next up previous contents index
Next: rigid Up: Definitions Previous: regular

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.

Janusz J. Charatonik, Pawel Krupski and Pavel Pyrih
2001-02-21