# Sh:677

• Shelah, S., & Spinas, O. (2000). On incomparability and related cardinal functions on ultraproducts of Boolean algebras. Math. Japon., 52(3), 345–358.
• Abstract:
Let C denote any of the following cardinal characteristics of Boolean algebras: incomparability, spread, character, \pi-character, hereditary Lindelöf number, hereditary density. It is shown to be consistent that there exists a sequence \langle B_i:i<\kappa\rangle of Boolean algebras and an ultrafilter D on \kappa such that C(\prod_{i<\kappa}B_i/D)<|\prod_{i<\kappa}C(B_i)/D|. This answers a number of problems posed by Monk.
• Version 2000-06-08_10 (16p)
Bib entry
@article{Sh:677,
author = {Shelah, Saharon and Spinas, Otmar},
title = {{On incomparability and related cardinal functions on ultraproducts of Boolean algebras}},
journal = {Math. Japon.},
fjournal = {Mathematica Japonica},
volume = {52},
number = {3},
year = {2000},
pages = {345--358},
issn = {0025-5513},
mrnumber = {1796651},
mrclass = {03E35 (03E05 03E55 03G05 06E05)},
note = {\href{https://arxiv.org/abs/math/9903116}{arXiv: math/9903116}},
arxiv_number = {math/9903116}
}