Cofinalities of countable ultraproducts: The existence theorem
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.
scientific article; zbMATH DE number 4135929