Ordinal de Feferman-Schütte
- Ordinal de Feferman-Schütte
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En mathématiques, et plus précisément en théorie des ensembles, l’ordinal de Feferman–Schütte, noté Γ0, est un grand ordinal dénombrable, étudié par Solomon Feferman (en) et Kurt Schütte (en).
Définition
L'ordinal de Feferman–Schütte est le plus petit ordinal qui ne peut être atteint à partir de 0 en utilisant seulement l'addition des ordinaux et les fonctions de Veblen (en) φα(β).Autrement dit, c'est le plus petit α tel que φα(0) = α.
Propriétés
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Références
- (en) Wolfram Pohlers, Proof theory, vol. 1407, Berlin, Springer-Verlag, 1989 (ISBN 3-540-51842-8)
- (en) Nik Weaver, Predicativity beyond Gamma_0, 2005
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