Ideal games, Ramsey sets and the Frechet-Urysohn property
msra(2010)
摘要
It is shown that Matet's characterization of $\mathcal{H}$-Ramseyness
relative to a selective coideal $\mathcal{H}$, in terms of games of Kastanas,
still holds if we consider semiselectivity instead of selectivity. Moreover, we
prove that a coideal $\mathcal{H}$ is semiselective if and only if Matet's
game-theoretic characterization of $\mathcal{H}$-Ramseyness holds. This gives a
game-theoretic counter part to a theorem of Farah, asserting that a coideal
$\mathcal{H}$ is semiselective if and only if the family of
$\mathcal{H}$-Ramsey subsets of $\mathbb{N}^{[\infty]}$ coincides with the
family of those sets having the $Exp(\mathcal{H})$-Baire property. Finally, we
show that under suitable assumptions, semiselectivity is equivalent to the
Fr\'echet-Urysohn property.
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关键词
ramsey theory,frechet-urysohn property,semiselective ideal,banach-mazur games.,baire property
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