Equivalence of bar induction and bar recursion for continuous functions with continuous moduli
Equivalence of bar induction and bar recursion for continuous functions with continuous moduli
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对于具有连续模的连续函数,条形归纳和条形递归等价
DOI:
10.1016/j.apal.2019.04.001
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发表时间:
2019
影响因子:
0.8
通讯作者:
Makoto Fujiwara and Tatsuji Kawai
中科院分区:
文献类型:
--
作者:
Makoto Fujiwara and Tatsuji Kawai
We compare Brouwer's bar theorem and Spector's bar recursion for the lowest type in the context of constructive reverse mathematics. To this end, we reformulate bar recursion as a logical principle stating the existence of a bar recursor for every function which serves as the stopping condition of bar recursion. We then show that the decidable bar induction is equivalent to the existence of a bar recursor for every continuous function from N N to N with a continuous modulus. We also introduce fan recursion, the bar recursion for binary trees, and show that the decidable fan theorem is equivalent to the existence of a fan recursor for every continuous function from {0, 1} N to N with a continuous modulus. The equivalence for bar induction holds over the extensional version of intuitionistic arithmetic in all finite types augmented with the characteristic principles of Gödel's Dialectica interpretation. On the other hand, we show the equivalence for fan theorem without using such extra principles.