English

Owings-like theorems for infinitely many colours or finite monochromatic sets

Logic 2024-07-24 v4 Combinatorics

Abstract

Inspired by Owings's problem, we investigate whether, for a given an Abelian group GG and cardinal numbers κ,θ\kappa,\theta, every colouring c:Gθc:G\longrightarrow\theta yields a subset XGX\subseteq G with X=κ|X|=\kappa such that X+XX+X is monochromatic. (Owings's problem asks this for G=ZG=\mathbb Z, θ=2\theta=2 and κ=0\kappa=\aleph_0; this is known to be false for the same GG and κ\kappa but θ=3\theta=3.) We completely settle the question for κ\kappa and θ\theta both finite (by obtaining sufficient and necessary conditions for a positive answer) and for κ\kappa and θ\theta both infinite (with a negative answer). Also, in the case where θ\theta is infinite but κ\kappa is finite, we obtain some sufficient conditions for a negative answer as well as an example with a positive answer.

Keywords

Cite

@article{arxiv.2402.13124,
  title  = {Owings-like theorems for infinitely many colours or finite monochromatic sets},
  author = {David J. Fernández-Bretón and Eliseo Sarmiento Rosales and Germán Vera},
  journal= {arXiv preprint arXiv:2402.13124},
  year   = {2024}
}

Comments

14 pages. Some proofs (especially in Section 2) omit various details at the request of the referee; to see more detailed proofs the reader should refer to v2