Algebraic characterizations of some relative notions of size
Abstract
We obtain algebraic characterizations of relative notions of size in a discrete semigroup that generalize the usual combinatorial notions of syndetic, thick, and piecewise syndetic sets. "Filtered" syndetic and piecewise syndetic sets were defined and applied earlier by Shuungula, Zelenyuk, and Zelenyuk [24]. Other instances of these relative notions of size have appeared explicitly (and more often implicitly) in the literature related to the algebraic structure of the Stone-\v{C}ech compactification. Building on this prior work, we observe a natural duality and demonstrate how these notions of size may be composed to characterize previous notions of size (like piecewise syndetic sets) and serve as a convenient description for new notions of size.
Keywords
Cite
@article{arxiv.2105.09723,
title = {Algebraic characterizations of some relative notions of size},
author = {Cory Christopherson and John H. Johnson},
journal= {arXiv preprint arXiv:2105.09723},
year = {2021}
}
Comments
Final Version: 21 pages; numbered problem and question; incorporation of changes suggested by referee; correction of several more typos, improvements to expositions, and the addition of two more references (accepted to Semigroup Forum)