Documentation

LeanPool.PointwiseComposition.Foundation.FirstOrder.Incompleteness.Definability

Supporting results for pointwise provable equality.

Definability of arithmetical syntax #

This file constructs internal recognizers for arithmetical syntax and recursively enumerable presentations of 𝐏𝐀 and 𝐈Σ₁.

Internal iterated universal quantifier qqAlls #

The blueprint construction in FFL.FirstOrder.Arithmetic.Bootstrapping.qqAlls.

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    The construction construction in FFL.FirstOrder.Arithmetic.Bootstrapping.qqAlls.

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      The qq Alls Def construction in FFL.FirstOrder.Arithmetic.

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        castLE-invariance of the Gödel code and free variables #

        The bv-pin bridge #

        Pins the number of leading universals m recognized by the induction-scheme code to fvSup χ.

        Internal free-variable vector fvarVec #

        The blueprint construction in FFL.FirstOrder.Arithmetic.Bootstrapping.fvarVec.

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          The construction construction in FFL.FirstOrder.Arithmetic.Bootstrapping.fvarVec.

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            Σ₁ side condition: internal IsSigma1 predicate (for C = Hierarchy Σ 1) #

            qqBall u q = ^∀ ((^#0 ^≮ u) ^⋎ q), the code of ∀¹[“#0 < u”] q.

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              The qq Ball Def construction in FFL.FirstOrder.Arithmetic.

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                Single-step operator: p is Σ₁ given that its immediate subformulas in C are.

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                  The blueprint construction in FFL.FirstOrder.Arithmetic.Bootstrapping.IsSigma1F.

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                    The construction construction in FFL.FirstOrder.Arithmetic.Bootstrapping.IsSigma1F.

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                      theorem PointwiseComposition.FFL.FirstOrder.Arithmetic.Bootstrapping.IsSigma1.case_iff {V : Type u_1} [ORingStructure V] [V↓[ℒₒᵣ] ⊧* 𝐈Σ₁] {p : V} :
                      IsSigma1 p ↔ p = qqVerum ∨ p = qqFalsum ∨ (∃ (k : V) (r : V) (v : V), p = qqRel k r v) ∨ (∃ (k : V) (r : V) (v : V), p = qqNRel k r v) ∨ (∃ (p₁ : V) (p₂ : V), IsSigma1 p₁ ∧ IsSigma1 p₂ ∧ p = qqAnd p₁ p₂) ∨ (∃ (p₁ : V) (p₂ : V), IsSigma1 p₁ ∧ IsSigma1 p₂ ∧ p = qqOr p₁ p₂) ∨ (∃ (p₁ : V), IsSigma1 p₁ ∧ p = qqExs p₁) ∨ ∃ (u : V) (q : V), (∃ (t : V), IsUTerm ℒₒᵣ t ∧ u = termBShift ℒₒᵣ t) ∧ IsSigma1 q ∧ p = qqBall u q
                      theorem PointwiseComposition.FFL.FirstOrder.Arithmetic.Bootstrapping.IsSigma1.mk {V : Type u_1} [ORingStructure V] [V↓[ℒₒᵣ] ⊧* 𝐈Σ₁] {p : V} :
                      (p = qqVerum ∨ p = qqFalsum ∨ (∃ (k : V) (r : V) (v : V), p = qqRel k r v) ∨ (∃ (k : V) (r : V) (v : V), p = qqNRel k r v) ∨ (∃ (p₁ : V) (p₂ : V), IsSigma1 p₁ ∧ IsSigma1 p₂ ∧ p = qqAnd p₁ p₂) ∨ (∃ (p₁ : V) (p₂ : V), IsSigma1 p₁ ∧ IsSigma1 p₂ ∧ p = qqOr p₁ p₂) ∨ (∃ (p₁ : V), IsSigma1 p₁ ∧ p = qqExs p₁) ∨ ∃ (u : V) (q : V), (∃ (t : V), IsUTerm ℒₒᵣ t ∧ u = termBShift ℒₒᵣ t) ∧ IsSigma1 q ∧ p = qqBall u q) → IsSigma1 p

                      Alias of the reverse direction of PointwiseComposition.FFL.FirstOrder.Arithmetic.Bootstrapping.IsSigma1.case_iff.

                      theorem PointwiseComposition.FFL.FirstOrder.Arithmetic.Bootstrapping.IsSigma1.case {V : Type u_1} [ORingStructure V] [V↓[ℒₒᵣ] ⊧* 𝐈Σ₁] {p : V} :
                      IsSigma1 p → p = qqVerum ∨ p = qqFalsum ∨ (∃ (k : V) (r : V) (v : V), p = qqRel k r v) ∨ (∃ (k : V) (r : V) (v : V), p = qqNRel k r v) ∨ (∃ (p₁ : V) (p₂ : V), IsSigma1 p₁ ∧ IsSigma1 p₂ ∧ p = qqAnd p₁ p₂) ∨ (∃ (p₁ : V) (p₂ : V), IsSigma1 p₁ ∧ IsSigma1 p₂ ∧ p = qqOr p₁ p₂) ∨ (∃ (p₁ : V), IsSigma1 p₁ ∧ p = qqExs p₁) ∨ ∃ (u : V) (q : V), (∃ (t : V), IsUTerm ℒₒᵣ t ∧ u = termBShift ℒₒᵣ t) ∧ IsSigma1 q ∧ p = qqBall u q

                      Alias of the forward direction of PointwiseComposition.FFL.FirstOrder.Arithmetic.Bootstrapping.IsSigma1.case_iff.

                      𝐏𝐀⁻ is Δ₁ #

                      Typed decomposition of succInd #

                      The typed succInd shape as a function of the (typed) core code K = ⌜ψ⌝.

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                        The raw V → V form of (indBody ·).val.

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                          A concrete Σ₁-graph for indBodyVal #

                          Standard ℕ-code of the substitution vector ![⌜‘0’⌝] (the ψ(0) instance).

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                            Standard ℕ-code of the substitution vector ![⌜‘#0+1’⌝] (the ψ(x+1) instance).

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                              Concrete Σ₁-graph of indBodyVal, a chain of the subst/imp/qqAll graphs.

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                                The induction schema is Δ₁ #

                                The recognizer predicate for InductionScheme ℒₒᵣ C over a model V, parameterized by a side condition S on the recovered core.

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                                  Concrete ∆₁.Semisentence 1 recognizer for InductionR cond.

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                                    A freevar-free, bv-pinned formula β that substitutes back to succInd γ is exactly the fixitr-image, so its m-fold closure equals (succInd γ).univCl'.

                                    InductionR S fires exactly on codes of universal closures of succInd ψ for ψ with C ψ, given that S correctly recognizes the codes of C-formulas.

                                    @[instance_reducible]

                                    The induction schema InductionScheme ℒₒᵣ Set.univ is Δ₁, via the recognizer chUniv.

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                                    Correctness of IsSigma1: IsSigma1 ⌜ψ⌝ ↔ Hierarchy Σ 1 ψ #

                                    @[instance_reducible]

                                    The induction schema InductionScheme ℒₒᵣ (Hierarchy Σ 1) is Δ₁, via chSigma1.

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                                    𝐏𝐀 and 𝐈Σ₁ are recursively enumerable #

                                    𝐏𝐀 and 𝐈Σ₁ are Δ₁ #

                                    TODO: remove. Not mathematically essential — RE above already suffices.

                                    @[instance_reducible]
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