On $s$-closedness and $\Cal S$-closedness in topological spaces


Zbigniew Duszy\'nski




Some properties of sets $s$-closed or $\Cal S$-closed relative to a space, and $s$-closed or $\Cal S$-closed subspaces, are obtained. Relationships between some of them are indicated. New characterizations of Hausdorff spaces in terms of $s$-closedness and $\alpha$-compactness relative to a space, are obtained.