English

On the first Banach problem, concerning condensations of absolute $\kappa$-Borel sets onto compacta

General Topology 2024-02-23 v6

Abstract

It is consistent that the continuum be arbitrary large and no absolute κ\kappa-Borel set XX of density κ\kappa, 1<κ<c\aleph_1<\kappa<\mathfrak{c}, condenses onto a compact metric space. It is consistent that the continuum be arbitrary large and any absolute κ\kappa-Borel set XX of density κ\kappa, κc\kappa\leq\mathfrak{c}, containing a closed subspace of the Baire space of weight κ\kappa, condenses onto a compactum. In particular, applying Brian's results in model theory, we get the following unexpected result. Given any ANA\subseteq \mathbb{N} with 1A1\in A, there is a forcing extension in which every absolute n\aleph_n-Borel set, containing a closed subspace of the Baire space of weight n\aleph_n, condenses onto a compactum if, and only if, nAn\in A.

Keywords

Cite

@article{arxiv.2209.05942,
  title  = {On the first Banach problem, concerning condensations of absolute $\kappa$-Borel sets onto compacta},
  author = {Alexander V. Osipov},
  journal= {arXiv preprint arXiv:2209.05942},
  year   = {2024}
}

Comments

6 pages