Definition:Retraction (Topology)
Jump to navigation
Jump to search
Definition
Let $T_1 = \struct {S_1, \tau_1}$ be a topological space.
Let $T_2 = \struct {S_2, \tau_2}$ be a topological subspace of $T_1$.
That is:
- $S_2 \subseteq S_1$
Let $f: S_1 \to S_2$ be a mapping.
Then $f$ is retraction of $T_1$ if and only if
- $\forall s \in S_2: \map f s = s$
Also see
Sources
- 1989: Ephraim J. Borowski and Jonathan M. Borwein: Dictionary of Mathematics ... (previous) ... (next): retraction
- Mizar article BORSUK_1:def 16