Definition:Jordan Curve/Also defined as

From ProofWiki
Jump to navigation Jump to search

Jordan Curve: Also defined as

Some texts change the definition of the codomain of a Jordan curve from $\R^2$ to $X$, where $X$ is alternatively defined as:

This is what $\mathsf{Pr} \infty \mathsf{fWiki}$ defines as an simple loop.


Some texts drop the condition that $\map f 0 = \map f 1$ and replace it with the condition:

$\map f t \ne \map f 1$ for all $t \in \openint 0 1$

which means they consider a Jordan arc to be a Jordan curve.


Some texts, especially those on topology, define a Jordan curve as a topological subspace $\struct{C, \tau_C}$ of $\R^2$ or $X$, where $\struct{C, \tau_C}$ is homeomorphic to the unit circle $\mathbb S^1$.

Jordan Curve Image Equals Set Homeomorphic to Circle shows the connection between the definition of Jordan curve as a path, and the definition as a topological space.


Sources