Cofinalities of countable ultraproducts: The existence theorem
type: Item
instance of: scholarly article
title: Cofinalities of countable ultraproducts: The existence theorem
zbMATH Open document ID: 0694.03029
author: R. Michael Canjar
published in: Notre Dame Journal of Formal Logic
publication date: 1989-01-01T00:00:00Z
review text: The author shows that there exists an ultrafilter U on \(\omega\) such that the cofinality of the ultrapower \(^{\omega}\omega /U\) equals the cofinality of the minimal cardinality of any dominating family of \(^{\omega}\omega\). The coinitiality of the family of finite-to-one functions in this ultrapower is the same.
Mathematics Subject Classification ID: 03E05
zbMATH DE Number: 4135929
zbMATH Keywords: ultrafilter
zbMATH Keywords: cofinality
zbMATH Keywords: ultrapower
zbMATH Keywords: dominating family
zbMATH Keywords: coinitiality
zbMATH Keywords: finite-to-one functions
reviewed by: Neil H. Williams
MaRDI profile type: Publication
full work available at URL: https://doi.org/10.1305/ndjfl/1093635237
OpenAlex ID: W2014568148
DOI: 10.1305/NDJFL/1093635237
description: scientific article; zbMATH DE number 4135929