closed sets and group actions.
28683
Sum of two closed sets in $\mathbb R$ is closed?
49703
Analogue of closed graph theorem
80860
How to call a space in which every G$_\kappa$-set is open
154682
G/H is Hausdorff implies H is closed (General topology, Volume 1 by N. Bourbaki)
78117
Closed property of nonempty finite set
16654
Unions and Intersections of Open Sets are Open
111141
Why is every discrete subgroup of a Hausdorff group closed?
147350
Homeomorphism between $\prod X_i$ and the Cantor set
50026
Product of compact and closed in topological group is closed
146146
Proof that a closed subset of a compact space is a compact space
94825
Open set as a finite union of closed sets
102048
Closure of a compact set in Regular space $ X $
133179
Fixed points under action of conjugate group elements
57468
Continuous homorphisms between topological groups.
58076
Subgroup generated by a set
99341
Basic question: closure of irreducible sets
27661
The closed graph theorem in topology