Relatively thin and sparse subsets of groups

• Published in: Український математичний журнал
• Date: 2011
• Main Authors: Lutsenko, Ie., Protasov, I.V.
• Format: Article
• Language: English
• Published: Інститут математики НАН України 2011
• Subjects: Статті
• Online Access: https://nasplib.isofts.kiev.ua/handle/123456789/166348
• Journal Title: Digital Library of Periodicals of National Academy of Sciences of Ukraine
• Cite this: Relatively thin and sparse subsets of groups / Ie. Lutsenko, I.V. Protasov // Український математичний журнал. — 2011. — Т. 63, № 2. — С. 216–225. — Бібліогр.: 7 назв. — англ.

Let G be a group with identity e and let I be a left-invariant ideal in the Boolean algebra PG of all subsets of G. A subset A of G is called I-thin if gA⋂A∈I for every g∈G {e}. A subset A of G is called I-sparse if, for every infinite subset S of G, there exists a finite subset F⊂S such that ⋂g∈FgA...