English

The Strength of Some Combinatorial Principles Related to Ramsey's Theorem for Pairs

Logic 2014-08-14 v1

Abstract

We study the reverse mathematics and computability-the\-o\-re\-tic strength of (stable) Ramsey's Theorem for pairs and the related principles COH and DNR. We show that SRT22^2_2 implies DNR over RCA0_0 but COH does not, and answer a question of Mileti by showing that every computable stable 22-coloring of pairs has an incomplete Δ20\Delta^0_2 infinite homogeneous set. We also give some extensions of the latter result, and relate it to potential approaches to showing that SRT22^2_2 does not imply RT22^2_2.

Keywords

Cite

@article{arxiv.1408.2897,
  title  = {The Strength of Some Combinatorial Principles Related to Ramsey's Theorem for Pairs},
  author = {Denis R. Hirschfeldt and Carl G. Jockusch and Bjørn Kjos-Hanssen and Steffen Lempp and Theodore A. Slaman},
  journal= {arXiv preprint arXiv:1408.2897},
  year   = {2014}
}