English

Nearly all known Euclidean Ramsey sets are subsoluble

Combinatorics 2025-12-05 v3

Abstract

A finite set XX in a Euclidean space Rd\mathbb{R}^d is called Ramsey if for every kk there exists an integer nn such that whenever Rn\mathbb{R}^n is coloured with kk colours, there is a monochromatic copy of XX. Graham conjectured that all spherical sets are Ramsey, but progress on this conjecture has been slow. A key result of K\v{r}\'{i}\v{z} is that all sets that embed in sets that are acted on transitively by a soluble group are Ramsey. We show that for nearly all known examples of Ramsey sets the converse is true, with only two possible exceptions.

Keywords

Cite

@article{arxiv.2510.15677,
  title  = {Nearly all known Euclidean Ramsey sets are subsoluble},
  author = {Natalie Behague},
  journal= {arXiv preprint arXiv:2510.15677},
  year   = {2025}
}

Comments

15 pages, 2 figures. Version 2: Replaced proof that simplices are subsoluble with citation for pre-existing proof by Karamanlis. Version 3: Corrected some minor errors and added Figure 3