English

Ramsey expansions of $\Lambda$-ultrametric spaces

Logic 2025-11-21 v1 Combinatorics

Abstract

For a finite lattice Λ\Lambda, Λ\Lambda-ultrametric spaces are a convenient language for describing structures equipped with a family of equivalence relations. When Λ\Lambda is finite and distributive, there exists a generic Λ\Lambda-ultrametric space, and we here identify a family of Ramsey expansions for that space. This then allows a description the universal minimal flow of its automorphism group, and also implies the Ramsey property for all known homogeneous finite-dimensional permutation structures, i.e. structures in a language of finitely many linear orders. A point of technical interest is that our proof involves classes with non-unary algebraic closure operations. As a byproduct of some of the concepts developed, we also arrive at a natural description of the known homogeneous finite-dimensional permutation structures, completing our previously begun "census".

Keywords

Cite

@article{arxiv.1710.01193,
  title  = {Ramsey expansions of $\Lambda$-ultrametric spaces},
  author = {Samuel Braunfeld},
  journal= {arXiv preprint arXiv:1710.01193},
  year   = {2025}
}
R2 v1 2026-06-22T22:02:29.580Z