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Use DerivabilityCondition for simple proof #4

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merged 1 commit into from
Sep 3, 2024

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SnO2WMaN
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素人考えではLogic.FirstOrder.Incompleteness.DerivabilityConditionを使えば証明はほとんど削減できるのではと思うのだが、どうなのだろうか?一応Diagonalizaation, D1, D2, D3は通っているので、GoedelSound(特にゲーデル文に対しての健全性)だけあとは証明できれば第二不完全性定理およびLoebの定理が直ちに従うはず。

追伸: ArithmetizationのリポジトリにブランチをpushしてPRを作る権限がないので渡してもらえると若干助かる。

@@ -133,6 +146,7 @@ lemma provableₐ_D2_context {Γ σ π} (hσπ : Γ ⊢[T]! U.bewₐ (σ ⟶ π)

lemma provableₐ_D3_context {Γ σ} (hσπ : Γ ⊢[T]! U.bewₐ σ) : Γ ⊢[T]! U.bewₐ (U.bewₐ σ) := of'! provableₐ_D3 ⨀ hσπ

instance : U.provₐ.GoedelSound T U := ⟨by sorry⟩
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これさえ証明が通れば残りは直ちに従う。競合を防ぐため自分はこのPRに今後触れないので、適当に書き直してマージするなりどうぞ。

@iehality
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もちろんそうなのだけれど,現状GoedelSound T Uを示すのに手こずっており,またprovableₐは特別な証明可導述語だから個別に示しておきたいと思った(mathlibでNat.PrimePrimeが別に定義されているように).

@iehality iehality merged commit a723da5 into FormalizedFormalLogic:master Sep 3, 2024
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@SnO2WMaN SnO2WMaN deleted the dc branch September 4, 2024 01:12
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2 participants