An independence result for \((\Pi^ 1_ 1-CA)+BI\) (Q1097882)
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scientific article; zbMATH DE number 4035824
| Language | Label | Description | Also known as |
|---|---|---|---|
| English | An independence result for \((\Pi^ 1_ 1-CA)+BI\) |
scientific article; zbMATH DE number 4035824 |
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An independence result for \((\Pi^ 1_ 1-CA)+BI\) (English)
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1987
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This paper meets a combinatorial problem by modern means of proof theory, which can be clothed in the legend of Hercules and the Hydra: A hydr AB This paper meets a combinatorial problem by modern means of proof theory, which can be clothed in the legend of Hercules and the Hydra: A hydra is a finite tree, each node of which is labelled by some element of the set \(\{+\} \cup (\omega + 1)\). Cutting a head ( = leaf of the tree) of the hydra is defined in such a way that from stroke to stroke the beast seems to increase. But surprisingly, it can be proven.
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proof theory
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Hercules
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Hydra
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finite tree
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wellfounded trees
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