English

On algebraic sums, trees and ideals in the Baire space

General Topology 2024-09-27 v1

Abstract

We work in the Baire space Zω\mathbb{Z}^\omega equipped with the coordinate-wise addition ++. Consider a σ\sigma-ideal I\mathcal{I} and a family T\mathbb{T} of some kind of perfect trees. We are interested in results of the form: for every AIA\in \mathcal{I} and a tree TTT\in\mathbb{T} there exists TT,TTT'\in \mathbb{T}, T'\subseteq T such that A+[T]+[T]++[T]n–timesIA+\underbrace{[T']+[T']+\dots +[T']}_{\text{n--times}}\in \mathcal{I} for each nωn\in\omega. Explored tree types include perfect trees, uniformly perfect trees, Miller trees, Laver trees and ω\omega-Silver trees. The latter kind of trees is an analogue of Silver trees from the Cantor space. Besides the standard σ\sigma-ideal M\mathcal{M} of meager sets, we also analyze M\mathcal{M}_- and fake null sets N\mathcal{N}. The latter two are born out of the characterizations of their respective analogues in the Cantor space. The key ingredient in proofs were combinatorial characterizations of these ideals in the Baire space.

Keywords

Cite

@article{arxiv.2409.17748,
  title  = {On algebraic sums, trees and ideals in the Baire space},
  author = {Łukasz Mazurkiewicz and Marcin Michalski and Robert Rałowski and Szymon Żeberski},
  journal= {arXiv preprint arXiv:2409.17748},
  year   = {2024}
}