Ultrafilters on \(G\)-spaces

For a discrete group \(G\) and a discrete \(G\)-space \(X\), we identify the Stone-Cech compactifications \(\beta G\) and \(\beta X\) with the sets of all ultrafilters on \(G\) and \(X\), and apply the natural action of \(\beta G\) on \(\beta X\) to characterize large, thick, thin, sparse and scatte...

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Datum:2015
Hauptverfasser: Petrenko, O. V., Protasov, I. V.
Format: Artikel
Sprache:English
Veröffentlicht: Lugansk National Taras Shevchenko University 2015
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Online Zugang:https://admjournal.luguniv.edu.ua/index.php/adm/article/view/69
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Назва журналу:Algebra and Discrete Mathematics

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Algebra and Discrete Mathematics
id admjournalluguniveduua-article-69
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spelling admjournalluguniveduua-article-692015-09-28T11:22:08Z Ultrafilters on \(G\)-spaces Petrenko, O. V. Protasov, I. V. \(G\)-space, ultrafilters, ultracompanion, \(G\)-selective ultrafilter, \(G\)-Ramsey ultrafilter, \(T\)-point, ballean, asymorphism 05D10, 22A15, 54H20 For a discrete group \(G\) and a discrete \(G\)-space \(X\), we identify the Stone-Cech compactifications \(\beta G\) and \(\beta X\) with the sets of all ultrafilters on \(G\) and \(X\), and apply the natural action of \(\beta G\) on \(\beta X\) to characterize large, thick, thin, sparse and scattered subsets of \(X\). We use \(G\)-invariant partitions and colorings to define \(G\)-selective and \(G\)-Ramsey ultrafilters on \(X\). We show that, in contrast to the set-theoretical case, these two classes of ultrafilters are distinct. We consider also universally thin ultrafilters on \(\omega\), the \(T\)-points, and study interrelations between these ultrafilters and some classical ultrafilters on \(\omega\). Lugansk National Taras Shevchenko University 2015-09-28 Article Article Peer-reviewed Article application/pdf https://admjournal.luguniv.edu.ua/index.php/adm/article/view/69 Algebra and Discrete Mathematics; Vol 19, No 2 (2015) 2415-721X 1726-3255 en https://admjournal.luguniv.edu.ua/index.php/adm/article/view/69/18 Copyright (c) 2015 Algebra and Discrete Mathematics
institution Algebra and Discrete Mathematics
baseUrl_str
datestamp_date 2015-09-28T11:22:08Z
collection OJS
language English
topic \(G\)-space
ultrafilters
ultracompanion
\(G\)-selective ultrafilter
\(G\)-Ramsey ultrafilter
\(T\)-point
ballean
asymorphism
05D10
22A15
54H20
spellingShingle \(G\)-space
ultrafilters
ultracompanion
\(G\)-selective ultrafilter
\(G\)-Ramsey ultrafilter
\(T\)-point
ballean
asymorphism
05D10
22A15
54H20
Petrenko, O. V.
Protasov, I. V.
Ultrafilters on \(G\)-spaces
topic_facet \(G\)-space
ultrafilters
ultracompanion
\(G\)-selective ultrafilter
\(G\)-Ramsey ultrafilter
\(T\)-point
ballean
asymorphism
05D10
22A15
54H20
format Article
author Petrenko, O. V.
Protasov, I. V.
author_facet Petrenko, O. V.
Protasov, I. V.
author_sort Petrenko, O. V.
title Ultrafilters on \(G\)-spaces
title_short Ultrafilters on \(G\)-spaces
title_full Ultrafilters on \(G\)-spaces
title_fullStr Ultrafilters on \(G\)-spaces
title_full_unstemmed Ultrafilters on \(G\)-spaces
title_sort ultrafilters on \(g\)-spaces
description For a discrete group \(G\) and a discrete \(G\)-space \(X\), we identify the Stone-Cech compactifications \(\beta G\) and \(\beta X\) with the sets of all ultrafilters on \(G\) and \(X\), and apply the natural action of \(\beta G\) on \(\beta X\) to characterize large, thick, thin, sparse and scattered subsets of \(X\). We use \(G\)-invariant partitions and colorings to define \(G\)-selective and \(G\)-Ramsey ultrafilters on \(X\). We show that, in contrast to the set-theoretical case, these two classes of ultrafilters are distinct. We consider also universally thin ultrafilters on \(\omega\), the \(T\)-points, and study interrelations between these ultrafilters and some classical ultrafilters on \(\omega\).
publisher Lugansk National Taras Shevchenko University
publishDate 2015
url https://admjournal.luguniv.edu.ua/index.php/adm/article/view/69
work_keys_str_mv AT petrenkoov ultrafiltersongspaces
AT protasoviv ultrafiltersongspaces
first_indexed 2025-12-02T15:46:28Z
last_indexed 2025-12-02T15:46:28Z
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