English

Sequential and distributive forcings without choice

Logic 2022-12-22 v2

Abstract

In the Zermelo--Fraenkel set theory with the Axiom of Choice a forcing notion is "κ\kappa-distributive" if and only if it is "κ\kappa-sequential". We show that without the Axiom of Choice this equivalence fails, even if we include a weak form of the Axiom of Choice, the Principle of Dependent Choice for κ\kappa. Still, the equivalence may still hold along with very strong failures of the Axiom of Choice, assuming the consistency of large cardinal axioms. We also prove that while a κ\kappa-distributive forcing notion may violate Dependent Choice, it must preserve the Axiom of Choice for families of size κ\kappa. On the other hand, a κ\kappa-sequential can violate the Axiom of Choice for countable families. We also provide a condition of "quasiproperness" which is sufficient for the preservation of Dependent Choice, and is also necessary if the forcing notion is sequential.

Keywords

Cite

@article{arxiv.2112.14103,
  title  = {Sequential and distributive forcings without choice},
  author = {Asaf Karagila and Jonathan Schilhan},
  journal= {arXiv preprint arXiv:2112.14103},
  year   = {2022}
}

Comments

12 pages; accepted version

R2 v1 2026-06-24T08:33:33.944Z