Displaying similar documents to “A proof (involving Martin's axiom) of a partition relation”

On Monk’s questions

Saharon Shelah (1996)

Fundamenta Mathematicae

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We deal with Boolean algebras and their cardinal functions: π-weight π and π-character πχ. We investigate the spectrum of π-weights of subalgebras of a Boolean algebra B. Next we show that the π-character of an ultraproduct of Boolean algebras may be different from the ultraproduct of the π-characters of the factors.

On Todorcevic orderings

Bohuslav Balcar, Tomáš Pazák, Egbert Thümmel (2015)

Fundamenta Mathematicae

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The Todorcevic ordering 𝕋(X) consists of all finite families of convergent sequences in a given topological space X. Such an ordering was defined for the special case of the real line by S. Todorcevic (1991) as an example of a Borel ordering satisfying ccc that is not σ-finite cc and even need not have the Knaster property. We are interested in properties of 𝕋(X) where the space X is taken as a parameter. Conditions on X are given which ensure the countable chain condition and its...