Search results for "Regular space"
showing 3 items of 3 documents
On product of p-sequential spaces
2016
Abstract The product of finitely many regular p-compact p-sequential spaces is p-compact p-sequential for any free ultrafilter p as it follows from [5] . In the paper is produced an example of a Hausdorff p-compact p-sequential space whose square is not p-sequential. It is also given an example of a space which is sP-radial, wP-radial, vwP-radial for any P ⊂ μ ( τ ) but its square is neither sP-radial nor wP-radial nor vwP-radial space.
Countably compact weakly Whyburn spaces
2015
The weak Whyburn property is a generalization of the classical sequential property that was studied by many authors. A space X is weakly Whyburn if for every non-closed set \({A \subset X}\) there is a subset \({B \subset A}\) such that \({\overline{B} \setminus A}\) is a singleton. We prove that every countably compact Urysohn space of cardinality smaller than the continuum is weakly Whyburn and show that, consistently, the Urysohn assumption is essential. We also give conditions for a (countably compact) weakly Whyburn space to be pseudoradial and construct a countably compact weakly Whyburn non-pseudoradial regular space, which solves a question asked by Angelo Bella in private communica…
Upper bounds for the tightness of the $$G_\delta $$-topology
2021
We prove that if X is a regular space with no uncountable free sequences, then the tightness of its $$G_\delta $$ topology is at most the continuum and if X is, in addition, assumed to be Lindelof then its $$G_\delta $$ topology contains no free sequences of length larger then the continuum. We also show that, surprisingly, the higher cardinal generalization of our theorem does not hold, by constructing a regular space with no free sequences of length larger than $$\omega _1$$ , but whose $$G_\delta $$ topology can have arbitrarily large tightness.