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OPTIMAL RESULTS ON RECOGNIZABILITY FOR INFINITE TIME REGISTER MACHINES

Published online by Cambridge University Press:  22 December 2015

MERLIN CARL
MERLIN CARL*
Affiliation:
FACHBEREICH MATHEMATIK UND STATISTIK UNIVERSITÄT KONSTANZ 78457 KONSTANZ GERMANYE-mail: merlin.carl@uni-konstanz.de
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Abstract

Exploring further the properties of ITRM-recognizable reals started in [1], we provide a detailed analysis of recognizable reals and their distribution in Gödels constructible universe L. In particular, we show that new unrecognizable reals are generated at every index $\gamma \, \ge \,\omega _\omega ^{CK}$. We give a machine-independent characterization of recognizability by proving that a real r is recognizable if and only if it is ${\Sigma _1}$-definable over ${L_{\omega _\omega ^{CK,\,r}}}$ and that $r\, \in \,{L_{\omega _\omega ^{CK,\,r}}}$ for every recognizable real r and show that either every or no r with $r\, \in \,{L_{\omega _\omega ^{CK,\,r}}}$ generated over an index stage ${L_\gamma }$ is recognizable. Finally, the techniques developed along the way allow us to prove that the halting number for ITRMs is recognizable and that the set of ITRM-computable reals is not ITRM-decidable.

Keywords

03D6503D6003Exx03E45Infinite Time ComputabilityGeneralized ComputabilityInfinite Time Register MachinesRecognizable Reals
Type
Articles
Information
The Journal of Symbolic Logic , Volume 80 , Issue 4 , December 2015 , pp. 1116 - 1130
Copyright
Copyright © The Association for Symbolic Logic 2015 

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