179 lines
7.5 KiB
Text
179 lines
7.5 KiB
Text
/-
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Copyright (c) 2025 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.WickContraction.Sign.Basic
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import HepLean.PerturbationTheory.FieldOpAlgebra.TimeContraction
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/-!
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# Time contractions
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-/
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open FieldSpecification
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variable {𝓕 : FieldSpecification}
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namespace WickContraction
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variable {n : ℕ} (c : WickContraction n)
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open HepLean.List
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open FieldOpAlgebra
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/-- Given a Wick contraction `φsΛ` associated with a list `φs`, the
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product of all time-contractions of pairs of contracted elements in `φs`,
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as a member of the center of `𝓞.A`. -/
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noncomputable def timeContract {φs : List 𝓕.FieldOp}
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(φsΛ : WickContraction φs.length) :
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Subalgebra.center ℂ 𝓕.FieldOpAlgebra :=
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∏ (a : φsΛ.1), ⟨FieldOpAlgebra.timeContract
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(φs.get (φsΛ.fstFieldOfContract a)) (φs.get (φsΛ.sndFieldOfContract a)),
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timeContract_mem_center _ _⟩
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/-- For `φsΛ` a Wick contraction for `φs`, the time contraction `(φsΛ ↩Λ φ i none).timeContract 𝓞`
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is equal to `φsΛ.timeContract 𝓞`.
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This result follows from the fact that `timeContract` only depends on contracted pairs,
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and `(φsΛ ↩Λ φ i none)` has the 'same' contracted pairs as `φsΛ`. -/
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@[simp]
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lemma timeContract_insertAndContract_none (φ : 𝓕.FieldOp) (φs : List 𝓕.FieldOp)
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(φsΛ : WickContraction φs.length) (i : Fin φs.length.succ) :
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(φsΛ ↩Λ φ i none).timeContract = φsΛ.timeContract := by
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rw [timeContract, insertAndContract_none_prod_contractions]
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congr
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ext a
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simp
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/-- For `φsΛ` a Wick contraction for `φs = φ₀…φₙ`, the time contraction
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`(φsΛ ↩Λ φ i (some j)).timeContract 𝓞` is equal to the multiple of
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- the time contraction of `φ` with `φⱼ` if `i < i.succAbove j` else
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`φⱼ` with `φ`.
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- `φsΛ.timeContract 𝓞`.
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This follows from the fact that `(φsΛ ↩Λ φ i (some j))` has one more contracted pair than `φsΛ`,
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corresponding to `φ` contracted with `φⱼ`. The order depends on whether we insert `φ` before
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or after `φⱼ`. -/
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lemma timeContract_insertAndContract_some
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(φ : 𝓕.FieldOp) (φs : List 𝓕.FieldOp)
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(φsΛ : WickContraction φs.length) (i : Fin φs.length.succ) (j : φsΛ.uncontracted) :
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(φsΛ ↩Λ φ i (some j)).timeContract =
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(if i < i.succAbove j then
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⟨FieldOpAlgebra.timeContract φ φs[j.1], timeContract_mem_center _ _⟩
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else ⟨FieldOpAlgebra.timeContract φs[j.1] φ, timeContract_mem_center _ _⟩) *
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φsΛ.timeContract := by
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rw [timeContract, insertAndContract_some_prod_contractions]
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congr 1
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· simp only [Nat.succ_eq_add_one, insertAndContract_fstFieldOfContract_some_incl, finCongr_apply,
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List.get_eq_getElem, insertAndContract_sndFieldOfContract_some_incl, Fin.getElem_fin]
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split
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· simp
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· simp
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· congr
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ext a
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simp
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@[simp]
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lemma timeContract_empty (φs : List 𝓕.FieldOp) :
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(@empty φs.length).timeContract = 1 := by
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rw [timeContract, empty]
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simp
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open FieldStatistic
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lemma timeContract_insertAndContract_some_eq_mul_contractStateAtIndex_lt
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(φ : 𝓕.FieldOp) (φs : List 𝓕.FieldOp)
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(φsΛ : WickContraction φs.length) (i : Fin φs.length.succ) (k : φsΛ.uncontracted)
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(ht : 𝓕.timeOrderRel φ φs[k.1]) (hik : i < i.succAbove k) :
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(φsΛ ↩Λ φ i (some k)).timeContract =
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𝓢(𝓕 |>ₛ φ, 𝓕 |>ₛ ⟨φs.get, (φsΛ.uncontracted.filter (fun x => x < k))⟩)
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• (contractStateAtIndex φ [φsΛ]ᵘᶜ ((uncontractedFieldOpEquiv φs φsΛ) (some k)) *
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φsΛ.timeContract) := by
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rw [timeContract_insertAndContract_some]
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simp only [Nat.succ_eq_add_one, Fin.getElem_fin, ite_mul, instCommGroup.eq_1,
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contractStateAtIndex, uncontractedFieldOpEquiv, Equiv.optionCongr_apply,
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Equiv.coe_trans, Option.map_some', Function.comp_apply, finCongr_apply, Fin.coe_cast,
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List.getElem_map, uncontractedList_getElem_uncontractedIndexEquiv_symm, List.get_eq_getElem,
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Algebra.smul_mul_assoc, uncontractedListGet]
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· simp only [hik, ↓reduceIte, MulMemClass.coe_mul]
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rw [timeContract_of_timeOrderRel]
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trans (1 : ℂ) • ((superCommute (anPart φ)) (ofFieldOp φs[k.1]) * ↑φsΛ.timeContract)
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· simp
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simp only [smul_smul]
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congr 1
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have h1 : ofList 𝓕.statesStatistic (List.take (↑(φsΛ.uncontractedIndexEquiv.symm k))
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(List.map φs.get φsΛ.uncontractedList))
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= (𝓕 |>ₛ ⟨φs.get, (Finset.filter (fun x => x < k) φsΛ.uncontracted)⟩) := by
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simp only [ofFinset]
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congr
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rw [← List.map_take]
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congr
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rw [take_uncontractedIndexEquiv_symm]
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rw [filter_uncontractedList]
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rw [h1]
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simp only [exchangeSign_mul_self]
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· exact ht
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lemma timeContract_insertAndContract_some_eq_mul_contractStateAtIndex_not_lt
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(φ : 𝓕.FieldOp) (φs : List 𝓕.FieldOp)
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(φsΛ : WickContraction φs.length) (i : Fin φs.length.succ) (k : φsΛ.uncontracted)
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(ht : ¬ 𝓕.timeOrderRel φs[k.1] φ) (hik : ¬ i < i.succAbove k) :
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(φsΛ ↩Λ φ i (some k)).timeContract =
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𝓢(𝓕 |>ₛ φ, 𝓕 |>ₛ ⟨φs.get, (φsΛ.uncontracted.filter (fun x => x ≤ k))⟩)
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• (contractStateAtIndex φ [φsΛ]ᵘᶜ
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((uncontractedFieldOpEquiv φs φsΛ) (some k)) * φsΛ.timeContract) := by
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rw [timeContract_insertAndContract_some]
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simp only [Nat.succ_eq_add_one, Fin.getElem_fin, ite_mul, instCommGroup.eq_1,
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contractStateAtIndex, uncontractedFieldOpEquiv, Equiv.optionCongr_apply,
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Equiv.coe_trans, Option.map_some', Function.comp_apply, finCongr_apply, Fin.coe_cast,
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List.getElem_map, uncontractedList_getElem_uncontractedIndexEquiv_symm, List.get_eq_getElem,
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Algebra.smul_mul_assoc, uncontractedListGet]
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simp only [hik, ↓reduceIte, MulMemClass.coe_mul]
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rw [timeContract_of_not_timeOrderRel, timeContract_of_timeOrderRel]
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simp only [instCommGroup.eq_1, Algebra.smul_mul_assoc, smul_smul]
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congr
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have h1 : ofList 𝓕.statesStatistic (List.take (↑(φsΛ.uncontractedIndexEquiv.symm k))
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(List.map φs.get φsΛ.uncontractedList))
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= (𝓕 |>ₛ ⟨φs.get, (Finset.filter (fun x => x < k) φsΛ.uncontracted)⟩) := by
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simp only [ofFinset]
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congr
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rw [← List.map_take]
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congr
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rw [take_uncontractedIndexEquiv_symm, filter_uncontractedList]
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rw [h1]
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trans 𝓢(𝓕 |>ₛ φ, 𝓕 |>ₛ ⟨φs.get, {k.1}⟩)
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· rw [exchangeSign_symm, ofFinset_singleton]
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simp
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rw [← map_mul]
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congr
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rw [ofFinset_union]
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congr
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ext a
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simp only [Finset.mem_singleton, Finset.mem_sdiff, Finset.mem_union, Finset.mem_filter,
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Finset.mem_inter, not_and, not_lt, and_imp]
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apply Iff.intro
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· intro h
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subst h
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simp
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· intro h
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have h1 := h.1
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rcases h1 with h1 | h1
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· have h2' := h.2 h1.1 h1.2 h1.1
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omega
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· have h2' := h.2 h1.1 (by omega) h1.1
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omega
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have ht := IsTotal.total (r := timeOrderRel) φs[k.1] φ
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simp_all only [Fin.getElem_fin, Nat.succ_eq_add_one, not_lt, false_or]
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exact ht
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lemma timeContract_of_not_gradingCompliant (φs : List 𝓕.FieldOp)
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(φsΛ : WickContraction φs.length) (h : ¬ GradingCompliant φs φsΛ) :
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φsΛ.timeContract = 0 := by
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rw [timeContract]
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simp only [GradingCompliant, Fin.getElem_fin, Subtype.forall, not_forall] at h
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obtain ⟨a, ha⟩ := h
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obtain ⟨ha, ha2⟩ := ha
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apply Finset.prod_eq_zero (i := ⟨a, ha⟩)
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simp only [Finset.univ_eq_attach, Finset.mem_attach]
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apply Subtype.eq
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simp only [List.get_eq_getElem, ZeroMemClass.coe_zero]
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rw [timeContract_zero_of_diff_grade]
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simp [ha2]
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end WickContraction
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