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Densities of Ultraproducts of Boolean Algebras

Published online by Cambridge University Press:  20 November 2018

Sabine Koppelberg
Affiliation:
2. Mathematisches Institut der FU Berlin Arnimalee 3 14195 Berlin Germany sabina email: sabina@math.fu-berlin.de
Saharon Shelah
Affiliation:
Department of Mathematics Hebrew University Jerusalem, 910904 Israel email: shelah@math.huji.ac.il
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Abstract

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We answer three problems by J. D. Monk on cardinal invariants of Boolean algebras. Two of these are whether taking the algebraic density πA resp. the topological density cL4 of a Boolean algebra A commutes with formation of ultraproducts; the third one compares the number of endomorphisms and of ideals of a Boolean algebra.

Type
Research Article
Copyright
Copyright © Canadian Mathematical Society 1995

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