Module: Mathlib.RingTheory.Spectrum.Prime.ChevalleyComplexity

Goal state before:
pp: case succ
R : Type u_2
inst✝ : CommRing R
n✝ n : ℕ
IH :
  ∀ {M : Submodule ℤ R},
    1 ∈ M →
      ∀ (k : ℕ) (d : Multiset (Fin n)) (S : ConstructibleSetData (MvPolynomial (Fin n) R)),
        (∀ C ∈ S, C.n ≤ k) →
          (∀ C ∈ S, ∀ (j : Fin C.n), C.g j ∈ coeffsIn (Fin n) M ⊓ Submodule.restrictScalars ℤ (degreesLE R (Fin n) d)) →
            ∃ T,
              comap MvPolynomial.C '' S.toSet = T.toSet ∧
                ∀ C ∈ T,
                  C.n ≤ numBound k (fun i ↦ 1 + Multiset.count i (Multiset.map Fin.val d)) n ∧
                    ∀ (i : Fin C.n), C.g i ∈ M ^ degBound k (fun i ↦ 1 + Multiset.count i (Multiset.map Fin.val d)) n
M : Submodule ℤ R
hM : 1 ∈ M
k : ℕ
d : Multiset (Fin (n + 1))
S : ConstructibleSetData (MvPolynomial (Fin (n + 1)) R)
hSn : ∀ C ∈ S, C.n ≤ k
hS :
  ∀ C ∈ S, ∀ (j : Fin C.n), C.g j ∈ coeffsIn (Fin (n + 1)) M ⊓ Submodule.restrictScalars ℤ (degreesLE R (Fin (n + 1)) d)
e : MvPolynomial (Fin (n + 1)) R ≃ₐ[R] (MvPolynomial (Fin n) R)[X] := MvPolynomial.finSuccEquiv R n
S' : ConstructibleSetData (MvPolynomial (Fin n) R)[X] := ConstructibleSetData.map e.toRingEquiv.toRingHom S
hS' : S'.degBound ≤ k * (1 + Multiset.count 0 d)
B : Multiset (Fin n) := Finsupp.toMultiset (Finsupp.comapDomain Fin.succ (Multiset.toFinsupp d) ⋯)
⊢ ∃ T,
    comap MvPolynomial.C '' S.toSet = T.toSet ∧
      ∀ C ∈ T,
        C.n ≤ numBound k (fun i ↦ 1 + Multiset.count i (Multiset.map Fin.val d)) (n + 1) ∧
          ∀ (i : Fin C.n), C.g i ∈ M ^ degBound k (fun i ↦ 1 + Multiset.count i (Multiset.map Fin.val d)) (n + 1)

Tactic:
obtain ⟨T, hT₁, hT₂⟩ := chevalley_polynomialC
      (R := MvPolynomial (Fin n) R)
      (coeffsIn _ M ⊓ (degreesLE _ _ B).restrictScalars ℤ)
      (by simpa [MvPolynomial.coeff_one, apply_ite] using hM)
      S' (fun x hxS j k ↦ by
        simp only [ConstructibleSetData.map,
          RingEquiv.toRingHom_eq_coe, AlgEquiv.toRingEquiv_toRingHom, Finset.mem_image,
          BasicConstructibleSetData.map, RingHom.coe_coe, S', e] at hxS
        obtain ⟨C, hxS, rfl⟩ := hxS
        simp only [comp_apply, Submodule.mem_inf, mem_coeffsIn, Submodule.restrictScalars_mem,
          mem_degreesLE]
        constructor
        · intro d
          simp only [finSuccEquiv_coeff_coeff]
          exact (hS _ hxS _).1 _
        · simp only [B]
          replace hS := (hS _ hxS j).2
          simp only [Submodule.coe_restrictScalars, SetLike.mem_coe, mem_degreesLE,
            Multiset.le_iff_count, Finsupp.count_toMultiset, Finsupp.comapDomain_apply,
            Multiset.toFinsupp_apply, ← degreeOf_def] at hS ⊢
          intro a
          exact (degreeOf_coeff_finSuccEquiv (C.g j) a k).trans (hS _))

Goal state after:
case succ
R : Type u_2
inst✝ : CommRing R
n✝ n : ℕ
IH :
  ∀ {M : Submodule ℤ R},
    1 ∈ M →
      ∀ (k : ℕ) (d : Multiset (Fin n)) (S : ConstructibleSetData (MvPolynomial (Fin n) R)),
        (∀ C ∈ S, C.n ≤ k) →
          (∀ C ∈ S, ∀ (j : Fin C.n), C.g j ∈ coeffsIn (Fin n) M ⊓ Submodule.restrictScalars ℤ (degreesLE R (Fin n) d)) →
            ∃ T,
              comap MvPolynomial.C '' S.toSet = T.toSet ∧
                ∀ C ∈ T,
                  C.n ≤ numBound k (fun i ↦ 1 + Multiset.count i (Multiset.map Fin.val d)) n ∧
                    ∀ (i : Fin C.n), C.g i ∈ M ^ degBound k (fun i ↦ 1 + Multiset.count i (Multiset.map Fin.val d)) n
M : Submodule ℤ R
hM : 1 ∈ M
k : ℕ
d : Multiset (Fin (n + 1))
S : ConstructibleSetData (MvPolynomial (Fin (n + 1)) R)
hSn : ∀ C ∈ S, C.n ≤ k
hS :
  ∀ C ∈ S, ∀ (j : Fin C.n), C.g j ∈ coeffsIn (Fin (n + 1)) M ⊓ Submodule.restrictScalars ℤ (degreesLE R (Fin (n + 1)) d)
e : MvPolynomial (Fin (n + 1)) R ≃ₐ[R] (MvPolynomial (Fin n) R)[X] := MvPolynomial.finSuccEquiv R n
S' : ConstructibleSetData (MvPolynomial (Fin n) R)[X] := ConstructibleSetData.map e.toRingEquiv.toRingHom S
hS' : S'.degBound ≤ k * (1 + Multiset.count 0 d)
B : Multiset (Fin n) := Finsupp.toMultiset (Finsupp.comapDomain Fin.succ (Multiset.toFinsupp d) ⋯)
T : ConstructibleSetData (MvPolynomial (Fin n) R)
hT₁ : comap Polynomial.C '' S'.toSet = T.toSet
hT₂ :
  ∀ C ∈ T,
    C.n ≤ S'.degBound ∧
      ∀ (i : Fin C.n),
        C.g i ∈ (coeffsIn (Fin n) M ⊓ Submodule.restrictScalars ℤ (degreesLE R (Fin n) B)) ^ S'.degBound ^ S'.degBound
⊢ ∃ T,
    comap MvPolynomial.C '' S.toSet = T.toSet ∧
      ∀ C ∈ T,
        C.n ≤ numBound k (fun i ↦ 1 + Multiset.count i (Multiset.map Fin.val d)) (n + 1) ∧
          ∀ (i : Fin C.n), C.g i ∈ M ^ degBound k (fun i ↦ 1 + Multiset.count i (Multiset.map Fin.val d)) (n + 1)