Results 11 to 20 of about 6,858,530 (350)

Ultrafilters on a countable set

Annals of Mathematical Logic, 1970
An ultrafilter on a set is a proper collection of subsets of ' that set which is maximal among such collections having the finite intersection property. Ultrafilters were popularized by N.Bourbaki for their use in describing topological convergence, but for some time there was little discussion of the possible structural properties that an indiwdual ...
David Booth
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On the structure of measurable filters on a countable set [PDF]

, 1999
A combinatorial characterization of measurable filters on a countable set is found. We apply it to the problem of measurability of the intersection of nonmeasurable filters.
T. Bartoszynski
semanticscholar   +2 more sources

Conformal Equivalence of Countable Dense Sets [PDF]

Proceedings of the American Mathematical Society, 1967
In [1, p. 297, problem 24], Erd6s asks: "Does there exist an entire functionf, not of the form f(z) = ao+aiz, such that the number f(x) is rational or irrational according as x is rational or irrational? More generally, if A and B are two denumerable, dense sets, does there exist an entire function which maps A onto B?" The following theorem settles ...
Wolfgang Maurer
openaire   +3 more sources

Uncountable graphs and invariant measures on the set of universal countable graphs [PDF]

Random Struct. Algorithms, 2008
We give new examples and describe the complete lists of all measures on the set of countable homogeneous universal graphs and Ks‐free homogeneous universal graphs (for s ≥ 3) that are invariant with respect to the group of all permutations of the ...
F. Petrov, A. Vershik
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A countable set derived by fuzzy set [PDF]

, 2015
In this paper, it shows that for each fuzzy set $u$ on $\mathbb{R}^m$, the set $D(u)$ is at most countable. Based on this, it modifies the proof of assertion (I) in step 2 of the sufficiency part of Theorem 4.1 in paper: Characterizations of compact sets in fuzzy sets spaces with $L_p$ metric, http://arxiv.org/abs/1509.00447.
Huan Huang
openaire   +3 more sources

Analytic topologies over countable sets

Topology and its Applications, 2001
The subject of the paper is the systematic study of analytic topologies over the set of natural numbers \(\mathbb N\) (every topology over \(\mathbb N\) is identified with a subset of the Cantor space \(2^{\mathbb N}\)). The authors analyze closed and \(G_\delta\) topologies, topologies that have the Baire property and \(T_1\) topologies.
Todorčević, Stevo, Uzcátegui, Carlos
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A sufficient condition for countable-set aposyndesis [PDF]

, 1972
D. Bennett
semanticscholar   +2 more sources

COUNTABLY PERFECTLY MEAGER SETS [PDF]

The Journal of Symbolic Logic, 2021
AbstractWe study a strengthening of the notion of a perfectly meager set. We say that a subset A of a perfect Polish space X is countably perfectly meager in X, if for every sequence of perfect subsets $\{P_n: n \in \mathbb N\}$ of X, there exists an $F_\sigma $ -set F in X such that $A \subseteq F$ and $F\cap P_n$ is meager in $P_n$ for each ...
Pol, Roman, Zakrzewski, Piotr
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Ideals on countable sets: a survey with questions

Revista Integración, 2019
An ideal on a set X is a collection of subsets of X closed under the operations of taking finite unions and subsets of its elements. Ideals are a very useful notion in topology and set theory and have been studied for a long time.
Carlos Uzcátegui Aylwin
doaj   +2 more sources

Most-intersection of countable sets [PDF]

Journal of Applied Non-Classical Logics, 2021
12 ...
Çevik, Ahmet, Topal, Selçuk
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