English

Many subalgebras of $\mathcal{P}(\omega)/\mathit{fin}$

General Topology 2026-04-07 v4 Logic

Abstract

In answer to a question on Mathoverflow we show that the Boolean algebra P(ω)/fin\mathcal{P}(\omega)/\mathit{fin} contains a family {BX:Xc}\{\mathcal{B}_X:X\subseteq\mathfrak{c}\} of subalgebras with the property that XYX\subseteq Y implies BY\mathcal{B}_Y is a subalgebra of BX\mathcal{B}_X and if X⊈YX\not\subseteq Y then BY\mathcal{B}_Y is not embeddable into~BX\mathcal{B}_X. The proof proceeds by Stone duality and the construction of a suitable family of separable zero-dimensional compact spaces.

Keywords

Cite

@article{arxiv.2303.08491,
  title  = {Many subalgebras of $\mathcal{P}(\omega)/\mathit{fin}$},
  author = {Klaas Pieter Hart},
  journal= {arXiv preprint arXiv:2303.08491},
  year   = {2026}
}

Comments

Version 2: added a description of a 40-years old answer to the original question Version 3: final version after referee's report; submitted to the journal. 2026-04-06: Fixed a few annoying typos