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Let X be a Polish space, and let C₀ and C₁ be disjoint coanalytic subsets of X. The pair (C₀,C₁) is said to be complete if for every pair (D₀,D₁) of disjoint coanalytic subsets of $ω^{ω}$ there exists a continuous function $f : ω^{ω} \to X$ such that $f^{- 1} (C ₀) = D ₀$ and $f^{- 1} (C ₁) = D ₁$ . We give several explicit examples of complete pairs of coanalytic sets.

Complete permutability of partitions in a set. I

Jitka Ševečková, František Šik (1989)

Archivum Mathematicum

Complete sequences of coanalytic sets

Riccardo Camerlo (2014)

Fundamenta Mathematicae

The notion of a complete sequence of pairwise disjoint coanalytic sets is investigated. Several examples are given and such sequences are characterised under analytic determinacy. The ideas are based on earlier results of Saint Raymond, and generalise them.

Complete subobjects of fuzzy sets over $M V$ -algebras

Jiří Močkoř (2004)

Czechoslovak Mathematical Journal

A subobjects structure of the category $Ω$ - of $Ω$ -fuzzy sets over a complete $M V$ -algebra $Ω = (L, \land, \lor, \otimes, \to)$ is investigated, where an $Ω$ -fuzzy set is a pair $𝐀 = (A, δ)$ such that $A$ is a set and $δ A \times A \to Ω$ is a special map. Special subobjects (called complete) of an $Ω$ -fuzzy set $𝐀$ which can be identified with some characteristic morphisms $𝐀 \to Ω^{*} = (L \times L, μ)$ are then investigated. It is proved that some truth-valued morphisms $\neg_{Ω} Ω^{*} \to Ω^{*}, \cap_{Ω}$ , $\cup_{Ω} Ω^{*} \times Ω^{*} \to Ω^{*}$ are characteristic morphisms of complete subobjects.

Completely nonmeasurable unions

Robert Rałowski, Szymon Żeberski (2010)

Open Mathematics

Assume that no cardinal κ < 2ω is quasi-measurable (κ is quasi-measurable if there exists a κ-additive ideal of subsets of κ such that the Boolean algebra P(κ)/ satisfies c.c.c.). We show that for a metrizable separable space X and a proper c.c.c. σ-ideal II of subsets of X that has a Borel base, each point-finite cover ⊆ $𝕀$ of X contains uncountably many pairwise disjoint subfamilies , with $𝕀$ -Bernstein unions ∪ (a subset A ⊆ X is $𝕀$ -Bernstein if A and X A meet each Borel $𝕀$ -positive subset...