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Set-Theoretic Topology

Alan Dow

Subevent of Set-Theoretic Topology - Thurs. AM

Forbes 2070C

Eastern Time (US & Canada)

Starts at: 2025-03-06 10:40AM

Ends at: 2025-03-06 11:00AM

Discrete density number

Alan Dow ⟨adow@charlotte.edu⟩

Abstract:

A subset $D$ is a discretely dense subset of a space $X$ if every point of $X$ is in the closure of a discrete subset of $D$. The cardinal invariant, $Dd(X)$, was introduced by Juhasz and is the minimum cardinality of a discretely dense subset of $X$. We are reporting on some recent work with Juhasz and van Mill on results that improve upon the, seemingly only, obvious inequalities $d(X)\leq Dd(X)\leq |X|$. We also consider, $Fd(X)$, the free sequence density number.

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