Add to ORKGsummary:We shall show that there is an ultrafilter on singular $\kappa$ with countable cofinality, which cannot be reached from the set of all subuniform ultrafilters by iterating the closure of sets of size $<\kappa$
AbstractAn important application of ultrafilters is in the ultraproduct construction in model theory...
Ultrafilters are very important mathematical objects in mathematical research [6, 22, 23]. There are...
Abstract. We investigate the structure of the Tukey types of ultrafilters on countable sets partiall...
summary:We shall show that there is an ultrafilter on singular $\kappa$ with countable cofinality, w...
This article surveys results regarding the Tukey theory of ultrafilters on countable base sets. The ...
. We prove some restrictions on the possible cofinalities of ultrapowers of the natural numbers wit...
AbstractLet D be a directed set without last element. Call an ultrafilter p on D cofinal if every se...
Abstract. We study Tukey types of ultrafilters on ω, focusing on the question of when Tukey reducibi...
AbstractWe study Tukey types of ultrafilters on ω, focusing on the question of when Tukey reducibili...
Abstract. Via two short proofs and three constructions, we show how to increase the model-theoretic ...
We prove the following: Theorem A. If D is a (λ +, κ)-regular ultrafilter, then either (a) D is (λ, ...
AbstractFor every cardinal κ ⩾ ω, the following is consistent: each x in U(κ) (the space of uniform ...
We show in the Zermelo-Fraenkel set theory ZF without the axiom of choice: Given an infinite set X, ...
AbstractInteraction between ultrafilters and uniformities on a countable set is investigated. Variou...
summary:We study some limitations and possible occurrences of uniform ultrafilters on ordinals witho...
AbstractAn important application of ultrafilters is in the ultraproduct construction in model theory...
Ultrafilters are very important mathematical objects in mathematical research [6, 22, 23]. There are...
Abstract. We investigate the structure of the Tukey types of ultrafilters on countable sets partiall...
summary:We shall show that there is an ultrafilter on singular $\kappa$ with countable cofinality, w...
This article surveys results regarding the Tukey theory of ultrafilters on countable base sets. The ...
. We prove some restrictions on the possible cofinalities of ultrapowers of the natural numbers wit...
AbstractLet D be a directed set without last element. Call an ultrafilter p on D cofinal if every se...
Abstract. We study Tukey types of ultrafilters on ω, focusing on the question of when Tukey reducibi...
AbstractWe study Tukey types of ultrafilters on ω, focusing on the question of when Tukey reducibili...
Abstract. Via two short proofs and three constructions, we show how to increase the model-theoretic ...
We prove the following: Theorem A. If D is a (λ +, κ)-regular ultrafilter, then either (a) D is (λ, ...
AbstractFor every cardinal κ ⩾ ω, the following is consistent: each x in U(κ) (the space of uniform ...
We show in the Zermelo-Fraenkel set theory ZF without the axiom of choice: Given an infinite set X, ...
AbstractInteraction between ultrafilters and uniformities on a countable set is investigated. Variou...
summary:We study some limitations and possible occurrences of uniform ultrafilters on ordinals witho...
AbstractAn important application of ultrafilters is in the ultraproduct construction in model theory...
Ultrafilters are very important mathematical objects in mathematical research [6, 22, 23]. There are...
Abstract. We investigate the structure of the Tukey types of ultrafilters on countable sets partiall...