Introduction to Topological Manifolds (Second Edition)
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07. Homeomorphisms and Embeddings
07. Homeomorphisms and embeddings Homeomorphisms are the isomorphisms in the category of topological spaces and continuous functions. Definition. 1) A function f :(X; τ) ! (Y; σ) is called a homeomorphism between (X; τ) and (Y; σ) if f is bijective, continuous and the inverse function f −1 :(Y; σ) ! (X; τ) is continuous. 2) (X; τ) is called homeomorphic to (Y; σ) if there is a homeomorphism f : X ! Y . Remarks. 1) Being homeomorphic is apparently an equivalence relation on the class of all topological spaces. 2) It is a fundamental task in General Topology to decide whether two spaces are homeomorphic or not. 3) Homeomorphic spaces (X; τ) and (Y; σ) cannot be distinguished with respect to their topological structure because a homeomorphism f : X ! Y not only is a bijection between the elements of X and Y but also yields a bijection between the topologies via O 7! f(O). Hence a property whose definition relies only on set theoretic notions and the concept of an open set holds if and only if it holds in each homeomorphic space. Such properties are called topological properties. For example, ”first countable" is a topological property, whereas the notion of a bounded subset in R is not a topological property. R ! − t Example. The function f : ( 1; 1) with f(t) = 1+jtj is a −1 x homeomorphism, the inverse function is f (x) = 1−|xj . 1 − ! b−a a+b The function g :( 1; 1) (a; b) with g(x) = 2 x + 2 is a homeo- morphism. Therefore all open intervals in R are homeomorphic to each other and homeomorphic to R . -
Counterexamples in Topology
Counterexamples in Topology Lynn Arthur Steen Professor of Mathematics, Saint Olaf College and J. Arthur Seebach, Jr. Professor of Mathematics, Saint Olaf College DOVER PUBLICATIONS, INC. New York Contents Part I BASIC DEFINITIONS 1. General Introduction 3 Limit Points 5 Closures and Interiors 6 Countability Properties 7 Functions 7 Filters 9 2. Separation Axioms 11 Regular and Normal Spaces 12 Completely Hausdorff Spaces 13 Completely Regular Spaces 13 Functions, Products, and Subspaces 14 Additional Separation Properties 16 3. Compactness 18 Global Compactness Properties 18 Localized Compactness Properties 20 Countability Axioms and Separability 21 Paracompactness 22 Compactness Properties and Ts Axioms 24 Invariance Properties 26 4. Connectedness 28 Functions and Products 31 Disconnectedness 31 Biconnectedness and Continua 33 VII viii Contents 5. Metric Spaces 34 Complete Metric Spaces 36 Metrizability 37 Uniformities 37 Metric Uniformities 38 Part II COUNTEREXAMPLES 1. Finite Discrete Topology 41 2. Countable Discrete Topology 41 3. Uncountable Discrete Topology 41 4. Indiscrete Topology 42 5. Partition Topology 43 6. Odd-Even Topology 43 7. Deleted Integer Topology 43 8. Finite Particular Point Topology 44 9. Countable Particular Point Topology 44 10. Uncountable Particular Point Topology 44 11. Sierpinski Space 44 12. Closed Extension Topology 44 13. Finite Excluded Point Topology 47 14. Countable Excluded Point Topology 47 15. Uncountable Excluded Point Topology 47 16. Open Extension Topology 47 17. Either-Or Topology 48 18. Finite Complement Topology on a Countable Space 49 19. Finite Complement Topology on an Uncountable Space 49 20. Countable Complement Topology 50 21. Double Pointed Countable Complement Topology 50 22. Compact Complement Topology 51 23. -
General Topology
General Topology Tom Leinster 2014{15 Contents A Topological spaces2 A1 Review of metric spaces.......................2 A2 The definition of topological space.................8 A3 Metrics versus topologies....................... 13 A4 Continuous maps........................... 17 A5 When are two spaces homeomorphic?................ 22 A6 Topological properties........................ 26 A7 Bases................................. 28 A8 Closure and interior......................... 31 A9 Subspaces (new spaces from old, 1)................. 35 A10 Products (new spaces from old, 2)................. 39 A11 Quotients (new spaces from old, 3)................. 43 A12 Review of ChapterA......................... 48 B Compactness 51 B1 The definition of compactness.................... 51 B2 Closed bounded intervals are compact............... 55 B3 Compactness and subspaces..................... 56 B4 Compactness and products..................... 58 B5 The compact subsets of Rn ..................... 59 B6 Compactness and quotients (and images)............. 61 B7 Compact metric spaces........................ 64 C Connectedness 68 C1 The definition of connectedness................... 68 C2 Connected subsets of the real line.................. 72 C3 Path-connectedness.......................... 76 C4 Connected-components and path-components........... 80 1 Chapter A Topological spaces A1 Review of metric spaces For the lecture of Thursday, 18 September 2014 Almost everything in this section should have been covered in Honours Analysis, with the possible exception of some of the examples. For that reason, this lecture is longer than usual. Definition A1.1 Let X be a set. A metric on X is a function d: X × X ! [0; 1) with the following three properties: • d(x; y) = 0 () x = y, for x; y 2 X; • d(x; y) + d(y; z) ≥ d(x; z) for all x; y; z 2 X (triangle inequality); • d(x; y) = d(y; x) for all x; y 2 X (symmetry). -
Spacetime Singularities Vs. Topologies in the Zeeman-Göbel
Spacetime Singularities vs. Topologies in the Zeeman-Gobel¨ Class Kyriakos Papadopoulos1, Basil K. Papadopoulos2 1. Department of Mathematics, Kuwait University, PO Box 5969, Safat 13060, Kuwait 2. Department of Civil Engineering, Democritus University of Thrace, Greece Abstract In this article we first observe that the Path topology of Hawking, King and Mac- Carthy is an analogue, in curved spacetimes, of a topology that was suggested by Zeeman as an alternative topology to his so-called Fine topology in Minkowski space- time. We then review a result of a recent paper on spaces of paths and the Path topology, and see that there are at least five more topologies in the class Z − G of Zeeman-G¨obel topologies which admit a countable basis, incorporate the causal and conformal structures, but the Limit Curve Theorem fails to hold. The ”problem” that arXiv:1712.03270v6 [math-ph] 18 Jun 2018 L.C.T. does not hold can be resolved by ”adding back” the light-cones in the basic-open sets of these topologies, and create new basic open sets for new topologies. But, the main question is: do we really need the L.C.T. to hold, and why? Why is the manifold topology, under which the group of homeomorphisms of a spacetime is vast and of no physical significance (Zeeman), more preferable from an appropriate topology in the class Z − G under which a homeomorphism is an isometry (G¨obel)? Since topological conditions that come as a result of a causality requirement are key in the existence of singularities in general relativity, the global topological conditions that one will supply the spacetime manifold might play an important role in describing the transition from the quantum non-local theory to a classical local theory. -
Topological Properties
CHAPTER 4 Topological properties 1. Connectedness • Definitions and examples • Basic properties • Connected components • Connected versus path connected, again 2. Compactness • Definition and first examples • Topological properties of compact spaces • Compactness of products, and compactness in Rn • Compactness and continuous functions • Embeddings of compact manifolds • Sequential compactness • More about the metric case 3. Local compactness and the one-point compactification • Local compactness • The one-point compactification 4. More exercises 63 64 4. TOPOLOGICAL PROPERTIES 1. Connectedness 1.1. Definitions and examples. Definition 4.1. We say that a topological space (X, T ) is connected if X cannot be written as the union of two disjoint non-empty opens U, V ⊂ X. We say that a topological space (X, T ) is path connected if for any x, y ∈ X, there exists a path γ connecting x and y, i.e. a continuous map γ : [0, 1] → X such that γ(0) = x, γ(1) = y. Given (X, T ), we say that a subset A ⊂ X is connected (or path connected) if A, together with the induced topology, is connected (path connected). As we shall soon see, path connectedness implies connectedness. This is good news since, unlike connectedness, path connectedness can be checked more directly (see the examples below). Example 4.2. (1) X = {0, 1} with the discrete topology is not connected. Indeed, U = {0}, V = {1} are disjoint non-empty opens (in X) whose union is X. (2) Similarly, X = [0, 1) ∪ [2, 3] is not connected (take U = [0, 1), V = [2, 3]). More generally, if X ⊂ R is connected, then X must be an interval. -
16. Compactness
16. Compactness 1 Motivation While metrizability is the analyst's favourite topological property, compactness is surely the topologist's favourite topological property. Metric spaces have many nice properties, like being first countable, very separative, and so on, but compact spaces facilitate easy proofs. They allow you to do all the proofs you wished you could do, but never could. The definition of compactness, which we will see shortly, is quite innocuous looking. What compactness does for us is allow us to turn infinite collections of open sets into finite collections of open sets that do essentially the same thing. Compact spaces can be very large, as we will see in the next section, but in a strong sense every compact space acts like a finite space. This behaviour allows us to do a lot of hands-on, constructive proofs in compact spaces. For example, we can often take maxima and minima where in a non-compact space we would have to take suprema and infima. We will be able to intersect \all the open sets" in certain situations and end up with an open set, because finitely many open sets capture all the information in the whole collection. We will specifically prove an important result from analysis called the Heine-Borel theorem n that characterizes the compact subsets of R . This result is so fundamental to early analysis courses that it is often given as the definition of compactness in that context. 2 Basic definitions and examples Compactness is defined in terms of open covers, which we have talked about before in the context of bases but which we formally define here. -
Connected Fundamental Groups and Homotopy Contacts in Fibered Topological (C, R) Space
S S symmetry Article Connected Fundamental Groups and Homotopy Contacts in Fibered Topological (C, R) Space Susmit Bagchi Department of Aerospace and Software Engineering (Informatics), Gyeongsang National University, Jinju 660701, Korea; [email protected] Abstract: The algebraic as well as geometric topological constructions of manifold embeddings and homotopy offer interesting insights about spaces and symmetry. This paper proposes the construction of 2-quasinormed variants of locally dense p-normed 2-spheres within a non-uniformly scalable quasinormed topological (C, R) space. The fibered space is dense and the 2-spheres are equivalent to the category of 3-dimensional manifolds or three-manifolds with simply connected boundary surfaces. However, the disjoint and proper embeddings of covering three-manifolds within the convex subspaces generates separations of p-normed 2-spheres. The 2-quasinormed variants of p-normed 2-spheres are compact and path-connected varieties within the dense space. The path-connection is further extended by introducing the concept of bi-connectedness, preserving Urysohn separation of closed subspaces. The local fundamental groups are constructed from the discrete variety of path-homotopies, which are interior to the respective 2-spheres. The simple connected boundaries of p-normed 2-spheres generate finite and countable sets of homotopy contacts of the fundamental groups. Interestingly, a compact fibre can prepare a homotopy loop in the fundamental group within the fibered topological (C, R) space. It is shown that the holomorphic condition is a requirement in the topological (C, R) space to preserve a convex path-component. Citation: Bagchi, S. Connected However, the topological projections of p-normed 2-spheres on the disjoint holomorphic complex Fundamental Groups and Homotopy subspaces retain the path-connection property irrespective of the projective points on real subspace. -
Topology of Energy Surfaces and Existence of Transversal Poincaré Sections
Topology of energy surfaces and existence of transversal Poincar´esections Alexey Bolsinova Holger R. Dullinb Andreas Wittekb a) Department of Mechanics and Mathematics Moscow State University Moscow 119899, Russia b) Institut f¨ur Theoretische Physik Universit¨at Bremen Postfach 330440 28344 Bremen, Germany Email: [email protected] February 1996 Abstract Two questions on the topology of compact energy surfaces of natural two degrees of freedom Hamiltonian systems in a magnetic field are discussed. We show that the topology of this 3-manifold (if it is not a unit tangent bundle) is uniquely determined by the Euler characteristic of the accessible region in arXiv:chao-dyn/9602023v1 29 Feb 1996 configuration space. In this class of 3-manifolds for most cases there does not exist a transverse and complete Poincar´esection. We show that there are topological obstacles for its existence such that only in the cases of S1 × S2 and T 3 such a Poincar´esection can exist. 1 Introduction The question of the topology of the energy surface of Hamiltonian systems was al- ready treated in the 20’s by Birkhoff and Hotelling [8, 9]. Birkhoff proposed the “streamline analogy” [3], i.e. the idea that the flow of a Hamiltonian system on the 3-manifold could be viewed as the streamlines of an incompressible fluid evolving in this manifold. Extending the work of Poincar´e[14] he noted that it might be difficult 1 to find a transverse Poincar´esection which is complete (i.e. for which every stream- line starting from the surface of section returns to it) [1]. -
Finite Topological Spaces with Maple
University of Benghazi Faculty of Science Department of Mathematics Finite Topological Spaces with Maple A dissertation Submitted to the Department of Mathematics in Partial Fulfillment of the requirements for the degree of Master of Science in Mathematics By Taha Guma el turki Supervisor Prof. Kahtan H.Alzubaidy Benghazi –Libya 2013/2014 Dedication For the sake of science and progress in my country new Libya . Taha ii Acknowledgements I don’t find words articulate enough to express my gratitude for the help and grace that Allah almighty has bestowed upon me. I would like to express my greatest thanks and full gratitude to my supervisor Prof. Kahtan H. Al zubaidy for his invaluable assistance patient guidance and constant encouragement during the preparation of the thesis. Also, I would like to thank the department of Mathematics for all their efforts advice and every piece of knowledge they offered me to achieve the accomplishment of writing this thesis. Finally , I express my appreciation and thanks to my family for the constant support. iii Contents Abstract ……………………………………………………….…1 Introduction ……………………………..……………………….2 Chapter Zero: Preliminaries Partially Ordered Sets …………………………………………….4 Topological Spaces ………………………………………………11 Sets in Spaces …………………………………………………... 15 Separation Axioms …...…………………………………………..18 Continuous Functions and Homeomorphisms .….......………………..22 Compactness …………………………………………………….24 Connectivity and Path Connectivity …..……………………………25 Quotient Spaces ……………………..…………………………...29 Chapter One: Finite Topological Spaces -
Review of Set Theory
Appendix A: Review of Set Theory In this book, as in most modern mathematics, mathematical statements are couched in the language of set theory. We give here a brief descriptive summary of the parts of set theory that we use, in the form that is commonly called “naive set theory.” The word naive should be understood in the same sense in which it is used by Paul Halmos in his classic text Naive Set Theory [Hal74]: the assumptions of set theory are to be viewed much as Euclid viewed his geometric axioms, as intuitively clear statements of fact from which reliable conclusions can be drawn. Our description of set theory is based on the axioms of Zermelo–Fraenkel set theory together with the axiom of choice (commonly known as ZFC), augmented with a notion of classes (aggregations that are too large to be considered sets in ZFC), primarily for use in category theory. We do not give a formal axiomatic treat- ment of the theory; instead, we simply give the definitions and list the basic types of sets whose existence is guaranteed by the axioms. For more details on the subject, consult any good book on set theory, such as [Dev93,Hal74,Mon69,Sup72,Sto79]. We leave it to the set theorists to explore the deep consequences of the axioms and the relationships among different axiom systems. Basic Concepts A set is just a collection of objects, considered as a whole. The objects that make up the set are called its elements or its members. For our purposes, the elements of sets are always “mathematical objects”: integers, real numbers, complex numbers, and objects built up from them such as ordered pairs, ordered n-tuples, functions, sequences, other sets, and so on. -
Counterexamples in Topology
Lynn Arthur Steen J. Arthur Seebach, Jr. Counterexamples in Topology Second Edition Springer-Verlag New York Heidelberg Berlin Lynn Arthur Steen J. Arthur Seebach, Jr. Saint Olaf College Saint Olaf College Northfield, Minn. 55057 Northfield, Minn. 55057 USA USA AMS Subject Classification: 54·01 Library of Congress Cataloging in Publication Data Steen, Lynn A 1941· Counterexamples in topology. Bibliography: p. Includes index. 1. Topological spaces. I. Seebach, J. Arthur, joint author. II. Title QA611.3.S74 1978 514'.3 78·1623 All rights reserved. No part of this book may be translated or reproduced in any form without written permission from Springer.Verlag Copyright © 1970, 1978 by Springer·Verlag New York Inc. The first edition was published in 1970 by Holt, Rinehart, and Winston Inc. 9 8 7 6 5 4 321 ISBN-13: 978-0-387-90312-5 e-ISBN-13:978-1-4612-6290-9 DOl: 1007/978-1-4612-6290-9 Preface The creative process of mathematics, both historically and individually, may be described as a counterpoint between theorems and examples. Al though it would be hazardous to claim that the creation of significant examples is less demanding than the development of theory, we have dis covered that focusing on examples is a particularly expeditious means of involving undergraduate mathematics students in actual research. Not only are examples more concrete than theorems-and thus more accessible-but they cut across individual theories and make it both appropriate and neces sary for the student to explore the entire literature in journals as well as texts. Indeed, much of the content of this book was first outlined by under graduate research teams working with the authors at Saint Olaf College during the summers of 1967 and 1968. -
Systems-Based Approaches at the Frontiers of Chemical Engineering and Computational Biology: Advances and Challenges
Systems-Based Approaches at the Frontiers of Chemical Engineering and Computational Biology: Advances and Challenges Christodoulos A. Floudas Princeton University Department of Chemical Engineering Program of Applied and Computational Mathematics Department of Operations Research and Financial Engineering Center for Quantitative Biology Outline • Theme: Scientific/Personal Journey • Research Philosophy at CASL (Computer Aided Systems Laboratory, Princeton University) • Research Areas: Advances & Challenges • Acknowledgements Greece Ioannina, Greece Ioannina,Greece (Courtesy of G. Floudas) Thessaloniki, Greece Aristotle University of Thessaloniki Department of Chemical Engineering Aristotle University of Thessaloniki Undergraduate Studies(1977-1982) Pittsburgh, PA Carnegie Mellon University Graduate Studies How did it all start? • Ph.D. Thesis: Sept. 82 – Dec. 85 •Advisor: Ignacio E. Grossmann • Synthesis of Flexible Heat Exchanger Networks (82-85) • Uncertainty Analysis (82-85) Princeton, NJ Princeton University Computer Aided Systems Laboratory Interface Product & Process Systems Engineering • Chemical Engineering • Applied Mathematics Research • Operations Research Areas • Computer Science • Computational Chemistry Computational Biology & Genomics • Computational Biology Unified Theory • address fundamental problems and applications via mathematical and Research modeling of microscopic, mesoscopic and macroscopic level Philosophy • rigorous optimization theory and algorithms • large scale computations in high performance clusters Mathematical