[PDF][PDF] Some set-theoretic reduction principles

M Bärtschi, G Jäger - Peter Schroeder-Heister on Proof-Theoretic …, 2024 - library.oapen.org
In this article we study several reduction principles in the context of Simpson's set theory
ATR𝑆 0 and Kripke-Platek set theory KP (with infinity). Since ATR𝑆 0 is the set-theoretic …

[HTML][HTML] Admissible extensions of subtheories of second order arithmetic

G Jäger, M Rathjen - Annals of Pure and Applied Logic, 2024 - Elsevier
In this paper we study admissible extensions of several theories T of reverse mathematics.
The idea is that in such an extension the structure M=(N, S,∈) of the natural numbers and …