Topology Definition and 816 Threads

In mathematics, topology (from the Greek words τόπος, 'place, location', and λόγος, 'study') is concerned with the properties of a geometric object that are preserved under continuous deformations, such as stretching, twisting, crumpling, and bending; that is, without closing holes, opening holes, tearing, gluing, or passing through itself.
A topological space is a set endowed with a structure, called a topology, which allows defining continuous deformation of subspaces, and, more generally, all kinds of continuity. Euclidean spaces, and, more generally, metric spaces are examples of a topological space, as any distance or metric defines a topology. The deformations that are considered in topology are homeomorphisms and homotopies. A property that is invariant under such deformations is a topological property. Basic examples of topological properties are: the dimension, which allows distinguishing between a line and a surface; compactness, which allows distinguishing between a line and a circle; connectedness, which allows distinguishing a circle from two non-intersecting circles.
The ideas underlying topology go back to Gottfried Leibniz, who in the 17th century envisioned the geometria situs and analysis situs. Leonhard Euler's Seven Bridges of Königsberg problem and polyhedron formula are arguably the field's first theorems. The term topology was introduced by Johann Benedict Listing in the 19th century, although it was not until the first decades of the 20th century that the idea of a topological space was developed.

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  1. J

    What Are Some Current Topics in Physics That Interest John Salkeld?

    The title above give my name. I am a pure maths PhD with an interest in physics and geometry. I am currently studying physics for fun and I am very interested in current progress. I am especially interested in quantisation of space time, holographic theories and dualities. Regards John
  2. L

    Signature, boundary conditions and topology

    It is said that the metric tensor in GR is generally covariant and obey diffeomorphism invariance.. but the signature, boundary conditions and topology are not. What would be GR like if these 3 obey GC and DI too? Is it possible?
  3. A

    How to prove a set belongs to Borel sigma-algebra?

    I am working on this problem on measure theory like this: Suppose ##X## is the set of real numbers, ##\mathcal B## is the Borel ##\sigma##-algebra, and ##m## and ##n## are two measures on ##(X, \mathcal B)## such that ##m((a, b))=n((a, b))< \infty## whenever ##−\infty<a<b<\infty##. Prove that...
  4. R

    How difficult is Topology for a pure Physics student?

    Hi, I'm hoping someone here can shed some light, I'm currently in my 3rd year of my Physics degree and have discovered I really don't have the mind to memorise / reproduce paragraphs of text. Even if I understand the concepts it takes me a LONG time for my brain to take text in. Maths however I...
  5. Z

    Fourier Analysis vs Topology: Which is More Useful for Physics?

    Hey guys, long story short. I am completing my Math minor this semester and need to decide on whether Topology or Fourier Analysis. I am an undergraduate physics major and neither one of those classes is required for my B.S. in physics. So what do you guys think, Topology or Fourier Analysis?
  6. M

    Topology of Black Holes: Possible Topologies & Examples

    This might be well known or even discussed here, though I couldn't find a thread about it, but the questions is what are the possible topologies of a black hole i.e. the topology of a spatial slice of the event horizon. I know there is a result of Hawking that says the topology has to be that of...
  7. C

    Easy question regarding the basis for a topology

    Hello, I know that given a set $X$ and a topology $T$ on $X$ that a basis $B$ for $T$ is a collection of open sets of $T$ such that every open set of $T$ is the Union of sets in $B$. My question is: does taking the set of all Unions of sets in $B$ give exactly the topology $T$ ?
  8. X

    Math REU with focus on topology/analysis

    I have been looking through the AMS and NSF websites for REUs. And I have found some in particular that I am interested in(UChicago, Cornell, SMALL, MAPS-REU), but it seems these are the only ones that have projects that deal with topology/analysis. Do any of you have any suggestions for REUs...
  9. M

    Topology required for topological quantum computing?

    I guess the usual answer would be to learn as much as possible. Some background about me: I am not a physicist but I'd like to pursue a PhD in theoretical physics (after a year or two) and work on topological quantum computing. I am familiar with quantum mechanics and solid state physics (at...
  10. K

    What are the topological properties of the FLRW model?

    So, I was trying to do a derivation of my own for the FLRW metric, since I couldn't understand the one Wald had. The spatial slice M is a connected Riemannian manifold which is everywhere isotropic. That is, in every point p\in M and unit vectors in v_1,v_2\in T_p\left(M\right) there is an...
  11. V

    Allowed values for the "differentiability limit" in complex analysis

    In complex analysis differentiability for a function ##f## at a point ##z_0## in the interior of the domain of ##f## is defined as the existence of the limit $$ \lim_{h\rightarrow{}0}\frac{f(z_0+h)-f(z_0)}{h}.$$ But why are the possible ##z_0##'s in the closure of the domain of the original...
  12. H

    Convergence Criteria for Box Topology on R^ω

    Hi, What are the convergent sequences in the box topology on R^ω?Are they the eventually constant only? Thank's in advance
  13. V

    Topology of Relativity: Implications of Niels Bohr's Arguments

    I have seen in the online Stanford Encyclopedia of Philosophy in the entry on Copenhagen Interpretation of Quantum Mechanics that Niels Bohr had argued that the theory of relativity is not a literal representation of the universe: "Neither does the theory of relativity, Bohr argued, provide us...
  14. C

    Finding the absolute minimum of a function in R2

    Homework Statement Use technique of completing squares to Show that this function has an absolute minimum. f(x, y) = x^2 + y^2 − 2x + 4y + 1 Homework Equations Not entirely sure how completing the squares will indicate an absolute minimum.Is there some additional reasoning required? The...
  15. S

    Question on testing logical truths for set operations

    My question is on how to answer if two statements are equal in set theory. Like De'Morgans laws for example. I'm currently reading James Munkres' book "Topology" and am working through the set theory chapters now, and this isn't the first time I've seen the material, but every time I see this...
  16. T

    Topology or logic or other start point?

    So i just recently had to drop two math courses, topology, math logic, because my math maturity wasn't up to the level needed to excel in them. I intend on taking them again, but not without first more preparation which leads to my question. Which order would i benefit more from in preparing for...
  17. JonnyMaddox

    What is the Geometric Interpretation of Principal Bundles with Lie Group Fibres?

    I'm trying to learn how to think about principal bundles where the fibre is a lie group with local trivialization ϕ^{-1}_i:π(U_i)→U_i×G . For example ϕ^{-1}_i:π(S^2)→S^2×U(1) (if that makes sense) . But I don't know how to think of this (and other products with lie groups like that)...
  18. camilus

    The Grassmanian manifold's topology

    Let n <= m and G:=Gr(n,m) be the (real) Grassmanian manifold. I understand the topology of the simplest case, that of projective space, and am wondering if there is a way to interpret the topology of the G to similar to projective space, with the according generalizations needed. If V^n is an...
  19. T

    Showing that a given function is continous over a certain topology

    Consider the maps h: R^w (omega) ---> R^w (omega) , h (x1, x2, x3,...) = (x1,4x2, 9x3,...) g: (same dimension mapping) , g (t) = (t, t, t, t, t,...) Is h continuous whn given the product topology, box topology, uniform topology? For the life of me i am...
  20. Chacabucogod

    Exploring the Topology of the Cuk Converter

    Hi, I'm currently studying the topology of the cuk converter and I'm wondering why do you hhave to add that first inductor to the topology? Can't you just charge the capacitor straight through the voltage source? Thank you.
  21. shounakbhatta

    Which branch of topology to study

    Hello, I learned that there are 4 types of approach to topology: (1) General (2) Algebraic (3) Differential (4) Geometrical To have a rough understanding of General relativity, which branch of topology should I study? Thanks.
  22. T

    Proving B(r,x) is a Subset of S^c: Basic Topology Question

    Assume ##|X| > \rho## , let ##r = |X| - \rho## Now I am trying to show that ##B(r,x)\subseteq S^c## This should be a simple question, but I am struggling trying to find the right inequlity. Attempt: let ##y## be a point in ##B(r,x)##. I know that ##|x - y| < r##. I have to somehow show...
  23. M

    Topology generated by a collection of subsets of ##X##

    Homework Statement . Let ##X## be a set and ##\mathcal A \subset \mathcal P(X)##. Prove that there is a topology ##σ(A)## on ##X## that satisfies (i) every element of ##A## is open for ##σ(A)## (ii) if ##\tau## is a topology on ##X## such that every element of ##\mathcal A## is open for...
  24. perplexabot

    Can I buy pre-made balun transformers for a double balanced ring diode mixer?

    Hi all. I started a thread a while back about RF mixer design. I didn't know what to do or what design to choose. You guys laid some options for me and after some research and time I have finally decided that I will go for a double balanced, ring diode topology. Here is a schematic from google...
  25. M

    Topology on a set ##X## (find interior, closure and boundary of sets)

    Homework Statement . Let ##X## be a nonempty set and let ##x_0 \in X##. (a) ##\{U \in \mathcal P(X) : x_0 \in U\} \cup \{\emptyset\}## is a topology on ##X##. (b) ##\{U \in \mathcal P(X) : x_0 \not \in U\} \cup \{X\}## is a topology on ##X##. Describe the interior, the closure and the...
  26. Greg Bernhardt

    Definition of Topology: What is a Topological Space?

    Definition/Summary A Topological Space can be defined as a non empty set X along with a class of sets, called a topology on X which is closed under (1) arbitrary unions (2) finite intersections. It can be assumed that this will always include X and p (the empty set), but understanding the...
  27. C

    Consequences of a Codimension One and One-Dimensional Foliations on Topology

    I was suprised to realize that foliation theory was actually closely related to topology. Indeed, http://www.map.mpim-bonn.mpg.de/Foliations, states a theorem which say that a codimension one foliation exists if and only if the Euler characteristic of the topological space is one! I am...
  28. C

    Intuition on "giving a set a topology".

    The intuitive picture I have of giving a set a topology, is that of giving it a shape in the sense of connecting the points and determining what points lie next to each other (continuity), the numbers of holes of the shape, and what parts of it are connected to what. However, the most...
  29. Radarithm

    Need an introductory topology textbook

    I've been thinking about this for around 7 months now, which is way too much; Munkres seems like the "typical" introduction to topology book (kind of like how Griffiths is the "typical" E&M text), and various people (from the reviews over at Amazon) make it seem like it is an undergraduate level...
  30. Math Amateur

    MHB Visualising Topology: How Important is it to Get the Visualisation Clear?

    I am reading myself into a basic understanding go topology with a view to algebraic topology. I try to get a visual picture and intuitive feel for what I am learning .. but wonder if I am worrying too much about gaining this type of understanding early on ... For example I am at the moment...
  31. Math Amateur

    Mobius Band as a Quotient Topology

    I am reading Martin Crossley's book, Essential Topology. I am at present studying Example 5.55 regarding the Mobius Band as a quotient topology. Example 5.55 Is related to Examples 5.53 and 5.54. So I now present these Examples as follows: I cannot follow the relation (x,y) \sim (x', y')...
  32. Math Amateur

    Simple topology problem involving continuity

    Example 1 in James Munkres' book, Topology (2nd Edition) reads as follows: Munkres states that the map p is 'readily seen' to be surjective, continuous and closed. My problem is with showing (rigorously) that it is indeed true that the map p is continuous and closed. Regarding the...
  33. Math Amateur

    MHB What are some recommended texts for studying algebraic topology?

    I have a basic (very basic :)) understanding of the elements of algebra and many years ago I did a course in analysis ... and I would very much like to read my way to an understanding of algebraic topology .. I figured I should start with some basic texts on topology that (hopefully) head...
  34. W

    Should I learn Algebraic Topology?

    I'm a phyiscs student and I have been looking at these lectures: https://www.youtube.com/playlist?list=PL6763F57A61FE6FE8 But I have never learned anything about topology before and was he covers doesn't look like the Topology chapter in my mathematical physics book. I was looking for...
  35. T

    What Defines a Ball, Interior, and Limit Point in Metric Spaces?

    Homework Statement For a metric space (X,d) and a subset E of X, de fine each of the terms: (i) the ball B(p,r), where pεX and r > 0 (ii) p is an interior point of E (iii) p is a limit point of E Homework Equations The Attempt at a Solution i) Br(p) = {xεX: d(x.p)≤r}...
  36. O

    Is there any intro topics involving topology and physics?

    I have recently been assigned a project in my undergraduate topology class. I would like to do something in physics which involves topology, but I am having trouble finding a basic topic. I understand that there are some very advanced topics in string theory and the like, but I would like to...
  37. C

    Definition of a circle in point set topology.

    The circle seems to be of great importance in topology where it forms the basis for many other surfaces (the cylinder ##\mathbb{R}\times S^1##, torus ##S^1 \times S^1## etc.). But how does one define the circle in point set topology? Is it any set homeomorphic to the set ##\left\{(x,y) \in...
  38. R136a1

    Naber's Topology, geometry and gauge fields and similar books

    Hello, This thread is about the two books by Naber: https://www.amazon.com/dp/1461426820/?tag=pfamazon01-20 https://www.amazon.com/dp/0387989471/?tag=pfamazon01-20 The topics in this book seem excellent. They are standard mathematical topics such as homotopy, homology, bundles...
  39. N

    [algebraic topology] proving local degree is +1

    Homework Statement Suppose we have f: \mathbb C^n \to \mathbb C^n with f(z_1, \cdots,z_n) = (\sigma_1(\mathbf z), \cdots, \sigma_n(\mathbf z)) where the sigmas are the elementary symmetric functions (i.e. \sigma_1 = \sum z_j \quad \sigma_2 = \sum_{i < j} z_i z_j \quad etc) Note if we look...
  40. N

    How do axioms for Euclidean geometry exclude non-trivial topology?

    Think for example of the torus as a square with the proper edges identified. Viewed like this (i.e. using the flat metric), it clearly has zero curvature everywhere. More specifically, it seems Euclid's axioms are satisfied. But however we have non-trivial topology. So what's up? Or is...
  41. M

    Statement about topology of subsets of a metric space.

    Homework Statement . Prove that a closed subset in a metric space ##(X,d)## is the boundary of an open subset if and only if it has empty interior. The attempt at a solution. I got stuck in both implications: ##\implies## Suppose ##F## is a closed subspace with ##F=\partial S## for some...
  42. AdrianHudson

    Finding Topology Books for Beginners

    Hello :) I am looking for some books for an intro to topology and what other books I need to supplement my readings not quite sure the prereqs for topology but I am willing to learn the stuff needed thank you! P.S Physical textbooks are what I am looking for but if that's not available then...
  43. D

    Show that the half open interval is a topology

    Homework Statement We are given ##H## = {##O | \forall x, \exists a,b \in R## s.t ##x \in [a,b] \subseteqq O##}##\bigcup {\oslash}## and are asked to show that it is a topology on R Homework Equations Definition of a topological space The Attempt at a Solution I am trying to...
  44. V

    Definition of a subbasis of a topology

    One of the definitions of a subbasis ##\mathcal{S}## of a set ##X## is that it covers ##X##. Then the collection of all unions of finite intersections of elements of ##\mathcal{S}## make up a topology ##\mathcal{T}## on ##X##. That means the collection of all finite intersections of elements of...
  45. T

    General topology of a two terminal electrical device

    There are several possible topologies for an electrical circuit. However, if we limit our circuit to be a two terminal device, how will this limit the options for the different topologies? I am a beginner in this field, but as far as I can tell by drawing the circuits, the only possible...
  46. V

    Is the empty set always part of the basis of a topology?

    The topology ## T ## on a set ## X ## generated by a basis ## B ## is defined as: T=\{U\subset X:\forall\ x\in U\ there\ is\ a\ \beta\in B:x\in \beta \ and\ \beta\subset U \}. But if ##U## is the empty set, and there has to be a ## \beta ## in ##B## that is contained in ##U##, the empty set...
  47. D

    Is analysis necessary to know topology and differential geometry?

    I'm a physics major interested in taking some upper level math classes such as topology, differential geometry, and group theory but these classes are only taught in the math department and are heavy on the proofs. Analysis are recommended and preferred prerequisites but are apparently not...
  48. T

    Showing the connectedness of a product topology

    Let A be a proper subset of X, and let B be a proper subset of Y . If X and Y are connected, show that X × Y − A × B is connected. Attempt: Proven before in my book, I know that since X and Y are each connected that X x Y is also connected. Keeping that fact in mind. Pf: Assume (X x Y) -...
  49. S

    Topology of (Anti) de Sitter space

    Almost every book that I can think of derives the de Sitter spacetime as a hyperboloid in a (4+1) D spacetime, with the topology ℝ \times S^3, but I'm having trouble finding something justifying it. "Exact solutions of Einstein's Field Equations" gives what seems like an ℝ^{4} version : ds^2...
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