English

Forbidden cycles in metrically homogeneous graphs

Combinatorics 2025-11-03 v3 Discrete Mathematics Logic

Abstract

In a recent paper by a superset of the authors it was proved that for every primitive 3-constrained space Γ\Gamma of finite diameter δ\delta from Cherlin's catalogue of metrically homogeneous graphs, there exists a finite family F\mathcal F of {1,,δ}\{1,\ldots, \delta\}-edge-labelled cycles such that a {1,,δ}\{1,\ldots, \delta\}-edge-labelled graph is a subgraph of Γ\Gamma if and only if it contains no homomorphic images of cycles from F\mathcal F. However, the cycles in the families F\mathcal F were not described explicitly as it was not necessary for the analysis of Ramsey expansions and the extension property for partial automorphisms. This paper fills this gap by providing an explicit description of the cycles in the families F\mathcal F, heavily using the previous result in the process. Additionally, we explore the potential applications of this result, such as interpreting the graphs as semigroup-valued metric spaces or homogenizations of ω\omega-categorical {1,δ}\{1,\delta\}-edge-labelled graphs.

Keywords

Cite

@article{arxiv.1808.05177,
  title  = {Forbidden cycles in metrically homogeneous graphs},
  author = {Jan Hubička and Michael Kompatscher and Matěj Konečný},
  journal= {arXiv preprint arXiv:1808.05177},
  year   = {2025}
}

Comments

25 pages. Updated references, journal version now in print in European Journal of Combinatorics

R2 v1 2026-06-23T03:34:51.113Z