Ramsey-like theorems and moduli of computation
Abstract
Ramsey's theorem asserts that every -coloring of admits an infinite monochromatic set. Whenever , there exists a computable -coloring of whose solutions compute the halting set. On the other hand, for every computable -coloring of and every non-computable set , there is an infinite monochromatic set such that . 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 -coloring of , of an infinite subdomain 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.
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