An ordinal analysis of stability
- Michael RathjenAffiliated withDepartment of Pure Mathematics, University of Leeds Email author
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This paper is the first in a series of three which culminates in an ordinal analysis of Π12-comprehension. On the set-theoretic side Π12-comprehension corresponds to Kripke-Platek set theory, KP, plus Σ1-separation. The strength of the latter theory is encapsulated in the fact that it proves the existence of ordinals π such that, for all β>π, π is β-stable, i.e. L π is a Σ1-elementary substructure of L β . The objective of this paper is to give an ordinal analysis of a scenario of not too complicated stability relations as experience has shown that the understanding of the ordinal analysis of Π12-comprehension is greatly facilitated by explicating certain simpler cases first.
This paper introduces an ordinal representation system based on ν-indescribable cardinals which is then employed for determining an upper bound for the proof–theoretic strength of the theory KPi+ ∀ρ ∃π π is π+ρ-stable, where KPi is KP augmented by the axiom saying that every set is contained in an admissible set.
- An ordinal analysis of stability
Archive for Mathematical Logic
Volume 44, Issue 1 , pp 1-62
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- Michael Rathjen (1)
- Author Affiliations
- 1. Department of Pure Mathematics, University of Leeds, Leeds, LS2 9JT, England