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Ramsey-type graph coloring and diagonal non-computability

Ramsey-type graph coloring and diagonal non-computability A function is diagonally non-computable (d.n.c.) if it diagonalizes against the universal partial computable function. D.n.c. functions play a central role in algorithmic randomness and reverse mathematics. Flood and Towsner asked for which functions h, the principle stating the existence of an h-bounded d.n.c. function (h-DNR) implies Ramsey-type weak König’s lemma (RWKL). In this paper, we prove that for every computable order h, there exists an $${\omega}$$ ω -model of h-DNR which is not a not model of the Ramsey-type graph coloring principle for two colors (RCOLOR 2) and therefore not a model of RWKL. The proof combines bushy tree forcing and a technique introduced by Lerman, Solomon and Towsner to transform a computable non-reducibility into a separation over $${\omega}$$ ω -models. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Archive for Mathematical Logic Springer Journals

Ramsey-type graph coloring and diagonal non-computability

Archive for Mathematical Logic , Volume 54 (8) – Sep 21, 2015

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References (25)

Publisher
Springer Journals
Copyright
Copyright © 2015 by Springer-Verlag Berlin Heidelberg
Subject
Mathematics; Mathematical Logic and Foundations; Mathematics, general; Algebra
ISSN
0933-5846
eISSN
1432-0665
DOI
10.1007/s00153-015-0448-5
Publisher site
See Article on Publisher Site

Abstract

A function is diagonally non-computable (d.n.c.) if it diagonalizes against the universal partial computable function. D.n.c. functions play a central role in algorithmic randomness and reverse mathematics. Flood and Towsner asked for which functions h, the principle stating the existence of an h-bounded d.n.c. function (h-DNR) implies Ramsey-type weak König’s lemma (RWKL). In this paper, we prove that for every computable order h, there exists an $${\omega}$$ ω -model of h-DNR which is not a not model of the Ramsey-type graph coloring principle for two colors (RCOLOR 2) and therefore not a model of RWKL. The proof combines bushy tree forcing and a technique introduced by Lerman, Solomon and Towsner to transform a computable non-reducibility into a separation over $${\omega}$$ ω -models.

Journal

Archive for Mathematical LogicSpringer Journals

Published: Sep 21, 2015

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