MEAN CURVATURE FLOW in HIGHER CODIMENSION By
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DISCRETE DIFFERENTIAL GEOMETRY: an APPLIED INTRODUCTION Keenan Crane • CMU 15-458/858 LECTURE 15: CURVATURE
DISCRETE DIFFERENTIAL GEOMETRY: AN APPLIED INTRODUCTION Keenan Crane • CMU 15-458/858 LECTURE 15: CURVATURE DISCRETE DIFFERENTIAL GEOMETRY: AN APPLIED INTRODUCTION Keenan Crane • CMU 15-458/858 Curvature—Overview • Intuitively, describes “how much a shape bends” – Extrinsic: how quickly does the tangent plane/normal change? – Intrinsic: how much do quantities differ from flat case? N T B Curvature—Overview • Driving force behind wide variety of physical phenomena – Objects want to reduce—or restore—their curvature – Even space and time are driven by curvature… Curvature—Overview • Gives a coordinate-invariant description of shape – fundamental theorems of plane curves, space curves, surfaces, … • Amazing fact: curvature gives you information about global topology! – “local-global theorems”: turning number, Gauss-Bonnet, … Curvature—Overview • Geometric algorithms: shape analysis, local descriptors, smoothing, … • Numerical simulation: elastic rods/shells, surface tension, … • Image processing algorithms: denoising, feature/contour detection, … Thürey et al 2010 Gaser et al Kass et al 1987 Grinspun et al 2003 Curvature of Curves Review: Curvature of a Plane Curve • Informally, curvature describes “how much a curve bends” • More formally, the curvature of an arc-length parameterized plane curve can be expressed as the rate of change in the tangent Equivalently: Here the angle brackets denote the usual dot product, i.e., . Review: Curvature and Torsion of a Space Curve •For a plane curve, curvature captured the notion of “bending” •For a space curve we also have torsion, which captures “twisting” Intuition: torsion is “out of plane bending” increasing torsion Review: Fundamental Theorem of Space Curves •The fundamental theorem of space curves tells that given the curvature κ and torsion τ of an arc-length parameterized space curve, we can recover the curve (up to rigid motion) •Formally: integrate the Frenet-Serret equations; intuitively: start drawing a curve, bend & twist at prescribed rate. -
Curvatures of Smooth and Discrete Surfaces
Curvatures of Smooth and Discrete Surfaces John M. Sullivan The curvatures of a smooth curve or surface are local measures of its shape. Here we consider analogous quantities for discrete curves and surfaces, meaning polygonal curves and triangulated polyhedral surfaces. We find that the most useful analogs are those which preserve integral relations for curvature, like the Gauß/Bonnet theorem. For simplicity, we usually restrict our attention to curves and surfaces in euclidean three space E3, although many of the results would easily generalize to other ambient manifolds of arbitrary dimension. Most of the material here is not new; some is even quite old. Although some refer- ences are given, no attempt has been made to give a comprehensive bibliography or an accurate picture of the history of the ideas. 1. Smooth curves, Framings and Integral Curvature Relations A companion article [Sul06] investigated the class of FTC (finite total curvature) curves, which includes both smooth and polygonal curves, as a way of unifying the treatment of curvature. Here we briefly review the theory of smooth curves from the point of view we will later adopt for surfaces. The curvatures of a smooth curve γ (which we usually assume is parametrized by its arclength s) are the local properties of its shape invariant under Euclidean motions. The only first-order information is the tangent line; since all lines in space are equivalent, there are no first-order invariants. Second-order information is given by the osculating circle, and the invariant is its curvature κ = 1/r. For a plane curve given as a graph y = f(x) let us contrast the notions of curvature and second derivative. -
Differential Geometry: Curvature and Holonomy Austin Christian
University of Texas at Tyler Scholar Works at UT Tyler Math Theses Math Spring 5-5-2015 Differential Geometry: Curvature and Holonomy Austin Christian Follow this and additional works at: https://scholarworks.uttyler.edu/math_grad Part of the Mathematics Commons Recommended Citation Christian, Austin, "Differential Geometry: Curvature and Holonomy" (2015). Math Theses. Paper 5. http://hdl.handle.net/10950/266 This Thesis is brought to you for free and open access by the Math at Scholar Works at UT Tyler. It has been accepted for inclusion in Math Theses by an authorized administrator of Scholar Works at UT Tyler. For more information, please contact [email protected]. DIFFERENTIAL GEOMETRY: CURVATURE AND HOLONOMY by AUSTIN CHRISTIAN A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science Department of Mathematics David Milan, Ph.D., Committee Chair College of Arts and Sciences The University of Texas at Tyler May 2015 c Copyright by Austin Christian 2015 All rights reserved Acknowledgments There are a number of people that have contributed to this project, whether or not they were aware of their contribution. For taking me on as a student and learning differential geometry with me, I am deeply indebted to my advisor, David Milan. Without himself being a geometer, he has helped me to develop an invaluable intuition for the field, and the freedom he has afforded me to study things that I find interesting has given me ample room to grow. For introducing me to differential geometry in the first place, I owe a great deal of thanks to my undergraduate advisor, Robert Huff; our many fruitful conversations, mathematical and otherwise, con- tinue to affect my approach to mathematics. -
Rapport Annuel 2014-2015
RAPPORT ANNUEL 2014-2015 Présentation du rapport annuel 1 Programme thématique 2 Autres activités 12 Grandes Conférences et colloques 16 Les laboratoires du CRM 20 Les prix du CRM 30 Le CRM et la formation 34 Les partenariats du CRM 38 Les publications du CRM 40 Comités à la tête du CRM 41 Le CRM en chiffres 42 Luc Vinet Présentation En 2014-2015, contrairement à ce qui était le cas dans (en physique mathématique) à Charles Gale de l’Université les années récentes, le programme thématique du CRM a McGill et le prix CRM-SSC (en statistique) à Matías été consacré à un seul thème (très vaste !) : la théorie des Salibián-Barrera de l’Université de Colombie-Britannique. nombres. L’année thématique, intitulée « La théorie des Les Grandes conférences du CRM permirent au grand public nombres : de la statistique Arithmétique aux éléments Zêta », de s’initier à des sujets variés, présentés par des mathémati- a été organisée par les membres du CICMA, un laboratoire ciens chevronnés : Euler et les jets d’eau de Sans-Souci du CRM à la fine pointe de la recherche mondiale, auxquels il (par Yann Brenier), la mesure des émotions en temps réel faut ajouter Louigi Addario-Berry (du Groupe de probabilités (par Chris Danforth), le mécanisme d’Anticythère (par de Montréal). Je tiens à remercier les quatre organisateurs de James Evans) et l’optique et les solitons (par John Dudley). cette brillante année thématique : Henri Darmon de l’Univer- L’année 2014-2015 fut également importante du point de sité McGill, Chantal David de l’Université Concordia, Andrew vue de l’organisation et du financement du CRM. -
Simulation of a Soap Film Catenoid
View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by Kanazawa University Repository for Academic Resources Simulation of A Soap Film Catenoid ! ! Pornchanit! Subvilaia,b aGraduate School of Natural Science and Technology, Kanazawa University, Kakuma, Kanazawa 920-1192 Japan bDepartment of Mathematics, Faculty of Science, Chulalongkorn University, Pathumwan, Bangkok 10330 Thailand E-mail: [email protected] ! ! ! Abstract. There are many interesting phenomena concerning soap film. One of them is the soap film catenoid. The catenoid is the equilibrium shape of the soap film that is stretched between two circular rings. When the two rings move farther apart, the radius of the neck of the soap film will decrease until it reaches zero and the soap film is split. In our simulation, we show the evolution of the soap film when the rings move apart before the !film splits. We use the BMO algorithm for the evolution of a surface accelerated by the mean curvature. !Keywords: soap film catenoid, minimal surface, hyperbolic mean curvature flow, BMO algorithm !1. Introduction The phenomena that concern soap bubble and soap films are very interesting. For example when soap bubbles are blown with any shape of bubble blowers, the soap bubbles will be round to be a minimal surface that is the minimized surface area. One of them that we are interested in is a soap film catenoid. The catenoid is the minimal surface and the equilibrium shape of the soap film stretched between two circular rings. In the observation of the behaviour of the soap bubble catenoid [3], if two rings move farther apart, the radius of the neck of the soap film will decrease until it reaches zero. -
Department of Mathematics
Department of Mathematics The Department of Mathematics seeks to maintain its top ranking in mathematics research and education in the United States. The department is a key part of MIT’s educational mission at both the undergraduate and graduate levels and produces the most sought-after young researchers. Key to the department’s success is recruitment of the best faculty members, postdoctoral associates, and graduate students in an ever more competitive environment. The department strives to be diverse at all levels in terms of race, gender, and ethnicity. It continues to serve the varied needs of its graduate students, undergraduate students majoring in mathematics, and the broader MIT community. Awards and Honors The faculty received numerous distinctions this year. Professor Victor Kac received the Leroy P. Steele Prize for Lifetime Achievement, for “groundbreaking contributions to Lie Theory and its applications to Mathematics and Mathematical Physics.” Larry Guth (together with Netz Katz of the California Institute of Technology) won the Clay Mathematics Institute Research Award. Tomasz Mrowka was elected as a member of the National Academy of Sciences and William Minicozzi was elected as a fellow of the American Academy of Arts and Sciences. Alexei Borodin received the 2015 Loève Prize in Probability, given by the University of California, Berkeley, in recognition of outstanding research in mathematical probability by a young researcher. Alan Edelman received the 2015 Babbage Award, given at the IEEE International Parallel and Distributed Processing Symposium, for exceptional contributions to the field of parallel processing. Bonnie Berger was elected vice president of the International Society for Computational Biology. -
Mean Curvature in Manifolds with Ricci Curvature Bounded from Below
Comment. Math. Helv. 93 (2018), 55–69 Commentarii Mathematici Helvetici DOI 10.4171/CMH/429 © Swiss Mathematical Society Mean curvature in manifolds with Ricci curvature bounded from below Jaigyoung Choe and Ailana Fraser Abstract. Let M be a compact Riemannian manifold of nonnegative Ricci curvature and † a compact embedded 2-sided minimal hypersurface in M . It is proved that there is a dichotomy: If † does not separate M then † is totally geodesic and M † is isometric to the Riemannian n product † .a; b/, and if † separates M then the map i 1.†/ 1.M / induced by W ! inclusion is surjective. This surjectivity is also proved for a compact 2-sided hypersurface with mean curvature H .n 1/pk in a manifold of Ricci curvature RicM .n 1/k, k > 0, and for a free boundary minimal hypersurface in an n-dimensional manifold of nonnegative Ricci curvature with nonempty strictly convex boundary. As an application it is shown that a compact .n 1/-dimensional manifold N with the number of generators of 1.N / < n 1 n cannot be minimally embedded in the flat torus T . Mathematics Subject Classification (2010). 53C20, 53C42. Keywords. Ricci curvature, minimal surface, fundamental group. 1. Introduction Euclid’s fifth postulate implies that there exist two nonintersecting lines on a plane. But the same is not true on a sphere, a non-Euclidean plane. Hadamard [11] generalized this to prove that every geodesic must meet every closed geodesic on a surface of positive curvature. Note that a k-dimensional minimal submanifold of a Riemannian manifold M is a critical point of the k-dimensional area functional. -
Department of Mathematics, Report to the President 2015-2016
Department of Mathematics The Department of Mathematics continues to be the top-ranked mathematics department in the United States. The department is a key part of MIT’s educational mission at both the undergraduate and graduate levels and produces top sought- after young researchers. Key to the department’s success is recruitment of the very best faculty, postdoctoral fellows, and graduate students in an ever-more competitive environment. The department aims to be diverse at all levels in terms of race, gender, and ethnicity. It continues to serve the varied needs of the department’s graduate students, mathematics majors, and the broader MIT community. Awards and Honors The faculty received numerous distinctions this year. Professor Emeritus Michael Artin was awarded the National Medal of Science. In 2016, President Barack Obama presented this honor to Artin for his outstanding contributions to mathematics. Two other emeritus professors also received distinctions: Professor Bertram Kostant was selected to receive the 2016 Wigner Medal, in recognition of “outstanding contributions to the understanding of physics through Group Theory.” Professor Alar Toomre was elected member of the American Philosophical Society. Among active faculty, Professor Larry Guth was awarded the New Horizons in Mathematics Prize for “ingenious and surprising solutions to long standing open problems in symplectic geometry, Riemannian geometry, harmonic analysis, and combinatorial geometry.” He also received a 2015 Teaching Prize for Graduate Education from the School of Science. Professor Alexei Borodin received the 2015 Henri Poincaré Prize, awarded every three years at the International Mathematical Physics Congress to recognize outstanding contributions in mathematical physics. He also received a 2016 Simons Fellowship in Mathematics. -
Arxiv:1805.06667V4 [Math.NA] 26 Jun 2019 Kowloon, Hong Kong E-Mail: [email protected] 2 B
Version of June 27, 2019 A convergent evolving finite element algorithm for mean curvature flow of closed surfaces Bal´azsKov´acs · Buyang Li · Christian Lubich This paper is dedicated to Gerhard Dziuk on the occasion of his 70th birthday and to Gerhard Huisken on the occasion of his 60th birthday. Abstract A proof of convergence is given for semi- and full discretizations of mean curvature flow of closed two-dimensional surfaces. The numerical method proposed and studied here combines evolving finite elements, whose nodes determine the discrete surface like in Dziuk's method, and linearly implicit backward difference formulae for time integration. The proposed method dif- fers from Dziuk's approach in that it discretizes Huisken's evolution equations for the normal vector and mean curvature and uses these evolving geometric quantities in the velocity law projected to the finite element space. This nu- merical method admits a convergence analysis in the case of finite elements of polynomial degree at least two and backward difference formulae of orders two to five. The error analysis combines stability estimates and consistency esti- mates to yield optimal-order H1-norm error bounds for the computed surface position, velocity, normal vector and mean curvature. The stability analysis is based on the matrix{vector formulation of the finite element method and does not use geometric arguments. The geometry enters only into the consistency estimates. Numerical experiments illustrate and complement the theoretical results. Keywords mean curvature flow · geometric evolution equations · evolving surface finite elements · linearly implicit backward difference formula · stability · convergence analysis Mathematics Subject Classification (2000) 35R01 · 65M60 · 65M15 · 65M12 B. -
Basics of the Differential Geometry of Surfaces
Chapter 20 Basics of the Differential Geometry of Surfaces 20.1 Introduction The purpose of this chapter is to introduce the reader to some elementary concepts of the differential geometry of surfaces. Our goal is rather modest: We simply want to introduce the concepts needed to understand the notion of Gaussian curvature, mean curvature, principal curvatures, and geodesic lines. Almost all of the material presented in this chapter is based on lectures given by Eugenio Calabi in an upper undergraduate differential geometry course offered in the fall of 1994. Most of the topics covered in this course have been included, except a presentation of the global Gauss–Bonnet–Hopf theorem, some material on special coordinate systems, and Hilbert’s theorem on surfaces of constant negative curvature. What is a surface? A precise answer cannot really be given without introducing the concept of a manifold. An informal answer is to say that a surface is a set of points in R3 such that for every point p on the surface there is a small (perhaps very small) neighborhood U of p that is continuously deformable into a little flat open disk. Thus, a surface should really have some topology. Also,locally,unlessthe point p is “singular,” the surface looks like a plane. Properties of surfaces can be classified into local properties and global prop- erties.Intheolderliterature,thestudyoflocalpropertieswascalled geometry in the small,andthestudyofglobalpropertieswascalledgeometry in the large.Lo- cal properties are the properties that hold in a small neighborhood of a point on a surface. Curvature is a local property. Local properties canbestudiedmoreconve- niently by assuming that the surface is parametrized locally. -
Hamilton's Ricci Flow
The University of Melbourne, Department of Mathematics and Statistics Hamilton's Ricci Flow Nick Sheridan Supervisor: Associate Professor Craig Hodgson Second Reader: Professor Hyam Rubinstein Honours Thesis, November 2006. Abstract The aim of this project is to introduce the basics of Hamilton's Ricci Flow. The Ricci flow is a pde for evolving the metric tensor in a Riemannian manifold to make it \rounder", in the hope that one may draw topological conclusions from the existence of such \round" metrics. Indeed, the Ricci flow has recently been used to prove two very deep theorems in topology, namely the Geometrization and Poincar´eConjectures. We begin with a brief survey of the differential geometry that is needed in the Ricci flow, then proceed to introduce its basic properties and the basic techniques used to understand it, for example, proving existence and uniqueness and bounds on derivatives of curvature under the Ricci flow using the maximum principle. We use these results to prove the \original" Ricci flow theorem { the 1982 theorem of Richard Hamilton that closed 3-manifolds which admit metrics of strictly positive Ricci curvature are diffeomorphic to quotients of the round 3-sphere by finite groups of isometries acting freely. We conclude with a qualitative discussion of the ideas behind the proof of the Geometrization Conjecture using the Ricci flow. Most of the project is based on the book by Chow and Knopf [6], the notes by Peter Topping [28] (which have recently been made into a book, see [29]), the papers of Richard Hamilton (in particular [9]) and the lecture course on Geometric Evolution Equations presented by Ben Andrews at the 2006 ICE-EM Graduate School held at the University of Queensland. -
Analysis & PDE Vol. 5 (2012)
ANALYSIS & PDE Volume 5 No. 1 2012 mathematical sciences publishers Analysis & PDE msp.berkeley.edu/apde EDITORS EDITOR-IN-CHIEF Maciej Zworski University of California Berkeley, USA BOARD OF EDITORS Michael Aizenman Princeton University, USA Nicolas Burq Université Paris-Sud 11, France [email protected] [email protected] Luis A. Caffarelli University of Texas, USA Sun-Yung Alice Chang Princeton University, USA [email protected] [email protected] Michael Christ University of California, Berkeley, USA Charles Fefferman Princeton University, USA [email protected] [email protected] Ursula Hamenstaedt Universität Bonn, Germany Nigel Higson Pennsylvania State Univesity, USA [email protected] [email protected] Vaughan Jones University of California, Berkeley, USA Herbert Koch Universität Bonn, Germany [email protected] [email protected] Izabella Laba University of British Columbia, Canada Gilles Lebeau Université de Nice Sophia Antipolis, France [email protected] [email protected] László Lempert Purdue University, USA Richard B. Melrose Massachussets Institute of Technology, USA [email protected] [email protected] Frank Merle Université de Cergy-Pontoise, France William Minicozzi II Johns Hopkins University, USA [email protected] [email protected] Werner Müller Universität Bonn, Germany Yuval Peres University of California, Berkeley, USA [email protected] [email protected] Gilles Pisier Texas A&M University, and Paris 6 Tristan Rivière ETH, Switzerland [email protected] [email protected] Igor Rodnianski Princeton University, USA Wilhelm Schlag University of Chicago, USA [email protected] [email protected] Sylvia Serfaty New York University, USA Yum-Tong Siu Harvard University, USA [email protected] [email protected] Terence Tao University of California, Los Angeles, USA Michael E.