Topology

Author

John Robin Inston

Published

September 25, 2026

1 Foundations

2 Sequences & Convergence

3 General (Point-Set) Topology

  • Topological Spaces - Open sets, bases, subbases
  • Neighborhoods and Limit Points
  • Continuity and Homeomorphisms
  • Separation Axioms
    • T0, T1, T2 (Hausdorff)
    • Regular and Normal Spaces
  • Countability Axioms
    • First and Second Countable Spaces
    • Separability
  • Compactness
    • Heine-Borel Theorem
    • Sequential Compactness
    • Local and σ-Compactness
    • Compactification (Alexandroff, Stone–Čech)
  • Connectedness
    • Path-Connectedness
    • Connected Components
  • Product, Subspace, and Quotient Topologies
  • Baire Category Theorem
  • Urysohn’s Lemma & Tietze Extension Theorem

4 Metric & Normed Spaces

  • Metric Spaces
  • Inner Product Space
  • Normed Vector Spaces
  • Banach Spaces
  • Hilbert Spaces
  • Completions of Metric Spaces
  • Contraction Mapping / Banach Fixed-Point Theorem

5 Algebraic Topology

  • Homotopy Theory
    • Homotopy Equivalence
    • Fundamental Group
    • Higher Homotopy Groups
  • Covering Spaces
  • Homology Theory
    • Simplicial Homology
    • Singular Homology
    • Cellular Homology
  • Cohomology
  • CW Complexes
  • Euler Characteristic

6 Differential Topology

  • Manifolds
    • Smooth Manifolds, Charts, Atlases
    • Manifolds with Boundary
  • Tangent Spaces and Tangent Bundles
  • Differential Forms
  • Vector Fields and Flows
  • Sard’s Theorem, Degree Theory

7 Functional-Analytic Topology

  • Weak and Weak-* Topologies
  • Compact Operators
  • Dirichlet Forms
  • Infinite-Dimensional Topological Vector Spaces

8 Applications

  • Topological Data Analysis - Persistent Homology
  • Stochastic Topology and Random Geometry - Random graphs, geometric complexes
  • Topology in Dynamical Systems

9 ## Key References

10 Backlinks

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