Maximal sets without choice

We show that it is consistent relative to ZF , that there is no well-ordering of R while a wide class of special sets of reals such as Hamel bases, transcendence bases, Vitali sets or Bernstein sets exists. To be more precise, we can assume that every projective hypergraph on R has a maximal independent set, among a few other things. For example, we get transversals for all projective equivalence relations. Moreover, this is possible while either DC ω 1 holds, or countable choice for reals fails. Assuming the consistency of an inaccessible cardinal, “projective” can even be replaced with “ L ( R ) ” and we can add that any instance of AC in L ( R ) has a choice function. This vastly strengthens the consistency results obtained in [6] , [11] or [15] .

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Publication Details

Journal
Annals of Pure and Applied Logic
Published
2025-11-27
DOI
https://doi.org/10.1016/j.apal.2025.103694
Primary Topic
Advanced Topology and Set Theory
Type
article
Field-Weighted Citation Impact
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article

Maximal sets without choice

Jonathan Schilhan
Annals of Pure and Applied Logic
Advanced Topology and Set Theory
article

Maximal sets without choice

Jonathan Schilhan
article en

Abstract

We show that it is consistent relative to ZF , that there is no well-ordering of R while a wide class of special sets of reals such as Hamel bases, transcendence bases, Vitali sets or Bernstein sets exists. To be more precise, we can assume that every projective hypergraph on R has a maximal independent set, among a few other things. For example, we get transversals for all projective equivalence relations. Moreover, this is possible while either DC ω 1 holds, or countable choice for reals fails. Assuming the consistency of an inaccessible cardinal, “projective” can even be replaced with “ L ( R ) ” and we can add that any instance of AC in L ( R ) has a choice function. This vastly strengthens the consistency results obtained in [6] , [11] or [15] .

Annals of Pure and Applied LogicVol. 177(4)
University of Vienna (AT)
Openalex Percentile: Top 58%
Advanced Topology and Set Theory
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