Characterizing $ (\mathcal{F}, \mathcal{G}) $-syndetic, $ (\mathcal{F}, \mathcal{G}) $-thick, and related notions of size using derived sets along ultrafilters

Fuente: arXiv
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Main Authors: Burns, Shea D., Davenport, Dennis, Frankson, Shakuan, Griffin, Conner, Johnson Jr., John H., Kebe, Malick
Format: Preprint
Published: 2025
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_version_ 1866914200945688576
author Burns, Shea D.
Davenport, Dennis
Frankson, Shakuan
Griffin, Conner
Johnson Jr., John H.
Kebe, Malick
author_facet Burns, Shea D.
Davenport, Dennis
Frankson, Shakuan
Griffin, Conner
Johnson Jr., John H.
Kebe, Malick
contents We characterize relative notions of syndetic and thick sets using, what we call, "derived" sets along ultrafilters. Manipulations of derived sets is a characteristic feature of algebra in the Stone-Čech compactification and its applications. Combined with the existence of idempotents and structure of the smallest ideal in closed subsemigroups of the Stone-Čch compactification, our particular use of derived sets adapt and generalize methods recently used by Griffin arXiv:2311.09436 to characterize relative piecewise syndetic sets. As an application, we define an algebraically interesting subset of the Stone-Čech compactification and show, in some ways, it shares structural properties analogous to the smallest ideal.
format Preprint
id arxiv_https___arxiv_org_abs_2503_05579
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Characterizing $ (\mathcal{F}, \mathcal{G}) $-syndetic, $ (\mathcal{F}, \mathcal{G}) $-thick, and related notions of size using derived sets along ultrafilters
Burns, Shea D.
Davenport, Dennis
Frankson, Shakuan
Griffin, Conner
Johnson Jr., John H.
Kebe, Malick
General Topology
54D35, 54D80 (Primary) 22A15 (Secondary)
We characterize relative notions of syndetic and thick sets using, what we call, "derived" sets along ultrafilters. Manipulations of derived sets is a characteristic feature of algebra in the Stone-Čech compactification and its applications. Combined with the existence of idempotents and structure of the smallest ideal in closed subsemigroups of the Stone-Čch compactification, our particular use of derived sets adapt and generalize methods recently used by Griffin arXiv:2311.09436 to characterize relative piecewise syndetic sets. As an application, we define an algebraically interesting subset of the Stone-Čech compactification and show, in some ways, it shares structural properties analogous to the smallest ideal.
title Characterizing $ (\mathcal{F}, \mathcal{G}) $-syndetic, $ (\mathcal{F}, \mathcal{G}) $-thick, and related notions of size using derived sets along ultrafilters
topic General Topology
54D35, 54D80 (Primary) 22A15 (Secondary)
url https://arxiv.org/abs/2503.05579