English

Coarse selectors of groups

Group Theory 2021-03-24 v2

Abstract

For a group GG, FG\mathcal{F}_G denotes the set of all non-empty finite subsets of GG. We extend the finitary coarse structure of GG from G×GG\times G to FG×FG\mathcal{F}_G\times \mathcal{F}_G and say that a macro-uniform mapping f:FGFGf: \mathcal{F}_G \rightarrow \mathcal{F}_G (resp. f:[G]2Gf: [G]^2 \rightarrow G) is a finitary selector (resp. 2-selector) of GG if f(A)Af(A)\in A for each AFGA\in \mathcal{F}_G (resp. A[G]2 A \in [G]^2 ). We prove that a group GG admits a finitary selector iff GG admits a 2-selector and iff GG is a finite extension of an infinite cyclic subgroup or GG is countable and locally finite. We use this result to characterize groups admitting linear orders compatible with finitary coarse structures.

Keywords

Cite

@article{arxiv.2102.03790,
  title  = {Coarse selectors of groups},
  author = {Igor Protasov},
  journal= {arXiv preprint arXiv:2102.03790},
  year   = {2021}
}

Comments

finitary coarse structure, Cayley graph, selector

R2 v1 2026-06-23T22:54:46.059Z