Anti-Chains of Mappings from omega^omega on some BQO
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Serval ID
serval:BIB_FA2CB02AE2CF
Type
Unpublished: a document having an author and title, but not formally published.
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Publications
Institution
Title
Anti-Chains of Mappings from omega^omega on some BQO
Language
english
Notes
temporary version, to be submitted
Abstract
Issue: Let (P,<) be some BQO. Louveau and Saint-Raymond showed that the following structure (F, <_F) is also a BQO: F={φ: from ωω into P: φ is Borel with countable image} with the usual topology on ωω and the discrete topology on the BQO P; and φ <_F ψ iff there exists some continuous function h: from ωω to ωω such that for all x ∈ ωω φ(x) < ψ(h(x)). The following proposition answers the question of the relation between cardinalities of anti-chains of P and anti-chains of F: 1) Every anti-chain in P has cardinality 1 ⇒ every anti-chain in F has cardinality 1. 2) There exists an anti-chain in P of cardinality 2, but no element of P is incomparable with two different elements ⇒ every anti-chain in F has cardinality at most 2. 3) There exists an element in P which is incomparable with two different elements ⇒ there exists anti-chains of any cardinality in F.
Create date
23/01/2008 19:40
Last modification date
20/08/2019 16:25