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Characterizations of ideal cluster points

  • Paolo Leonetti ORCID logo EMAIL logo and Fabio Maccheroni
From the journal Analysis

Abstract

Given an ideal on ω, we prove that a sequence in a topological space X is -convergent if and only if there exists a “big” -convergent subsequence. Then we study several properties and show two characterizations of the set of -cluster points as classical cluster points of a filter on X and as the smallest closed set containing “almost all” the sequence. As a consequence, we obtain that the underlying topology τ coincides with the topology generated by the pair (τ,).

Acknowledgements

The authors are grateful to Szymon Głab (Łódź University of Technology, PL) and Ondřej Kalenda (Charles University, Prague) for several useful comments.

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Received: 2018-12-30
Accepted: 2019-02-04
Published Online: 2019-02-26
Published in Print: 2019-03-01

© 2019 Walter de Gruyter GmbH, Berlin/Boston

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