The product-space conjecture for D-separability

Let XX be a topological space, and let d(X)d(X) denote its density and d(X)+d(X)^+ its successor cardinal. A space is D-separable if every sequence of dense subsets admits a choice of one point from each set such that the set of chosen points is dense.

Product-space conjecture. The space

Xd(X)+X^{d(X)^+}

is never D-separable.

This is presented as an open problem following the theorem that Xω1X^{\omega_1} is not D-separable for every separable space XX with at least two points, and that ds=ω1\mathfrak{ds}=\omega_1. The conjecture asks whether the exponent can generally be reduced to the successor of the density.

Sources & referencesView supporting material

Primary source

Daniel T. Soukup, Lajos Soukup and Santi Spadaro, “Comparing weak versions of separability”, arXiv:1210.4986 (2012).

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