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Nichtbeweisbarkeit von gewissen kombinatorischen Eigenschaften endlicher Bäume

Nichtbeweisbarkeit von gewissen kombinatorischen Eigenschaften endlicher Bäume In this paper we exposit some as yet unpublished results of Harvey Friedman. These results provide the most dramatic examples so far known of mathematically meaningful theorems of finite combinatorics which are unprovable in certain logical systems. The relevant logical systems,ATR 0 and Π 1 1 —CA 0, are well known as relatively strong fragments of second order arithmetic. The unprovable combinatorial theorems are concerned with embeddability properties of finite trees. Friedman's method is based in part of the existence of a close relationship between finite trees on the one hand, and systems of ordinal notations which occur in Gentzen-style proof theory on the other. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Archive for Mathematical Logic Springer Journals

Nichtbeweisbarkeit von gewissen kombinatorischen Eigenschaften endlicher Bäume

Archive for Mathematical Logic , Volume 25 (1) – Jul 13, 2005

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References (33)

Publisher
Springer Journals
Copyright
Copyright © 1985 by Verlag W. Kohlhammer
Subject
Mathematics; Mathematical Logic and Foundations; Mathematics, general; Algebra
ISSN
0933-5846
eISSN
1432-0665
DOI
10.1007/BF02007556
Publisher site
See Article on Publisher Site

Abstract

In this paper we exposit some as yet unpublished results of Harvey Friedman. These results provide the most dramatic examples so far known of mathematically meaningful theorems of finite combinatorics which are unprovable in certain logical systems. The relevant logical systems,ATR 0 and Π 1 1 —CA 0, are well known as relatively strong fragments of second order arithmetic. The unprovable combinatorial theorems are concerned with embeddability properties of finite trees. Friedman's method is based in part of the existence of a close relationship between finite trees on the one hand, and systems of ordinal notations which occur in Gentzen-style proof theory on the other.

Journal

Archive for Mathematical LogicSpringer Journals

Published: Jul 13, 2005

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