retract

Let $X$ be a topological space and $Y$ a subspace of $X$. If there exists a continuous map $r:X\to Y$ such that $r(y)=y$ for all $y\in Y$, then we say $Y$ is a retract of $X$ and $r$ is a retraction.

Title	retract
Canonical name	Retract
Date of creation	2013-03-22 12:16:06
Last modified on	2013-03-22 12:16:06
Owner	rspuzio (6075)
Last modified by	rspuzio (6075)
Numerical id	6
Author	rspuzio (6075)
Entry type	Definition
Classification	msc 54C15
Related topic	DeformationRetraction
Related topic	PeriodOfMapping
Defines	retraction