Mathematically strong subsystems of analysis with low rate of growth of provably recursive functionals
Mathematically strong subsystems of analysis with low rate of growth of provably recursive functionals
复制标题
数学上强大的分析子系统,可证明递归泛函的增长率较低
DOI:
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发表时间:
1996
影响因子:
0.3
通讯作者:
U. Kohlenbach
中科院分区:
文献类型:
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作者:
U. Kohlenbach
This paper is the first one in a sequel of papers resulting from the authors Habilitationsschrift [22] which are devoted to determine the growth in proofs of standard parts of analysis. A hierarchy (GnA )n∈IN of systems of arithmetic in all finite types is introduced whose definable objects of type 1 = 0(0) correspond to the Grzegorczyk hierarchy of primitive recursive functions. We establish the following extraction rule for an extension of GnA ω by quantifier–free choice AC–qf and analytical axioms Γ having the form ∀x∃y ≤ρ sx∀z F0 (including also a ‘non– standard’ axiom F which does not hold in the full set–theoretic model but in the strongly majorizable functionals): From a proof GnA +AC–qf + Γ ⊢ ∀u, k∀v ≤τ tuk∃w A0(u, k, v, w) one can extract a uniform bound Φ such that ∀u, k∀v ≤τ tuk∃w ≤ ΦukA0(u, k, v, w) holds in the full set–theoretic type structure. In case n = 2 (resp. n = 3) Φuk is a polynomial (resp. an elementary recursive function) in k, u := λx.max(u0, . . . , ux). In the present paper we show that for n ≥ 2, GnA +AC–qf+F proves a generalization of the binary Konig’s lemma yielding new conservation results since the conclusion of the above rule can be verified in Gmax(3,n)A ω in this case. In a subsequent paper we will show that many important ineffective analytical principles and theorems can be proved already in G2A +AC–qf+Γ for suitable Γ.