English

A strong failure of aleph_0-stability for atomic classes

Logic 2017-01-20 v1

Abstract

We study classes of atomic models At_T of a countable, complete first-order theory T . We prove that if At_T is not pcl-small, i.e., there is an atomic model N that realizes uncountably many types over pcl(a) for some finite tuple a from N, then there are 2^aleph1 non-isomorphic atomic models of T, each of size aleph1.

Keywords

Cite

@article{arxiv.1701.05474,
  title  = {A strong failure of aleph_0-stability for atomic classes},
  author = {Michael C. Laskowski and Saharon Shelah},
  journal= {arXiv preprint arXiv:1701.05474},
  year   = {2017}
}
R2 v1 2026-06-22T17:54:18.632Z