205 lines
7.5 KiB
Text
205 lines
7.5 KiB
Text
/-
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Copyright (c) 2024 Joseph Tooby-Smith. All rights reserved.
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Released under Apache 2.0 license as described in the file LICENSE.
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Authors: Joseph Tooby-Smith
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-/
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import HepLean.PerturbationTheory.Wick.CreateAnnilateSection
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import HepLean.PerturbationTheory.Wick.KoszulOrder
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/-!
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# Koszul signs and ordering for lists and algebras
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-/
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namespace Wick
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open HepLean.List
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open FieldStatistic
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noncomputable section
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variable {𝓕 : Type} (q : 𝓕 → FieldStatistic) (le : 𝓕 → 𝓕 → Prop) [DecidableRel le]
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/-- The element of the free algebra `FreeAlgebra ℂ I` associated with a `List I`. -/
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def ofList (l : List 𝓕) (x : ℂ) : FreeAlgebra ℂ 𝓕 :=
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FreeAlgebra.equivMonoidAlgebraFreeMonoid.symm (MonoidAlgebra.single l x)
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lemma ofList_pair (l r : List 𝓕) (x y : ℂ) :
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ofList (l ++ r) (x * y) = ofList l x * ofList r y := by
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simp only [ofList, ← map_mul, MonoidAlgebra.single_mul_single, EmbeddingLike.apply_eq_iff_eq]
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rfl
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lemma ofList_triple (la lb lc : List 𝓕) (xa xb xc : ℂ) :
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ofList (la ++ lb ++ lc) (xa * xb * xc) = ofList la xa * ofList lb xb * ofList lc xc := by
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rw [ofList_pair, ofList_pair]
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lemma ofList_triple_assoc (la lb lc : List 𝓕) (xa xb xc : ℂ) :
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ofList (la ++ (lb ++ lc)) (xa * (xb * xc)) = ofList la xa * ofList lb xb * ofList lc xc := by
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rw [ofList_pair, ofList_pair]
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exact Eq.symm (mul_assoc (ofList la xa) (ofList lb xb) (ofList lc xc))
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lemma ofList_cons_eq_ofList (l : List 𝓕) (i : 𝓕) (x : ℂ) :
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ofList (i :: l) x = ofList [i] 1 * ofList l x := by
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simp only [ofList, ← map_mul, MonoidAlgebra.single_mul_single, one_mul,
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EmbeddingLike.apply_eq_iff_eq]
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rfl
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lemma ofList_singleton (i : 𝓕) :
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ofList [i] 1 = FreeAlgebra.ι ℂ i := by
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simp only [ofList, FreeAlgebra.equivMonoidAlgebraFreeMonoid, MonoidAlgebra.of_apply,
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MonoidAlgebra.single, AlgEquiv.ofAlgHom_symm_apply, MonoidAlgebra.lift_single, one_smul]
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rfl
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lemma ofList_eq_smul_one (l : List 𝓕) (x : ℂ) :
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ofList l x = x • ofList l 1 := by
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simp only [ofList]
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rw [← map_smul]
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simp
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lemma ofList_empty : ofList [] 1 = (1 : FreeAlgebra ℂ 𝓕) := by
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simp only [ofList, EmbeddingLike.map_eq_one_iff]
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rfl
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lemma ofList_empty' : ofList [] x = x • (1 : FreeAlgebra ℂ 𝓕) := by
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rw [ofList_eq_smul_one, ofList_empty]
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lemma koszulOrder_ofList
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(l : List 𝓕) (x : ℂ) :
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koszulOrder q le (ofList l x) = (koszulSign q le l) • ofList (List.insertionSort le l) x := by
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rw [ofList]
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rw [koszulOrder_single]
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change ofList (List.insertionSort le l) _ = _
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rw [ofList_eq_smul_one]
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conv_rhs => rw [ofList_eq_smul_one]
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rw [smul_smul]
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lemma ofList_insertionSort_eq_koszulOrder (l : List 𝓕) (x : ℂ) :
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ofList (List.insertionSort le l) x = (koszulSign q le l) • koszulOrder q le (ofList l x) := by
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rw [koszulOrder_ofList]
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rw [smul_smul]
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rw [koszulSign_mul_self]
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simp
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/-- The map of algebras from `FreeAlgebra ℂ I` to `FreeAlgebra ℂ (Σ i, f i)` taking
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the monomial `i` to the sum of elements in `(Σ i, f i)` above `i`, i.e. the sum of the fiber
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above `i`. -/
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def sumFiber (f : 𝓕 → Type) [∀ i, Fintype (f i)] :
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FreeAlgebra ℂ 𝓕 →ₐ[ℂ] FreeAlgebra ℂ (Σ i, f i) :=
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FreeAlgebra.lift ℂ fun i => ∑ (j : f i), FreeAlgebra.ι ℂ ⟨i, j⟩
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lemma sumFiber_ι (f : 𝓕 → Type) [∀ i, Fintype (f i)] (i : 𝓕) :
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sumFiber f (FreeAlgebra.ι ℂ i) = ∑ (b : f i), FreeAlgebra.ι ℂ ⟨i, b⟩ := by
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simp [sumFiber]
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/-- Given a list `l : List I` the corresponding element of `FreeAlgebra ℂ (Σ i, f i)`
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by mapping each `i : I` to the sum of it's fiber in `Σ i, f i` and taking the product of the
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result.
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For example, in terms of creation and annihlation opperators,
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`[φ₁, φ₂, φ₃]` gets taken to `(φ₁⁰ + φ₁¹)(φ₂⁰ + φ₂¹)(φ₃⁰ + φ₃¹)`.
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-/
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def ofListLift (f : 𝓕 → Type) [∀ i, Fintype (f i)] (l : List 𝓕) (x : ℂ) :
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FreeAlgebra ℂ (Σ i, f i) :=
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sumFiber f (ofList l x)
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lemma ofListLift_empty (f : 𝓕 → Type) [∀ i, Fintype (f i)] :
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ofListLift f [] 1 = 1 := by
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simp only [ofListLift, EmbeddingLike.map_eq_one_iff]
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rw [ofList_empty]
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exact map_one (sumFiber f)
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lemma ofListLift_empty_smul (f : 𝓕 → Type) [∀ i, Fintype (f i)] (x : ℂ) :
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ofListLift f [] x = x • 1 := by
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simp only [ofListLift, EmbeddingLike.map_eq_one_iff]
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rw [ofList_eq_smul_one]
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rw [ofList_empty]
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simp
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lemma ofListLift_cons (f : 𝓕 → Type) [∀ i, Fintype (f i)] (i : 𝓕) (r : List 𝓕) (x : ℂ) :
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ofListLift f (i :: r) x = (∑ j : f i, FreeAlgebra.ι ℂ ⟨i, j⟩) * (ofListLift f r x) := by
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rw [ofListLift, ofList_cons_eq_ofList, ofList_singleton, map_mul]
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conv_lhs => lhs; rw [sumFiber]
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rw [ofListLift]
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simp
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lemma ofListLift_singleton (f : 𝓕 → Type) [∀ i, Fintype (f i)] (i : 𝓕) (x : ℂ) :
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ofListLift f [i] x = ∑ j : f i, x • FreeAlgebra.ι ℂ ⟨i, j⟩ := by
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simp only [ofListLift]
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rw [ofList_eq_smul_one, ofList_singleton, map_smul]
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rw [sumFiber_ι]
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rw [Finset.smul_sum]
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lemma ofListLift_singleton_one (f : 𝓕 → Type) [∀ i, Fintype (f i)] (i : 𝓕) :
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ofListLift f [i] 1 = ∑ j : f i, FreeAlgebra.ι ℂ ⟨i, j⟩ := by
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simp only [ofListLift]
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rw [ofList_eq_smul_one, ofList_singleton, map_smul]
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rw [sumFiber_ι]
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rw [Finset.smul_sum]
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simp
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lemma ofListLift_cons_eq_ofListLift (f : 𝓕 → Type) [∀ i, Fintype (f i)] (i : 𝓕)
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(r : List 𝓕) (x : ℂ) :
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ofListLift f (i :: r) x = ofListLift f [i] 1 * ofListLift f r x := by
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rw [ofListLift_cons, ofListLift_singleton]
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simp only [one_smul]
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lemma ofListLift_expand (f : 𝓕 → Type) [∀ i, Fintype (f i)] (x : ℂ) :
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(l : List 𝓕) → ofListLift f l x = ∑ (a : CreateAnnilateSect f l), ofList a.toList x
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| [] => by
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simp only [ofListLift, CreateAnnilateSect, List.length_nil, List.get_eq_getElem,
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Finset.univ_unique, CreateAnnilateSect.toList, Finset.sum_const, Finset.card_singleton,
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one_smul]
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rw [ofList_eq_smul_one, map_smul, ofList_empty, ofList_eq_smul_one, ofList_empty, map_one]
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| i :: l => by
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rw [ofListLift_cons, ofListLift_expand f x l]
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conv_rhs => rw [← (CreateAnnilateSect.extractEquiv
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⟨0, by exact Nat.zero_lt_succ l.length⟩).symm.sum_comp (α := FreeAlgebra ℂ _)]
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erw [Finset.sum_product]
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rw [Finset.sum_mul]
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conv_lhs =>
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rhs
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intro n
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rw [Finset.mul_sum]
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congr
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funext j
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congr
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funext n
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rw [← ofList_singleton, ← ofList_pair, one_mul]
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rfl
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lemma koszulOrder_ofListLift {f : 𝓕 → Type} [∀ i, Fintype (f i)]
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(l : List 𝓕) (x : ℂ) :
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koszulOrder (fun i => q i.fst) (fun i j => le i.1 j.1) (ofListLift f l x) =
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sumFiber f (koszulOrder q le (ofList l x)) := by
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rw [koszulOrder_ofList]
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rw [map_smul]
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change _ = _ • ofListLift _ _ _
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rw [ofListLift_expand]
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rw [map_sum]
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conv_lhs =>
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rhs
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intro a
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rw [koszulOrder_ofList]
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rw [CreateAnnilateSect.toList_koszulSign]
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rw [← Finset.smul_sum]
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apply congrArg
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conv_lhs =>
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rhs
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intro n
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rw [← CreateAnnilateSect.sort_toList]
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rw [ofListLift_expand]
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refine Fintype.sum_equiv
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((HepLean.List.insertionSortEquiv le l).piCongr fun i => Equiv.cast ?_) _ _ ?_
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congr 1
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· rw [← HepLean.List.insertionSortEquiv_get]
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simp
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· intro x
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rfl
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lemma koszulOrder_ofListLift_eq_ofListLift {f : 𝓕 → Type} [∀ i, Fintype (f i)]
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(l : List 𝓕) (x : ℂ) : koszulOrder (fun i => q i.fst) (fun i j => le i.1 j.1)
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(ofListLift f l x) =
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koszulSign q le l • ofListLift f (List.insertionSort le l) x := by
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rw [koszulOrder_ofListLift, koszulOrder_ofList, map_smul]
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rfl
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end
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end Wick
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