Displaying similar documents to “Remarks on measurable Boolean algebras and sequential cardinals”

Cellularity of free products of Boolean algebras (or topologies)

Saharon Shelah (2000)

Fundamenta Mathematicae

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The aim this paper is to present an answer to Problem 1 of Monk [10], [11]. We do this by proving in particular that if μ is a strong limit singular cardinal, θ = ( 2 c f ( μ ) ) + and 2 μ = μ + then there are Boolean algebras 𝔹 1 , 𝔹 2 such that c ( 𝔹 1 ) = μ , c ( 𝔹 2 ) < θ b u t c ( 𝔹 1 * 𝔹 2 ) = μ + . Further we improve this result, deal with the method and the necessity of the assumptions. In particular we prove that if 𝔹 is a ccc Boolean algebra and μ ℶ ω ≤ λ = c f ( λ ) ≤ 2 μ then 𝔹 satisfies the λ-Knaster condition (using the “revised GCH theorem”).

A new proof of Kelley's Theorem

S. Ng (1991)

Fundamenta Mathematicae

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Kelley's Theorem is a purely combinatorial characterization of measure algebras. We first apply linear programming to exhibit the duality between measures and this characterization for finite algebras. Then we give a new proof of the Theorem using methods from nonstandard analysis.

Prenormality of ideals and completeness of their quotient algebras

A. Morawiec, B. Węglorz (1993)

Colloquium Mathematicae

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It is well known that if a nontrivial ideal ℑ on κ is normal, its quotient Boolean algebra P(κ)/ℑ is κ + -complete. It is also known that such completeness of the quotient does not characterize normality, since P(κ)/ℑ turns out to be κ + -complete whenever ℑ is prenormal, i.e. whenever there exists a minimal ℑ-measurable function in κ κ . Recently, it has been established by Zrotowski (see [Z1], [CWZ] and [Z2]) that for non-Mahlo κ, not only is the above condition sufficient but also necessary...