PreprintCC BY 4.0arXiv
Vopěnka's Principle without Choice: Preservation under Symmetric Extensions
Abstract
We give a detailed proof that every set-sized symmetric extension of a model of ZF+VP again satisfies ZF+VP, where VP is formulated for arbitrary set-sized languages. For each standard n≥ 1, the same preservation theorem holds for VP(Πn), with set parameters and arbitrary set-sized languages. We also prove that ZF+VP and ZFC+VP are equiconsistent, and that ZF+VP proves the existence of a proper class of Löwenheim-Skolem cardinals. Relative to Con(ZF+VP), the axiom DC is independent of ZF+VP+¬AC. The preservation theorem also yields Feferman-Lévy and full Solovay models satisfying VP. We consider whether every countable model of ZF+VP has a class-generic extension satisfying ZFC+VP.
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BibTeX
@misc{groot2026vopěnkas,
title = {{Vopěnka's Principle without Choice: Preservation under Symmetric Extensions}},
author = {Tom de Groot and Wojciech Aleksander Wołoszyn},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2609.06856},
eprint = {2609.06856},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.06856},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Vopěnka's Principle without Choice: Preservation under Symmetric Extensions
AU - Tom de Groot
AU - Wojciech Aleksander Wołoszyn
PY - 2026
DA - 2026/10/08
PB - arXiv
DO - 10.48550/arxiv.2609.06856
UR - https://arxiv.org/abs/2609.06856
AB - We give a detailed proof that every set-sized symmetric extension of a model of ZF+VP again satisfies ZF+VP, where VP is formulated for arbitrary set-sized languages. For each standard n≥ 1, the same preservation theorem holds for VP(Π_n), with set parameters and arbitrary set-sized languages. We also prove that ZF+VP and ZFC+VP are equiconsistent, and that ZF+VP proves the existence of a proper class of Löwenheim-Skolem cardinals. Relative to Con(ZF+VP), the axiom DC is independent of ZF+VP+¬AC. The preservation theorem also yields Feferman-Lévy and full Solovay models satisfying VP. We consider whether every countable model of ZF+VP has a class-generic extension satisfying ZFC+VP.
ER -