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MODEL THEORETIC STABILITY AND DEFINABILITY OF TYPES, AFTER A. GROTHENDIECK

Published online by Cambridge University Press:  30 December 2014

ITAÏ BEN YAACOV*
Affiliation:
UNIVERSITÉ CLAUDE BERNARD – LYON 1, INSTITUT CAMILLE JORDAN, CNRS UMR 5208, 43 BOULEVARD DU 11 NOVEMBRE 1918, 69622 VILLEURBANNE CEDEX, FRANCE URL: http://math.univ-lyon1.fr/∼begnac/

Abstract

We point out how the “Fundamental Theorem of Stability Theory”, namely the equivalence between the “non order property” and definability of types, proved by Shelah in the 1970s, is in fact an immediate consequence of Grothendieck’s “Critères de compacité” from 1952. The familiar forms for the defining formulae then follow using Mazur’s Lemma regarding weak convergence in Banach spaces.

Type
Articles
Copyright
Copyright © The Association for Symbolic Logic 2014 

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References

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