Article ID Journal Published Year Pages File Type
4662703 Annals of Pure and Applied Logic 2010 14 Pages PDF
Abstract

Let C(α)C(α) denote the class of all cardinal sequences of length αα associated with compact scattered spaces. Also put Cλ(α)={f∈C(α):f(0)=λ=min[f(β):β<α]}.Cλ(α)={f∈C(α):f(0)=λ=min[f(β):β<α]}.If λλ is a cardinal and α<λ++α<λ++ is an ordinal, we define Dλ(α)Dλ(α) as follows: if λ=ωλ=ω, Dω(α)={f∈α{ω,ω1}:f(0)=ω},Dω(α)={f∈α{ω,ω1}:f(0)=ω}, and if λλ is uncountable, Dλ(α)={f∈α{λ,λ+}:f(0)=λ,f−1{λ} is <λ-closed and successor-closed in α}. We show that for each uncountable regular cardinal λλ and ordinal α<λ++α<λ++ it is consistent with GCH that Cλ(α)Cλ(α) is as large as possible, i.e. Cλ(α)=Dλ(α).Cλ(α)=Dλ(α). This yields that under GCH for any sequence ff of regular cardinals of length αα the following statements are equivalent: (1)f∈C(α)f∈C(α) in some cardinal-preserving and GCH-preserving generic-extension of the ground model.(2)for some natural number nn there are infinite regular cardinals λ0>λ1>⋯>λn−1λ0>λ1>⋯>λn−1 and ordinals α0,…,αn−1α0,…,αn−1 such that α=α0+⋯+αn−1α=α0+⋯+αn−1 and f=f0⌢f1⌢⋯⌢fn−1 where each fi∈Dλi(αi)fi∈Dλi(αi).The proofs are based on constructions of universal locally compact scattered spaces.

Related Topics
Physical Sciences and Engineering Mathematics Logic
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