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A proof of strongly uniform termination for Gödel's $T$ by methods from local predicativity

A proof of strongly uniform termination for Gödel's $T$ by methods from local predicativity We estimate the derivation lengths of functionals in Gödel's system $T$ of primitive recursive functionals of finite type by a purely recursion-theoretic analysis of Schütte's 1977 exposition of Howard's weak normalization proof for $T$ . By using collapsing techniques from Pohlers' local predicativity approach to proof theory and based on the Buchholz-Cichon and Weiermann 1994 approach to subrecursive hierarchies we define a collapsing f unction ${\cal D}:T\to \omega$ so that for (closed) terms $a,b$ of Gödel's $T$ we have: If $a$ reduces to $b$ then $\omega>{\cal D}(a)>{\cal D}(b).$ By one uniform proof we obtain as corollaries: A derivation lengths classification for functionals in $T$ , hence new proof of strongly uniform termination of $T$ . A new proof of the Kreisel's classific ation of the number-theoretic functions which can be defined in $T$ , hence a classification of the provably total functions of Peano Arithmetic. A new proof of Tait's results on weak normalization for $T$ . A new proof of Troelstra's result on strong normalization for $T$ . Additionally, a slow growing analysis of Gödel's $T$ is obtained via Girard's hierarchy comparison theorem. This analyis yields a contribution to two open pro blems posed by Girard in part two of his book on proof theory. For the sake of completeness we also mention the Howard Schütte bound on derivation lengths for the simple typed $\lambda$ -calculus. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Archive for Mathematical Logic Springer Journals

A proof of strongly uniform termination for Gödel's $T$ by methods from local predicativity

Archive for Mathematical Logic , Volume 36 (6) – Oct 1, 1997

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References (39)

Publisher
Springer Journals
Copyright
Copyright © 1997 by Springer-Verlag Berlin Heidelberg
Subject
Mathematics; Mathematical Logic and Foundations; Mathematics, general; Algebra
ISSN
0933-5846
eISSN
1432-0665
DOI
10.1007/s001530050075
Publisher site
See Article on Publisher Site

Abstract

We estimate the derivation lengths of functionals in Gödel's system $T$ of primitive recursive functionals of finite type by a purely recursion-theoretic analysis of Schütte's 1977 exposition of Howard's weak normalization proof for $T$ . By using collapsing techniques from Pohlers' local predicativity approach to proof theory and based on the Buchholz-Cichon and Weiermann 1994 approach to subrecursive hierarchies we define a collapsing f unction ${\cal D}:T\to \omega$ so that for (closed) terms $a,b$ of Gödel's $T$ we have: If $a$ reduces to $b$ then $\omega>{\cal D}(a)>{\cal D}(b).$ By one uniform proof we obtain as corollaries: A derivation lengths classification for functionals in $T$ , hence new proof of strongly uniform termination of $T$ . A new proof of the Kreisel's classific ation of the number-theoretic functions which can be defined in $T$ , hence a classification of the provably total functions of Peano Arithmetic. A new proof of Tait's results on weak normalization for $T$ . A new proof of Troelstra's result on strong normalization for $T$ . Additionally, a slow growing analysis of Gödel's $T$ is obtained via Girard's hierarchy comparison theorem. This analyis yields a contribution to two open pro blems posed by Girard in part two of his book on proof theory. For the sake of completeness we also mention the Howard Schütte bound on derivation lengths for the simple typed $\lambda$ -calculus.

Journal

Archive for Mathematical LogicSpringer Journals

Published: Oct 1, 1997

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