Balleans and G-spaces
We show that every ballean (equivalently, coarse structure) on a set X can be determined by some group G of permutations of X and some group ideal I on G. We refine this characterization for some basic classes of balleans (metrizable, cellular, graph, locally finite, and uniformly locally finite). T...
Збережено в:
| Дата: | 2012 |
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| Автори: | , |
| Формат: | Стаття |
| Мова: | English |
| Опубліковано: |
Інститут математики НАН України
2012
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| Назва видання: | Український математичний журнал |
| Теми: | |
| Онлайн доступ: | http://dspace.nbuv.gov.ua/handle/123456789/164148 |
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| Назва журналу: | Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| Цитувати: | Balleans and G-spaces / O.V. Petrenko, I.V. Protasov // Український математичний журнал. — 2012. — Т. 64, № 3. — С. 344-350. — Бібліогр.: 7 назв. — англ. |
Репозитарії
Digital Library of Periodicals of National Academy of Sciences of Ukraine| Резюме: | We show that every ballean (equivalently, coarse structure) on a set X can be determined by some group G of permutations of X and some group ideal I on G. We refine this characterization for some basic classes of balleans (metrizable, cellular, graph, locally finite, and uniformly locally finite). Then we show that a free ultrafilter U on ω is a T -point with respect to the class of all metrizable locally finite balleans on ω if and only if U is a Q-point. The paper is concluded with a list of open questions. |
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