Ramsey expansions of $\Lambda$-ultrametric spaces
Abstract
For a finite lattice , -ultrametric spaces are a convenient language for describing structures equipped with a family of equivalence relations. When is finite and distributive, there exists a generic -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".
Cite
@article{arxiv.1710.01193,
title = {Ramsey expansions of $\Lambda$-ultrametric spaces},
author = {Samuel Braunfeld},
journal= {arXiv preprint arXiv:1710.01193},
year = {2025}
}