5 / Chapter 1.1 --- The Euler-Lagrange Equation for Capillary Surfaces --- p.6 / Chapter 1.2 --- The Capillary Tube --- p.12 / Chapter 2 --- Comparison Principles --- p.16 / Chapter 2.1 --- The General Comparison Principle --- p.16 / Chapter 2.2 --- Applications --- p.24 / Chapter 3 --- Existence Criteria --- p.30 / Chapter 3.1 --- Necessary Conditions --- p.31 / Chapter 3.2 --- Sufficient Conditions --- p.35 / Chapter 4 --- Uniqueness --- p.53 / Chapter 4.1 --- General Bounded Domains Case --- p.53 / Chapter 4.2 --- Infinite Strip Case --- p.56 / Chapter 5 --- Gradient Estimate of Surfaces of Constant Mean Curvature --- p.66 / Chapter 5.1 --- The Gradient Estimate --- p.67 / Chapter 5.2 --- Behavior as R→ 1 --- p.70 / Chapter 5.3 --- Existence of the Comparison Surfaces --- p.76 / Chapter 5.4 --- Ro is Best Possible --- p.82 / Appendix Mean Curvature --- p.85

Thesis (Ph.D.)--University of Delaware, 2008. / Principal faculty advisor: John A. Pelesko, Dept. of Mathematical Sciences. Includes bibliographical references.

A teoria das transforma»ções de superfícies de curvatura constante começou, no fim do século XIX, com o trabalho [3] de A.V. Bäcklund e, em seguida, recebeu importantes contribuições por parte de diversos geômetras, entre eles, L. Bianchi e C. Guichard (veja, por exemplo, [5, 6, 7, 17]). Nessa dissertação apresentamos alguns dos mais importantes resultados desse tópico da geometria diferencial que estão relacionados às superfícies de curvatura média (ou gaussiana não nula) constante. Tais superfícies estão associadas a soluções de equações diferenciais parciais de segunda ordem e não lineares. A interpretação analítica da teoria das transformações de superfícies de curvatura constante nos capacita obter soluções dessas equações diferenciais parciais a partir de uma outra dada, mediante integração de um sistema de equações diferenciais, chamado transformação de Bäcklund. Então, os teoremas de permutabilidade fornecem uma \"fórmula de superposição\" para a construção algébrica de novas soluções / The theory on transformations of surfaces with constant curvature begins, in the late nineteen century, with the article [3] of A.V. Bäcklund and, after, received important contributions from various geometricians, among others, L. Bianchi and C. Guichard (see, for example, [5, 6, 7, 17]). In this dissertation we outline some of the most important results on the theory of surfaces of constant mean (or gaussian) curvature. Such surfaces are associated to the solutions of nonlinear partial differential equations of second order. The analytic interpretation of the theory on transformations of constant curvature surfaces provides a method of obtaining, from a given solution of these partial differential equations, a new solution of the same equation, by integrating a system of differential equations, called Bäcklund transformation. Then, the permutability theorems give a \"superposition formula\" to construct, algebraically, new solutions

The n-point Steiner problem in the Euclidean plane is to find a least length path network connecting n points. In this thesis we will demonstrate how to find a least length path network T connecting n points on a closed 2-dimensional Riemannian surface of constant curvature by determining a region in the covering space that is guaranteed to contain T. We will then provide an algorithm for solving the n-point Steiner problem on such a surface.

Made available in DSpace on 2015-04-22T22:16:13Z (GMT). No. of bitstreams: 1 Ana Acacia Pereira Valente.pdf: 221896 bytes, checksum: f7a5ffc2646f76d06002549f557bd363 (MD5) Previous issue date: 2003-12-19 / The work of this essay is to make a clear on detailed exposition of the two theorems of the article of Lúcio Rodriguez and Renato Tribuzy on the Reduction of Codimension of Regular Immersions in the space of constant curvature c. We show that if M is a compact and connected manifold, of dimension n, and is an immersion (formula) regular, that is, when the first normal space N generated by image of the second fundamental form has constant dimension 1, then we can reduce the codimension of the immersion to 1. Other result important in the work show that if M is complete, connected with non-negative Ricci curvature, then f is a cylinder over a curve our we can reduce the codimension to 1 and f(M) is the boundary of a convex set in an a±ne subspace of (formula). / Este trabalho tem como finalidade apresentar uma exposição clara e detalhada de dois dos teoremas apresentados no artigo de Lúcio Rodriguez e Renato Tribuzy sobre Redução de Codimensão de Imersões Regulares em Espaços de Curvatura Constante c. Mostra-se que se tivermos uma variedade compacta e conexa M, de dimensão n, e uma imersão (formula) regular, isto é, quando a dimensão do primeiro espaço normal N gerado pelas imagens da segunda forma fundamental tem dimensão constante igual a 1, então podemos reduzir a codimensão da imersão para 1. Outro resultado importante neste trabalho é o fato de que se a variedade é apenas completa, conexa e com curvatura de Ricci não-negativa, então a imersão será um cilindro sobre uma curva, do contrário, podemos reduzir a codimensão para 1 e nossa imersão será o bordo de um corpo convexo em um subespaço (formula).

Abstract not available

Abstract not available

FundaÃÃo Cearense de Apoio ao Desenvolvimento Cientifico e TecnolÃgico / Nesta tese, estudamos hipersuperfÃcies de tipo-espaÃo completas imersas em variedades semi-Riemannianas, satisfazendo alguma condiÃÃo sobre suas curvaturas de ordem superior, a fim de obtermos resultados tipo-Bernstein. As ferramentas analÃticas que utilizamos sÃo algumas versÃes do princÃpio do mÃximo. No caso em que o ambiente à um espaÃo-tempo de Robertson-Walker generalizado satisfazendo a condiÃÃo forte de convergÃncia nula, obtemos novas caracterizaÃÃes de hipersuperfÃcies tipo-espaÃo totalmente geodÃsicas. AlÃm disso, obtemos uma estimativa inferior do Ãndice mÃnimo de nulidade relativa quando a hipersuperfÃcie tipo-espaÃo à r-mÃxima ou quando existem duas curvaturas mÃdias de ordem superior consecutivas que nÃo mudam de sinal. TambÃm obtemos resultados de rigidez e novas caracterizaÃÃes de hipersuperfÃcies totalmente umbÃlicas, supondo que estas possuem alguma curvatura de ordem superior constante e que o ambiente à um espaÃo-tempo de Robertson-Walker satisfazendo a condiÃÃo de convergÃncia nula. Aplicamos tais resultados aos espaÃo de de Sitter e anti-de Sitter. Finalmente, provamos um teorema tipo-Bernstein para hipersuperfÃcies completas, com curvatura mÃdia constante, imersas em um produto riemanniano. / In this thesis, we study complete space-like hypersurfaces immersed in semi-Riemannian manifolds, satisfying some conditions on their higher-order mean curvatures in order to get Bernstein-type results. Analytical tools we use are some versions of the maximum principle. When the ambient space is a generalized Robertson-Walker spacetime which is supposed to obey the strong null convergence condition, we establish new characterizations of totally geodesic spacelike hypersurfaces. Furthermore, we obtain a lower estimate the minimum index of relative nullity when the space-like hypersurface is r-maximal, or when there are two consecutive higher-order mean curvatures that do not change sin. We also obtain rigidity results and new characterizations of totally umbilical hypersurfaces, assuming they have some constant higher-order mean curvature, and that the ambient space is a spacetime Robertson-Walker obeying the null convergence condition. These results are applied to the de Sitter and anti-de Sitter spaces. Finally, we prove a Bernstein-type theorem for constant mean curvature complete hypersurfaces immersed in a riemannian product.

Orientador: Alberto Vazquez Saa / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Matemática, Estatística e Computação Científica / Made available in DSpace on 2018-08-20T03:54:09Z (GMT). No. of bitstreams: 1 Leal_Isabel_M.pdf: 984828 bytes, checksum: b0a33558ae8b5683163892248364a85b (MD5) Previous issue date: 2012 / Resumo: Nesta dissertação, fazemos uma revisão da literatura existente sobre vórtices em superfícies de curvatura constante, dando especial atenção às questões de integrabilidade e não integrabilidade. Além disso, apresentamos alguns resultados originais sobre o movimento de vórtices no plano hiperbólico que indicam um possível caminho para demonstrar a não integrabilidade de um sistema de quatro vórtices nessa superfície / Abstract: In this thesis, we review the existing literature on vortices on surfaces of constant curvature, giving special attention to the issues of integrability and non-integrability. In addition, we present some original results on the motion of vortices on the hyperbolic plane that indicate a possible way to demonstrate the non-integrability of a system of four vortices on that surface / Mestrado / Matematica / Mestre em Matemática

A second-order Lagrangian system is a generalization of a classical mechanical system for which the Lagrangian action depends on the second derivative of the state variable. Recent work has shown that the dynamics of such systems c:an be substantially richer than for classical Lagrangian systems. In particular, topological properties of the planar curves obtained by projection onto the lower-order derivatives play a key role in forcing certain types of dynamics. However, the application of these techniques requires an analytic restriction on the Lagrangian that it satisfy a twist property. In this dissertation we approach this problem from the point of view of curve shortening in an effort to remove the twist condition. In classical curve shortening a family of curves evolves with a velocity which is normal to the curve and proportional to its curvature. The evolution of curves with decreasing action is more general, and in the first part of this dissertation we develop some results for curve shortening flows which shorten lengths with respect to a Finsler metric rather than a Riemannian metric. The second part of this dissertation focuses on analytic methods to accommodate the fact that the Finsler metric for second-order Lagrangian system has singularities. We prove the existence of simple periodic solutions for a general class of systems without requiring the twist condition. Further; our results provide a frame work in which to try to further extend the topological forcing theorems to systems without the twist condition. / Includes bibliography. / Dissertation (Ph.D.)--Florida Atlantic University, 2014. / FAU Electronic Theses and Dissertations Collection