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MULTIDIMENSIONAL EXACT CLASSES, SMOOTH APPROXIMATION AND BOUNDED 4-TYPES

Part of: Model theory

Published online by Cambridge University Press:  07 September 2020

DANIEL WOLF
DANIEL WOLF*
Affiliation:
Formerly of the SCHOOL OF MATHEMATICS UNIVERSITY OF LEEDSLEEDS LS2 9JT, UKE-mail: dwolfeu@gmail.com
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Abstract

In connection with the work of Anscombe, Macpherson, Steinhorn and the present author in [1] we investigate the notion of a multidimensional exact class (R-mec), a special kind of multidimensional asymptotic class (R-mac) with measuring functions that yield the exact sizes of definable sets, not just approximations. We use results about smooth approximation [24] and Lie coordinatization [13] to prove the following result (Theorem 4.6.4), as conjectured by Macpherson: For any countable language $\mathcal {L}$ and any positive integer d the class $\mathcal {C}(\mathcal {L},d)$ of all finite $\mathcal {L}$-structures with at most d 4-types is a polynomial exact class in $\mathcal {L}$, where a polynomial exact class is a multidimensional exact class with polynomial measuring functions.

Keywords

asymptotic classsmooth approximationLie coordinatization

MSC classification

Primary: 03C13: Finite structures
Secondary: 03C20: Ultraproducts and related constructions
Type
Articles
Information
The Journal of Symbolic Logic , Volume 85 , Issue 4 , December 2020 , pp. 1305 - 1341
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Copyright
© The Association for Symbolic Logic 2020

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Footnotes

Dedicated to the memories of my son Arthur and my mother Valerie

References

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