Contractible Website Links For
Space
 

Information About

Contractible




For example, any Convex Subset of Euclidean Space is contractible. On the other hand, Spheres of any finite dimension are not contractible.

Since a contractible space is homotopy equivalent to a point, all the Homotopy Group s of a contractible space are Trivial . Therefore any space with a nontrivial homotopy group cannot be contractible.

For a topological space ''X'' the following are all equivalent (here ''Y'' is an arbitrary topological space):
  • ''X'' is contractible (i.e. the identity map is null-homotopic).

  • ''X'' is homotopy equivalent to a one-point space.

  • Any two maps ''f'',''g'' : ''Y'' → ''X'' are homotopic.

  • Any map ''f'' : ''Y'' → ''X'' is null-homotopic.

  • Any map ''f'' : ''X'' → ''Y'' is null-homotopic.


Any space which Deformation Retract s onto a point is clearly contractible. The converse, however, is false. There are examples of contractible spaces which do not deformation retract onto any point.

The Cone on a space ''X'' is always contractible. Therefore any space can be embedded in a contractible one.

Furthermore, ''X'' is contractible if and only if there exists a Retraction from the cone of ''X'' to ''X''.