Difference between revisions of "871 - Topology"
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===Compactness=== | ===Compactness=== | ||
| + | :''see also:'' [[Compact]] | ||
===Separation Properties === | ===Separation Properties === | ||
Revision as of 19:05, 7 December 2022
Contents
Homeomorphism Invariants
Metrizability
Connectedness
Path Connected
Compactness
- see also: Compact
Separation Properties
\(T_1 \)
A topological space \(X \) is \(T_1 \) if for any two distinct points \( a,b\in X\) there are open sets \( U,V\) in \(X \) with \(a\in U, b\not \in U, a\not\in V, b\in V \).
\(T_2 \) (Hausdorff)
- See also T2 (Hausdorff)
\(T_3 \) (Regular)
A topological space \(X \) is \(T_3 \) if it is \(T_1 \) and for any point \( a \in X\) and closed set \(B \in X \) with \(a \not \in B \), there are disjoint open sets \(U,V \in X \) with \(a\in U \) and \(B\sube V \)
\(T_4 \) (Normal)
A topological space \(X \) is \(T_4 \) if it is \(T_1 \)and for any two disjoint closed sets \(A,B \in X \) there are disjoint open sets \(U,V \in X \) with \( A \sube U\) and \(B \sube V \).
