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Seven characterizations of non-meager 𝖯-filters

Kenneth Kunen, Andrea Medini, Lyubomyr Zdomskyy (2015)

Fundamenta Mathematicae

We give several topological/combinatorial conditions that, for a filter on ω, are equivalent to being a non-meager -filter. In particular, we show that a filter is countable dense homogeneous if and only if it is a non-meager -filter. Here, we identify a filter with a subspace of 2 ω through characteristic functions. Along the way, we generalize to non-meager -filters a result of Miller (1984) about -points, and we employ and give a new proof of results of Marciszewski (1998). We also employ a theorem...

Skula spaces

Alan S. Dow, Stephen W. Watson (1990)

Commentationes Mathematicae Universitatis Carolinae

Some applications of the point-open subbase game

D. Guerrero Sánchez, Vladimir Vladimirovich Tkachuk (2017)

Commentationes Mathematicae Universitatis Carolinae

Given a subbase 𝒮 of a space X , the game P O ( 𝒮 , X ) is defined for two players P and O who respectively pick, at the n -th move, a point x n ∈ X and a set U n ∈ 𝒮 such that x n ∈ U n . The game stops after the moves { x n , U n : n ∈ ø } have been made and the player P wins if ⋃ n ∈ ø U n = X ; otherwise O is the winner. Since P O ( 𝒮 , X ) is an evident modification of the well-known point-open game P O ( X ) , the primary line of research is to describe the relationship between P O ( X ) and P O ( 𝒮 , X ) for a given subbase 𝒮 . It turns out that, for any subbase 𝒮 , the player P has a winning strategy...

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