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STRONG REDUCTIONS BETWEEN COMBINATORIAL PRINCIPLES

Published online by Cambridge University Press:  01 December 2016

DAMIR D. DZHAFAROV
DAMIR D. DZHAFAROV*
Affiliation:
DEPARTMENT OF MATHEMATICS UNIVERSITY OF CONNECTICUT 196 AUDITORIUM ROAD STORRS, CT06269, USA E-mail: damir@math.uconn.edu
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Abstract

This paper is a contribution to the growing investigation of strong reducibilities between ${\rm{\Pi }}_2^1$ statements of second-order arithmetic, viewed as an extension of the traditional analysis of reverse mathematics. We answer several questions of Hirschfeldt and Jockusch [13] about Weihrauch (uniform) and strong computable reductions between various combinatorial principles related to Ramsey’s theorem for pairs. Among other results, we establish that the principle $SRT_2^2$ is not Weihrauch or strongly computably reducible to $D_{ < \infty }^2$, and that COH is not Weihrauch reducible to $SRT_{ < \infty }^2$, or strongly computably reducible to $SRT_2^2$. The last result also extends a prior result of Dzhafarov [9]. We introduce a number of new techniques for controlling the combinatorial and computability-theoretic properties of the problems and solutions we construct in our arguments.

Keywords

Ramsey’s theoremreverse mathematicscomputability theoryWeihrauch reducibilitycomputable reducibility
Type
Articles
Information
The Journal of Symbolic Logic , Volume 81 , Issue 4 , December 2016 , pp. 1405 - 1431
Copyright
Copyright © The Association for Symbolic Logic 2016 

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