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Download as PDF; Printable version; ... Lindelöf's lemma is a simple but useful lemma in topology on the real line, ... M.A. Armstrong (1983), Basic Topology, ...
In mathematics, general topology (or point set topology) is the branch of topology that deals with the basic set-theoretic definitions and constructions used in topology. It is the foundation of most other branches of topology, including differential topology , geometric topology , and algebraic topology .
A three-dimensional model of a figure-eight knot.The figure-eight knot is a prime knot and has an Alexander–Briggs notation of 4 1.. Topology (from the Greek words τόπος, 'place, location', and λόγος, 'study') is the branch of mathematics concerned with the properties of a geometric object that are preserved under continuous deformations, such as stretching, twisting, crumpling ...
M. A. Armstrong, Basic Topology, Springer-Verlag, 1983 Sasho Kalajdzievski, An Illustrated Introduction to Topology and Homotopy , CRC Press, 2010, Chapter 10: Isotopy and Homotopy This topology-related article is a stub .
For example, the Euclidean topology on the plane admits as a base the set of all open rectangles with horizontal and vertical sides, and a nonempty intersection of two such basic open sets is also a basic open set. But another base for the same topology is the collection of all open disks; and here the full (B2) condition is necessary.
Absolutely closed See H-closed Accessible See . Accumulation point See limit point. Alexandrov topology The topology of a space X is an Alexandrov topology (or is finitely generated) if arbitrary intersections of open sets in X are open, or equivalently, if arbitrary unions of closed sets are closed, or, again equivalently, if the open sets are the upper sets of a poset.
A key concept in defining simplicial homology is the notion of an orientation of a simplex. By definition, an orientation of a k-simplex is given by an ordering of the vertices, written as (v 0,...,v k), with the rule that two orderings define the same orientation if and only if they differ by an even permutation.
Cauchy space – Concept in general topology and analysis; Convergence space – Generalization of the notion of convergence that is found in general topology; Filters in topology – Use of filters to describe and characterize all basic topological notions and results. Sequential space – Topological space characterized by sequences