English

On the Cantor and Hilbert Cube Frames and the Alexandroff-Hausdorff Theorem

Category Theory 2021-02-08 v3 General Topology

Abstract

The aim of this work is to give a pointfree description of the Cantor set. It can be shown that the Cantor set is homeomorphic to the pp-adic integers Zp:={xQp:xp1}\mathbb{Z}_{p}:=\{x\in\mathbb{Q}_{p}: |x|_p\leq 1\} for every prime number pp. To give a pointfree description of the Cantor set, we specify the frame of Zp\mathbb{Z}_{p} by generators and relations. We use the fact that the open balls centered at integers generate the open subsets of Zp\mathbb{Z}_{p} and thus we think of them as the basic generators; on this poset we impose some relations and then the resulting quotient is the frame of the Cantor set L(Zp)\mathcal{L}(\mathbb{Z}_{p}). We prove that L(Zp)\mathcal{L}(\mathbb{Z}_{p}) is a spatial frame whose space of points is homeomorphic to Zp\mathbb{Z}_{p}. In particular, we show with pointfree arguments that L(Zp)\mathcal{L}(\mathbb{Z}_{p}) is 00-dimensional, (completely) regular, compact, and metrizable (it admits a countably generated uniformity). Finally, we give a point-free counterpart of the Hausdorff-Alexandroff Theorem which states that \emph{every compact metric space is a continuous image of the Cantor space} (see, e.g. \cite{Alexandroff} and \cite{Hausdorff}). We prove the point-free analog: if LL is a compact metrizable frame, then there is an injective frame homomorphism from LL into L(Z2)\mathcal{L}(\mathbb{Z}_{2}).

Keywords

Cite

@article{arxiv.2102.01794,
  title  = {On the Cantor and Hilbert Cube Frames and the Alexandroff-Hausdorff Theorem},
  author = {Francisco Ávila and Julio Urenda and Angel Zaldívar},
  journal= {arXiv preprint arXiv:2102.01794},
  year   = {2021}
}

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R2 v1 2026-06-23T22:47:02.346Z