نتایج جستجو برای: zcirc ultrafilter
تعداد نتایج: 382 فیلتر نتایج به سال:
We continue the study started in [2] and characterize j↾V, where j:V[G]→M[H] is an ultrapower embedding by a normal ultrafilter after non-stationary support iteration of Prikry forcings.
An ultrafilter U is Hausdorff if for any two functions f, g ∈ ω ω , f (U) = g(U) iff f ↾X = g↾X for some X ∈ U. We will show that it is consistent that there are no Hausdorff ultrafilters.
We provide an exposition of supercompact Radin forcing and present several methods for iterating Radin forcing. In this paper we give an exposition of supercompact Radin forcing using coherent sequences of ultrafilters. This version of Radin forcing includes as special cases the Prikry forcing and Magidor forcing, both the measurable and supercompact versions. We also introduce some methods for...
We prove various results on the notion of ordinal ultrafiters introduced by J. Baumgartner. In particular, we show that this notion of ultrafilter complexity is independent of the more familiar Rudin-Keisler ordering.
We characterize winning strategies in various infinite games involving filters on the natural numbers in terms of combinatorics or structural properties of the given filter. These generalize several ultrafilter games of Galvin.
We prove that the number of near-coherence classes of non-principal ultrafilters on the natural numbers is either finite or at least the larger of the dominating number and the minimum number of generators for such an ultrafilter.
We prove that N has an uncountable elementary extension N such that there is no ultrafilter on the Boolean Algebra of subsets of N represented in N which is minimal (i.e. Ramsey for partitions represented in N).
The Stone-Čech compactification of the natural numbers βω (or equivalently, the space of ultrafilters on the subsets of ω) is a well-studied space with interesting properties. Replacing the subsets of ω by partitions of ω in the construction of the ultrafilter space gives non-homeomorphic spaces of partition ultrafilters corresponding to βω. We develop a general framework for spaces of this typ...
The category-theoretic nature of general frames for modal logic is explored. A new notion of “modal map” between frames is defined, generalizing the usual notion of bounded morphism/p-morphism. The category Fm of all frames and modal maps has reflective subcategories CHFm of compact Hausdorff frames, DFm of descriptive frames, and UEFm of ultrafilter enlargements of frames. All three subcategor...
The category-theoretic nature of general frames for modal logic is explored. A new notion of “modal map” between frames is defined, generalizing the usual notion of bounded morphism/p-morphism. The category Fm of all frames and modal maps has reflective subcategories CHFm of compact Hausdorff frames, DFm of descriptive frames, and UEFm of ultrafilter enlargements of frames. All three subcategor...
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