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Primal topologies on the integers
Given an infinite set X and a function f : X → X, the primal topology on X induced by f is the topology τ f = {U ⊆ X : f −1 (U ) ⊆ U}. In this paper, we prove that there are 2 ω pairwise non-homemomorphic primal topologies on ℕ. We also prove that an infinite set cannot have more than 2 ω pairwise n...
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Published in: | Quaestiones mathematicae 2021-04, Vol.44 (4), p.435-445 |
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Main Authors: | , , |
Format: | Article |
Language: | English |
Subjects: | |
Citations: | Items that this one cites Items that cite this one |
Online Access: | Get full text |
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Summary: | Given an infinite set X and a function f : X → X, the primal topology on X induced by f is the topology τ
f
= {U ⊆ X : f
−1
(U ) ⊆ U}. In this paper, we prove that there are 2
ω
pairwise non-homemomorphic primal topologies on ℕ. We also prove that an infinite set cannot have more than 2
ω
pairwise non-homeomorphic primal topologies. We give a necessary and sufficient condition to guarantee that an Alexandroff topology be n-resolvable for an 2 ≤ n ∈ ℕ. Other results on primal topologies are also given. |
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ISSN: | 1607-3606 1727-933X |
DOI: | 10.2989/16073606.2019.1695686 |