English

Hanf numbers via accessible images

Logic 2023-06-22 v6 Category Theory

Abstract

We present several new model-theoretic applications of the fact that, under the assumption that there exists a proper class of almost strongly compact cardinals, the powerful image of any accessible functor is accessible. In particular, we generalize to the context of accessible categories the recent Hanf number computations of Baldwin and Boney, namely that in an abstract elementary class (AEC) if the joint embedding and amalgamation properties hold for models of size up to a sufficiently large cardinal, then they hold for models of arbitrary size. Moreover, we prove that, under the above-mentioned large cardinal assumption, every metric AEC is strongly d-tame, strengthening a result of Boney and Zambrano and pointing the way to further generalizations.

Keywords

Cite

@article{arxiv.1610.07816,
  title  = {Hanf numbers via accessible images},
  author = {Michael Lieberman and Jiri Rosicky},
  journal= {arXiv preprint arXiv:1610.07816},
  year   = {2023}
}

Comments

v1: 15 pages. v2: 13 pages, reformatted with minor edits. v3: 15 pages, title changed from "Bootstrapping structural properties, via accessible images," proofs expanded, definitions clarified in response to referees' feedback. v4: 15 pages, dedication added. v5: 15 pages, minor corrections, in press

R2 v1 2026-06-22T16:30:49.903Z