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homotopy of maps (Definition)

Let $ X,Y$ be topological spaces, $ A$ a closed subspace of $ X$ and $ f,g:X \to Y$ continuous maps. A homotopy of maps is a continuous function $ F:X \times [0,1] \to Y$ satisfying

  1. $ F(x,0)=f(x)$ for all $ x \in X$
  2. $ F(x,1)=g(x)$ for all $ x \in X$
  3. $ F(x,t)=f(x)=g(x)$ for all $ x \in A, t\in [0,1]$.
We say that $ f$ is homotopic to $ g$ relative to $ A$ and denote this by $ f \simeq g$ $ rel A$. If $ A=\emptyset$, this can be written $ f \simeq g$. If $ g$ is the constant map (i.e. $ g(x)=y$ for all $ x \in X$), then we say that $ f$ is nullhomotopic.



"homotopy of maps" is owned by mathcam. [ full author list (2) | owner history (1) ]
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See Also: homotopy of paths, homotopy equivalence, constant function, contractible

Other names:  homotopic maps
Also defines:  homotopic, nullhomotopic
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Cross-references: constant map, continuous maps, subspace, closed, topological spaces
There are 32 references to this entry.

This is version 8 of homotopy of maps, born on 2002-01-23, modified 2008-05-27.
Object id is 1584, canonical name is HomotopyOfMaps.
Accessed 7421 times total.

Classification:
AMS MSC55Q05 (Algebraic topology :: Homotopy groups :: Homotopy groups, general; sets of homotopy classes)

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