English

Scott-Karp analysis without sentences

Logic 2026-02-10 v1

Abstract

Scott and Karp gave an analysis which provides a level-by-level equivalence between global similarity between two structures and local commonality in terms of sharing particular invariants. Scott and Karp's local invariants were certain infinitary formulae. We give a more abstract version of the local side of Scott-Karp analysis which avoids the use of infinitary languages. We show the resulting hierarchies are still provide desired equivalences in the classical setting. Moreover, the abstract nature of our analysis, as we show, makes it suitable to provide local level-by-level equivalents to Hjorth's much more general version of global similarity in the context of topological group actions on topological groups. We, furthermore, provide, analogously to the classical work of Ehrenfeucht and Fra\"iss\'e, novel game theoretic equivalents for Hjorth's global similarity relations and some natural variants.

Keywords

Cite

@article{arxiv.2602.07646,
  title  = {Scott-Karp analysis without sentences},
  author = {Andreas Brunner and Charles Morgan and Darllan Concieção Pinto},
  journal= {arXiv preprint arXiv:2602.07646},
  year   = {2026}
}

Comments

23 pages

R2 v1 2026-07-01T10:26:09.746Z