# Sh:415

• Koppelberg, S., & Shelah, S. (1995). Densities of ultraproducts of Boolean algebras. Canad. J. Math., 47(1), 132–145.
• Abstract:
We answer three problems by J. D. Monk on cardinal invariants of Boolean algebras. Two of these are whether taking the algebraic density \pi(A) resp. the topological density d(A) 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.
• published version (14p)
Bib entry
@article{Sh:415,
author = {Koppelberg, Sabine and Shelah, Saharon},
title = {{Densities of ultraproducts of Boolean algebras}},
journal = {Canad. J. Math.},
fjournal = {Canadian Journal of Mathematics. Journal Canadien de Math\'ematiques},
volume = {47},
number = {1},
year = {1995},
pages = {132--145},
issn = {0008-414X},
mrnumber = {1319693},
mrclass = {03C20 (03E10 03G05 06E05)},
doi = {10.4153/CJM-1995-007-0},
note = {\href{https://arxiv.org/abs/math/9404226}{arXiv: math/9404226}},
arxiv_number = {math/9404226}
}