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THE STRUCTURAL COMPLEXITY OF MODELS OF ARITHMETIC

Part of: Nonstandard models Model theory Set theory

Published online by Cambridge University Press:  29 June 2023

ANTONIO MONTALBÁN  and
DINO ROSSEGGER Open the ORCID record for DINO ROSSEGGER [Opens in a new window]
ANTONIO MONTALBÁN
Affiliation:
DEPARTMENT OF MATHEMATICS UNIVERSITY OF CALIFORNIA, BERKELEY BERKELEY, CA, USA E-mail: antonio@math.berkeley.edu
DINO ROSSEGGER*
Affiliation:
DEPARTMENT OF MATHEMATICS UNIVERSITY OF CALIFORNIA, BERKELEY BERKELEY, CA, USA INSTITUTE OF DISCRETE MATHEMATICS AND GEOMETRY TECHNISCHE UNIVERSITÄT WIEN VIENNA, AUSTRIA
*
E-mail: dino@math.berkeley.edu
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Abstract

We calculate the possible Scott ranks of countable models of Peano arithmetic. We show that no non-standard model can have Scott rank less than $\omega $ and that non-standard models of true arithmetic must have Scott rank greater than $\omega $. Other than that there are no restrictions. By giving a reduction via $\Delta ^{\mathrm {in}}_{1}$ bi-interpretability from the class of linear orderings to the canonical structural $\omega $-jump of models of an arbitrary completion T of $\mathrm {PA}$ we show that every countable ordinal $\alpha>\omega $ is realized as the Scott rank of a model of T.

Keywords

arithmeticScott rankPeano arithmeticnonstandard models

MSC classification

Primary: 03E15: Descriptive set theory 03C62: Models of arithmetic and set theory 03H15: Nonstandard models of arithmetic
Type
Article
Information
The Journal of Symbolic Logic , First View , pp. 1 - 17
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Copyright
© The Author(s), 2023. Published by Cambridge University Press on behalf of The Association for Symbolic Logic

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