Path-connected-weakly open subset
This article defines a property over pairs of a topological space and a subspace, or equivalently, properties over subspace embeddings (viz, subsets) in topological spaces
This term is nonstandard and is being used locally within the wiki. For its use outside the wiki, please define the term when using it.
Definition
A subset of a topological space is termed path-connected-weakly open if it satisfies the following equivalent conditions:
- Given any continuous map from a path-connected space to the given topological space, the inverse image of the subset is open
- The subset is a union of some of the path-components of some open subset containing it
Significance
We can replace open subsets with path-connected-weakly open subsets, for homology computation tools like Mayer-Vietoris homology sequence and excision.