English

Does $\mathsf{DC}$ imply $\mathsf{AC}_\omega$, uniformly?

Logic 2025-01-07 v2

Abstract

The Axiom of Dependent Choice DC\mathsf{DC} and the Axiom of Countable Choice ACω\mathsf{AC}_\omega are two weak forms of the Axiom of Choice that can be stated for a specific set: DC(X)\mathsf{DC}(X) asserts that any total binary relation on XX has an infinite chain, while ACω(X)\mathsf{AC}_\omega (X) asserts that any countable collection of nonempty subsets of XX has a choice function. It is well-known that DCACω\mathsf{DC} \Rightarrow \mathsf{AC}_\omega. We study for which sets and under which hypotheses DC(X)ACω(X)\mathsf{DC}(X) \Rightarrow \mathsf{AC}_\omega (X), and then we show it is consistent with ZF\mathsf{ZF} that there is a set ARA \subseteq \mathbb{R} for which DC(A)\mathsf{DC} (A) holds, but ACω(A)\mathsf{AC}_\omega (A) fails.

Cite

@article{arxiv.2305.06676,
  title  = {Does $\mathsf{DC}$ imply $\mathsf{AC}_\omega$, uniformly?},
  author = {Alessandro Andretta and Lorenzo Notaro},
  journal= {arXiv preprint arXiv:2305.06676},
  year   = {2025}
}

Comments

23 pages

R2 v1 2026-06-28T10:31:51.105Z