The set-theoretic Kaufmann-Clote question
Logic
2025-07-18 v2
Abstract
Let be the set theory obtained from by removing the collection scheme, restricting separation to -formulae and adding an axiom asserting that every set is contained in a transitive set. Let denote the restriction of the collection scheme to -formulae. In this paper we prove that for , if is a model of and is a -elementary end extension of that satisfies and that contains a new ordinal but no least new ordinal, then holds in . This result is used to show that for , the minimum model of has no -elementary end extension that satisfies , providing a negative answer to the generalisation of a question posed by Kaufmann.
Keywords
Cite
@article{arxiv.2507.01176,
title = {The set-theoretic Kaufmann-Clote question},
author = {Zachiri McKenzie},
journal= {arXiv preprint arXiv:2507.01176},
year = {2025}
}
Comments
15 pages