English

Most(?) theories have Borel complete reducts

Logic 2021-09-21 v2

Abstract

We prove that many seemingly simple theories have Borel complete reducts. Specifically, if a countable theory has uncountably many complete 1-types, then it has a Borel complete reduct. Similarly, if Th(M)Th(M) is not small, then MeqM^{eq} has a Borel complete reduct, and if a theory TT is not ω\omega-stable, then the elementary diagram of some countable model of TT has a Borel complete reduct.

Keywords

Cite

@article{arxiv.2103.09724,
  title  = {Most(?) theories have Borel complete reducts},
  author = {Michael C. Laskowski and Douglas S. Ulrich},
  journal= {arXiv preprint arXiv:2103.09724},
  year   = {2021}
}

Comments

Accepted version, will appear in Journal of Symbolic Logic. Typos fixed

R2 v1 2026-06-24T00:16:45.890Z