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retract, retraction

Let X$ and Y$ be continua. A mapping f: X \to Y$ is said to be a retraction provided that Y \subset X$ and the restriction f\vert Y: Y \to f(Y) \subset X$ is the identity; then Y$ is called a retract of X$.
next up previous contents index
Next: rigid Up: Definitions Previous: regular
Janusz J. Charatonik, Pawel Krupski and Pavel Pyrih
2001-11-30