English

Some new computable structures of high rank

Logic 2016-06-06 v1

Abstract

We give several new examples of computable structures of high Scott rank. For earlier known computable structures of Scott rank ω1CK\omega_1^{CK}, the computable infinitary theory is 0\aleph_0-categorical. Millar and Sacks asked whether this was always the case. We answer this question by constructing an example whose computable infinitary theory has non-isomorphic countable models. The standard known computable structures of Scott rank ω1CK+1\omega_1^{CK}+1 have infinite indiscernible sequences. We give two constructions with no indiscernible ordered triple.

Keywords

Cite

@article{arxiv.1606.00900,
  title  = {Some new computable structures of high rank},
  author = {Matthew Harrison-Trainor and Gregory Igusa and Julia F. Knight},
  journal= {arXiv preprint arXiv:1606.00900},
  year   = {2016}
}

Comments

12 pages

R2 v1 2026-06-22T14:16:25.968Z