Constructing nonstandard hulls and Loeb measures in internal set theories
Logic
2023-01-03 v1 Classical Analysis and ODEs
Abstract
Currently the two popular ways to practice Robinson's nonstandard analysis are the model-theoretic approach and the axiomatic/syntactic approach. It is sometimes claimed that the internal axiomatic approach is unable to handle constructions relying on external sets. We show that internal frameworks provide successful accounts of nonstandard hulls and Loeb measures. The basic fact this work relies on is that the ultrapower of the standard universe by a standard ultrafilter is naturally isomorphic to a subuniverse of the internal universe.
Keywords
Cite
@article{arxiv.2301.00367,
title = {Constructing nonstandard hulls and Loeb measures in internal set theories},
author = {Karel Hrbacek and Mikhail G. Katz},
journal= {arXiv preprint arXiv:2301.00367},
year = {2023}
}
Comments
34 pages, to appear in Bulletin of Symbolic Logic