Gaussbonnet theorem simple english wikipedia, the free. This is an informal survey of some of the most fertile ideas which grew out of the attempts to better understand the meaning of this remarkable theorem. Let s be a closed orientable surface in r 3 with gaussian curvature k and euler characteristic. It is named after carl friedrich gauss, who was aware of a version of the theorem but never published it, and pierre ossian bonnet, who published a. Of course identifying this alternating sum with the alternating sum of the betti numbers of m, the so called morse equality, of necessity does require homological arguments. Aug 12, 2016 for a finitely triangulated closed surface m 2, let.
Here d is the exterior derivative, and d is its formal adjoint under the riemannian metric. On combinatorial gaussbonnet theorem for general euclidean. T does not depend on the triangulation but only on the surface and may therefore be denoted by. The integrand in the integral over r is a special function associated with a vector. Definitely it is the combinatorial counterpart to gaussbonnet theorem in differential geometry. The gaussbonnet theorem, like few others in geometry, is the source of many fundamental discoveries which are now part of the everyday language of the modern geometer. Rn is a closed surface if sis bounded, connected and closed as a set. Curvatura gaussiana wikipedia, a enciclopedia livre. Teorema di gauss il flusso del campo elettrico attraverso una.
In this singular limit the gaussbonnet invariant gives rise to nontrivial contributions to gravitational dynamics, while preserving the number of graviton degrees of freedom and being free from ostrogradsky instability. Chenchang zhu, the gaussbonnet theorem and its applications. This theorem relates curvature geometry to euler characteristic topology. Here s1p is the arc length of the unit sphere of p and s2p is the arc length of the. Gaussbonnet theorem an overview sciencedirect topics. Polyhedral gaussbonnet theorems and valuations rolf schneider abstract the gaussbonnet theorem for a polyhedron a union of nitely many compact convex polytopes in ndimensional euclidean space expresses the euler characteristic of the polyhedron as a sum of certain curvatures, which are di erent from zero only at the vertices of the polyhedron. Gaussbonnet for discrete surfaces sohini upadhyay abstract. It arises as the special case where the topological index is defined in terms of betti numbers and the analytical index is defined in terms of the gaussbonnet integrand as with the twodimensional gaussbonnet theorem, there are generalizations when m is a manifold with boundary.
A fantastic introduction that explains the gaussbonnet theorem in intuitive terms is geometry and topology in manyparticle systems by. In this paper i introduce and examine properties of discrete surfaces in e ort to prove a discrete gaussbonnet analog. The gaussbonnet theorem, or gaussbonnet formula, is an important statement about. Gauss theorem 3 this result is precisely what is called gauss theorem in r2. Le dimostrazioni relative a questa sezione vengono rinviate al testo di riferimento 1. Nov 26, 2017 for the love of physics walter lewin may 16, 2011 duration. Sejam rx,y,zx,y,z e fx,y,zq rx,y,z krx,y,zk3, onde qe constante. A region bounded by a simple closed curved with three vertices and three edges is called a triangle.
Since it is a topdimensional differential form, it is closed. Ichiro satake, the gaussbonnet theorem for vmanifolds j. Integrals add up whats inside them, so this integral represents the total amount of curvature of the manifold. About gaussbonnet theorem mathematics stack exchange. See robert greenes notes here, or the wikipedia page on gaussbonnet, or perhaps john lees riemannian manifolds book. Pdf a discrete gaussbonnet type theorem semantic scholar. The curvature of the shape is used, as well as its euler characteristic. The naturality of the euler class means that when changing the riemannian metric, one stays in the same cohomology class.
In short, it is a 2manifold with or without boundary which is equipped with a riemannian. Rather, it is an intrinsic statement about abstract riemannian 2manifolds. It is known that gaussbonnet contribution tends to weaken the singularity 16, 17 in the corresponding solution for n 5, 6. By the wellknown combinatorial version of the 2 dimensional gaussbonnet theorem, it holds. The gaussbonnetchern theorem on riemannian manifolds. Explanations in this section should contain no formulas, but instead colloquial things like you would hear them during a coffee break or at a cocktail party. Wendy stefan a rodr guez argueta ra3 y erick ulises velasquez orellana vo1 docentes asesores. In this talk we will start with the concept of combinatorial curvature on planar graphs. Thus, a surface of genus 2 is never periodic, and a minimal surface of genus g in a 3torus t 3 has 4 g. The study of this theorem has a long history dating back to gausss theorema egregium latin.
Come vedremo, il teorema di gauss bonnet ha una versione locale e una versione globale. The pusieux curvature kp 2s1p s2p is equal to 12 times the euler characteristic when summed over the boundary of g. We prove a prototype curvature theorem for subgraphs g of the flat triangular tesselation which play the analogue of domains in two dimensional euclidean space. The theorem tells us that there is a remarkable invariance on. A topological gaussbonnet theorem 387 this alternating sum to be. Gaussbonnet is a deep result in di erential geometry that illustrates a fundamental relationship between the curvature of a surface and its euler characteristic. Liviu nicolaescu, the many faces of the gaussbonnet theorem. The gaussbonnet theorem can be seen as a special instance in the theory of characteristic classes.
The gaussbonnet theorem implies that if m g is a minimal surface of genus g in a 3tours t 3, then its gauss map g. These notions of curvature tell us roughly what a surface looks like both locally and globally. The right hand side is some constant times the euler characteristic. Teorema di gauss per il campo elettrostatico premessa. Maria belen celis, jose abel semitiel y natalia fatima sgreccia. Gianmarco molino sigma seminar the gaussbonnet theorem 1 februrary, 2019 1623. We are finally in a position to prove our first major localglobal theorem in riemannian geometry. Hopfs generalization hopfl, hopf2 of the gaussbonnet theorem for hypersurfaces in.
The gaussbonnet theorem is also valid for a manifold with a piecewisesmooth boundary. It is named after carl friedrich gauss, who was aware of a version of the theorem but never published it, and pierre ossian bonnet, who published a special. Nella sua forma locale, il teorema di gaussbonnet per una qualunque sottosuperficie r di m e espresso dalla. After brief explanation for some progress related to combinatorial curvature, the main topic of this talk will come in, the combinatorial gaussbonnet theorem. Il teorema di gauss, al contrario della legge di coulomb, e di facile sperimentazione e misurazione. This is a localglobal theorem par excellence, because it asserts the equality of two very differently defined quantities on a compact, orientable riemannian 2manifold m. This publication is a propaedeutic monograph about gaussbonnet theorems. The left hand side is the integral of the gaussian curvature over the manifold. In this chapter we shall prove the generalized gaussbonnet theorem using tubes. The gaussbonnetchern theorem on riemannian manifolds yin li abstract this expository paper contains a detailed introduction to some important works concerning the gaussbonnetchern theorem. It is well known and was essentially proved by euler for the case of surfaces homeomorphic to s2 that. Part xxi the gaussbonnet theorem the goal for this part is to state and prove a version of the gaussbonnet theorem, also known as descartes angle defect formula. The gaussbonnet theorem is a theorem that connects the geometry of a shape with its topology. Combinatorial gaussbonnet theorem and its applications.
The simplest one expresses the total gaussian curvature of an embedded triangle in terms of the total geodesic curvature of the boundary and the jump angles at the corners more specifically, if is any 2d riemannian manifold like a surface in 3space and if is an embedded triangle, then the gaussbonnet. The gaussbonnet theorem, or gaussbonnet formula, is an important statement about surfaces in differential geometry, connecting their geometry in the sense of curvature to their topology in the sense of the euler characteristic. The lecture notes i am using however does not have the integral with the geodesic curvature but they seem to have the same hypotheses. The gaussbonnet theorem says that, for a closed 7 manifold. The total gaussian curvature of a closed surface depends only on the topology of the surface and is equal to 2. The gauss bonnet theorem, or gauss bonnet formula, is an important statement about surfaces in differential geometry, connecting their geometry in the sense of curvature to their topology in the sense of the euler characteristic. The gaussbonnet theorem is a special case when m is a 2d manifold. Gaussbonnet theorem and applications repositorio institucional.
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