
The authors prove two theorems about totally imperfect subsets of \(2^\omega\). The first theorem deals with the notion of dual Ramsey set introduced by \textit{T. J. Carlson} and \textit{S. G. Simpson} [Adv. Math. 53, 265--290 (1984; Zbl 0564.05005)]. Here it is proved that every strongly meager subset of \(2^{\omega \times \omega}\) is dual Ramsey null. In the second part of the paper the authors introduce the following definition: a \(\sigma\)-ideal \(\mathcal I\) of subsets of \(2^\omega\) has property (\ddag) if every \(X \subseteq 2^{\omega}\) such that for every \(f \in \omega^{\uparrow \omega}\) the set \(\{g \in \omega^{\uparrow \omega} : f \nprec g\} \cap X \in \mathcal I\) belongs to \(\mathcal I\). Then they prove that each of the following three \(\sigma\)-ideals has property (\ddag): perfectly meager sets, universally meager sets, and perfectly meager sets in the transitive sense. As a corollary of the last of these results it is proved, assuming CH, the existence of a perfectly meager set in the transitive sense which is not completely Ramsey null and of a perfectly meager set in the transitive sense which is not an \(l_0\) set (the latter notion is related to Laver forcing).
Other connections with logic and set theory, strongly meager sets, dual Ramsey null sets, Other classical set theory (including functions, relations, and set algebra), partitions, strongly meager set, Descriptive set theory
Other connections with logic and set theory, strongly meager sets, dual Ramsey null sets, Other classical set theory (including functions, relations, and set algebra), partitions, strongly meager set, Descriptive set theory
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