Characterization of D-separable compact spaces and equality of cardinal invariants

From papers

Let XX be a compact space. A

disjoint-disjoint

-base is a

-base that is a countable union of pairwise disjoint collections. Let $d\delta(X)$ be the least cardinal

such that every dense subset of XX is the union of

many discrete sets, and let $d\pi(X)$ be the least cardinal

such that XX has a

basethatistheunionof-base that is the union of

many disjoint collections.

Characterization and cardinal-invariant conjecture. \begin{enumerate} \item A compact space XX is D-separable if and only if XX has a σ\sigma-disjoint π\pi-base. \item For every compact space XX, dδ(X)=dπ(X)d\delta(X)=d\pi(X). \end{enumerate}

These problems ask for a characterization of D-separability for compact spaces and for an equality between two cardinal invariants associated with discrete decompositions of dense sets and π\pi-bases. The supplied text presents them as open problems and gives no resolution.

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Sources & referencesView supporting material

Primary source

Angelo Bella, Mikhail Matveev and Santi Spadaro, “Variations of selective separability II: discrete sets and the influence of convergence and maximality”, arXiv:1101.4615 (2011).

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