English

Ramsey-like theorems and moduli of computation

Logic 2020-10-28 v1

Abstract

Ramsey's theorem asserts that every kk-coloring of [ω]n[\omega]^n admits an infinite monochromatic set. Whenever n3n \geq 3, there exists a computable kk-coloring of [ω]n[\omega]^n whose solutions compute the halting set. On the other hand, for every computable kk-coloring of [ω]2[\omega]^2 and every non-computable set CC, there is an infinite monochromatic set HH such that C̸THC \not \leq_T H. The latter property is known as cone avoidance. In this article, we design a natural class of Ramsey-like theorems encompassing many statements studied in reverse mathematics. We prove that this class admits a maximal statement satisfying cone avoidance and use it as a criterion to re-obtain many existing proofs of cone avoidance. This maximal statement asserts the existence, for every kk-coloring of [ω]n[\omega]^n, of an infinite subdomain HωH \subseteq \omega over which the coloring depends only on the sparsity of its elements. This confirms the intuition that Ramsey-like theorems compute Turing degrees only through the sparsity of its solutions.

Keywords

Cite

@article{arxiv.1901.04388,
  title  = {Ramsey-like theorems and moduli of computation},
  author = {Ludovic Patey},
  journal= {arXiv preprint arXiv:1901.04388},
  year   = {2020}
}

Comments

26 pages

R2 v1 2026-06-23T07:11:13.513Z