Sequential and distributive forcings without choice
Abstract
In the Zermelo--Fraenkel set theory with the Axiom of Choice a forcing notion is "-distributive" if and only if it is "-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 . 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 -distributive forcing notion may violate Dependent Choice, it must preserve the Axiom of Choice for families of size . On the other hand, a -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