English

Lineability of functions in $C(K)$ with specified range

Functional Analysis 2024-01-19 v2

Abstract

This paper is inspired by the paper of Leonetti, Russo and Somaglia [\textit{Dense lineability and spaceability in certain subsets of \ell_\infty.} Bull. London Math. Soc., 55: 2283--2303 (2023)] and the lineability problems raised therein. It concerns the properties of \ell_\infty subsets defined by cluster points of sequences. Using the fact that the set of cluster points of a sequence xx depends only on its equivalence class in /c0\ell_\infty/c_0 and that the quotient space /c0\ell_\infty/c_0 is isometrically isomorphic to C(βNN)C(\beta\mathbb{N}\setminus\mathbb{N}), we are able to translate lineability problems from \ell_\infty to C(βNN)C(\beta\mathbb{N}\setminus\mathbb{N}). We prove that for a compact space KK with properties similar to those of βNN\beta\mathbb{N}\setminus\mathbb{N}, the sets of continuous functions ff in C(K)C(K) with rng(f)=ω\vert\operatorname{rng}(f)\vert=\omega and those ff with rng(f)=c\vert\operatorname{rng}(f)\vert=\mathfrak c contain, up to zero function, an isometric copy of c0(κ)c_0(\kappa) for uncountable cardinal κ\kappa. Specializing those results to some closed subspaces KK of βNN\beta\mathbb{N}\setminus\mathbb{N} we are able to generalize known results to their ideal versions.

Keywords

Cite

@article{arxiv.2311.11414,
  title  = {Lineability of functions in $C(K)$ with specified range},
  author = {Artur Bartoszewicz and Szymon Głcab},
  journal= {arXiv preprint arXiv:2311.11414},
  year   = {2024}
}
R2 v1 2026-06-28T13:25:31.661Z