Theorem: NumberField.Embeddings.finite_of_norm_le
File: Mathlib/NumberTheory/NumberField/Embeddings.lean

Proof steps:
state_before: K : Type u_1
inst✝⁴ : Field K
inst✝³ : NumberField K
A : Type u_2
inst✝² : NormedField A
inst✝¹ : IsAlgClosed A
inst✝ : NormedAlgebra ℚ A
B : ℝ
⊢ {x | IsIntegral ℤ x ∧ ∀ (φ : K →+* A), ‖φ x‖ ≤ B}.Finite
state_after: K : Type u_1
inst✝⁴ : Field K
inst✝³ : NumberField K
A : Type u_2
inst✝² : NormedField A
inst✝¹ : IsAlgClosed A
inst✝ : NormedAlgebra ℚ A
B : ℝ
C : ℕ := ⌈max B 1 ^ finrank ℚ K * ↑((finrank ℚ K).choose (finrank ℚ K / 2))⌉₊
⊢ {x | IsIntegral ℤ x ∧ ∀ (φ : K →+* A), ‖φ x‖ ≤ B}.Finite
tactic: let C := Nat.ceil (max B 1 ^ finrank ℚ K * (finrank ℚ K).choose (finrank ℚ K / 2))
state_before: K : Type u_1
inst✝⁴ : Field K
inst✝³ : NumberField K
A : Type u_2
inst✝² : NormedField A
inst✝¹ : IsAlgClosed A
inst✝ : NormedAlgebra ℚ A
B : ℝ
C : ℕ := ⌈max B 1 ^ finrank ℚ K * ↑((finrank ℚ K).choose (finrank ℚ K / 2))⌉₊
⊢ {x | IsIntegral ℤ x ∧ ∀ (φ : K →+* A), ‖φ x‖ ≤ B}.Finite
state_after: K : Type u_1
inst✝⁴ : Field K
inst✝³ : NumberField K
A : Type u_2
inst✝² : NormedField A
inst✝¹ : IsAlgClosed A
inst✝ : NormedAlgebra ℚ A
B : ℝ
C : ℕ := ⌈max B 1 ^ finrank ℚ K * ↑((finrank ℚ K).choose (finrank ℚ K / 2))⌉₊
this :
  (⋃ f,
      ⋃ (_ : f.natDegree ≤ finrank ℚ K ∧ ∀ (i : ℕ), f.coeff i ∈ Icc (-↑C) ↑C),
        ↑(map (algebraMap ℤ K) f).roots.toFinset).Finite
⊢ {x | IsIntegral ℤ x ∧ ∀ (φ : K →+* A), ‖φ x‖ ≤ B}.Finite
tactic: have := bUnion_roots_finite (algebraMap ℤ K) (finrank ℚ K) (finite_Icc (-C : ℤ) C)
state_before: K : Type u_1
inst✝⁴ : Field K
inst✝³ : NumberField K
A : Type u_2
inst✝² : NormedField A
inst✝¹ : IsAlgClosed A
inst✝ : NormedAlgebra ℚ A
B : ℝ
C : ℕ := ⌈max B 1 ^ finrank ℚ K * ↑((finrank ℚ K).choose (finrank ℚ K / 2))⌉₊
this :
  (⋃ f,
      ⋃ (_ : f.natDegree ≤ finrank ℚ K ∧ ∀ (i : ℕ), f.coeff i ∈ Icc (-↑C) ↑C),
        ↑(map (algebraMap ℤ K) f).roots.toFinset).Finite
⊢ {x | IsIntegral ℤ x ∧ ∀ (φ : K →+* A), ‖φ x‖ ≤ B}.Finite
state_after: K : Type u_1
inst✝⁴ : Field K
inst✝³ : NumberField K
A : Type u_2
inst✝² : NormedField A
inst✝¹ : IsAlgClosed A
inst✝ : NormedAlgebra ℚ A
B : ℝ
C : ℕ := ⌈max B 1 ^ finrank ℚ K * ↑((finrank ℚ K).choose (finrank ℚ K / 2))⌉₊
this :
  (⋃ f,
      ⋃ (_ : f.natDegree ≤ finrank ℚ K ∧ ∀ (i : ℕ), f.coeff i ∈ Icc (-↑C) ↑C),
        ↑(map (algebraMap ℤ K) f).roots.toFinset).Finite
x : K
hx : x ∈ {x | IsIntegral ℤ x ∧ ∀ (φ : K →+* A), ‖φ x‖ ≤ B}
⊢ x ∈
    ⋃ f,
      ⋃ (_ : f.natDegree ≤ finrank ℚ K ∧ ∀ (i : ℕ), f.coeff i ∈ Icc (-↑C) ↑C), ↑(map (algebraMap ℤ K) f).roots.toFinset
tactic: refine this.subset fun x hx => ?_
state_before: K : Type u_1
inst✝⁴ : Field K
inst✝³ : NumberField K
A : Type u_2
inst✝² : NormedField A
inst✝¹ : IsAlgClosed A
inst✝ : NormedAlgebra ℚ A
B : ℝ
C : ℕ := ⌈max B 1 ^ finrank ℚ K * ↑((finrank ℚ K).choose (finrank ℚ K / 2))⌉₊
this :
  (⋃ f,
      ⋃ (_ : f.natDegree ≤ finrank ℚ K ∧ ∀ (i : ℕ), f.coeff i ∈ Icc (-↑C) ↑C),
        ↑(map (algebraMap ℤ K) f).roots.toFinset).Finite
x : K
hx : x ∈ {x | IsIntegral ℤ x ∧ ∀ (φ : K →+* A), ‖φ x‖ ≤ B}
⊢ x ∈
    ⋃ f,
      ⋃ (_ : f.natDegree ≤ finrank ℚ K ∧ ∀ (i : ℕ), f.coeff i ∈ Icc (-↑C) ↑C), ↑(map (algebraMap ℤ K) f).roots.toFinset
state_after: K : Type u_1
inst✝⁴ : Field K
inst✝³ : NumberField K
A : Type u_2
inst✝² : NormedField A
inst✝¹ : IsAlgClosed A
inst✝ : NormedAlgebra ℚ A
B : ℝ
C : ℕ := ⌈max B 1 ^ finrank ℚ K * ↑((finrank ℚ K).choose (finrank ℚ K / 2))⌉₊
this :
  (⋃ f,
      ⋃ (_ : f.natDegree ≤ finrank ℚ K ∧ ∀ (i : ℕ), f.coeff i ∈ Icc (-↑C) ↑C),
        ↑(map (algebraMap ℤ K) f).roots.toFinset).Finite
x : K
hx : x ∈ {x | IsIntegral ℤ x ∧ ∀ (φ : K →+* A), ‖φ x‖ ≤ B}
⊢ ∃ i,
    ∃ (_ : i.natDegree ≤ finrank ℚ K ∧ ∀ (i_1 : ℕ), i.coeff i_1 ∈ Icc (-↑C) ↑C),
      x ∈ ↑(map (algebraMap ℤ K) i).roots.toFinset
tactic: simp_rw [mem_iUnion]
state_before: K : Type u_1
inst✝⁴ : Field K
inst✝³ : NumberField K
A : Type u_2
inst✝² : NormedField A
inst✝¹ : IsAlgClosed A
inst✝ : NormedAlgebra ℚ A
B : ℝ
C : ℕ := ⌈max B 1 ^ finrank ℚ K * ↑((finrank ℚ K).choose (finrank ℚ K / 2))⌉₊
this :
  (⋃ f,
      ⋃ (_ : f.natDegree ≤ finrank ℚ K ∧ ∀ (i : ℕ), f.coeff i ∈ Icc (-↑C) ↑C),
        ↑(map (algebraMap ℤ K) f).roots.toFinset).Finite
x : K
hx : x ∈ {x | IsIntegral ℤ x ∧ ∀ (φ : K →+* A), ‖φ x‖ ≤ B}
⊢ ∃ i,
    ∃ (_ : i.natDegree ≤ finrank ℚ K ∧ ∀ (i_1 : ℕ), i.coeff i_1 ∈ Icc (-↑C) ↑C),
      x ∈ ↑(map (algebraMap ℤ K) i).roots.toFinset
state_after: K : Type u_1
inst✝⁴ : Field K
inst✝³ : NumberField K
A : Type u_2
inst✝² : NormedField A
inst✝¹ : IsAlgClosed A
inst✝ : NormedAlgebra ℚ A
B : ℝ
C : ℕ := ⌈max B 1 ^ finrank ℚ K * ↑((finrank ℚ K).choose (finrank ℚ K / 2))⌉₊
this :
  (⋃ f,
      ⋃ (_ : f.natDegree ≤ finrank ℚ K ∧ ∀ (i : ℕ), f.coeff i ∈ Icc (-↑C) ↑C),
        ↑(map (algebraMap ℤ K) f).roots.toFinset).Finite
x : K
hx : x ∈ {x | IsIntegral ℤ x ∧ ∀ (φ : K →+* A), ‖φ x‖ ≤ B}
h_map_ℚ_minpoly : minpoly ℚ x = map (algebraMap ℤ ℚ) (minpoly ℤ x)
⊢ ∃ i,
    ∃ (_ : i.natDegree ≤ finrank ℚ K ∧ ∀ (i_1 : ℕ), i.coeff i_1 ∈ Icc (-↑C) ↑C),
      x ∈ ↑(map (algebraMap ℤ K) i).roots.toFinset
tactic: have h_map_ℚ_minpoly := minpoly.isIntegrallyClosed_eq_field_fractions' ℚ hx.1
state_before: K : Type u_1
inst✝⁴ : Field K
inst✝³ : NumberField K
A : Type u_2
inst✝² : NormedField A
inst✝¹ : IsAlgClosed A
inst✝ : NormedAlgebra ℚ A
B : ℝ
C : ℕ := ⌈max B 1 ^ finrank ℚ K * ↑((finrank ℚ K).choose (finrank ℚ K / 2))⌉₊
this :
  (⋃ f,
      ⋃ (_ : f.natDegree ≤ finrank ℚ K ∧ ∀ (i : ℕ), f.coeff i ∈ Icc (-↑C) ↑C),
        ↑(map (algebraMap ℤ K) f).roots.toFinset).Finite
x : K
hx : x ∈ {x | IsIntegral ℤ x ∧ ∀ (φ : K →+* A), ‖φ x‖ ≤ B}
h_map_ℚ_minpoly : minpoly ℚ x = map (algebraMap ℤ ℚ) (minpoly ℤ x)
⊢ ∃ i,
    ∃ (_ : i.natDegree ≤ finrank ℚ K ∧ ∀ (i_1 : ℕ), i.coeff i_1 ∈ Icc (-↑C) ↑C),
      x ∈ ↑(map (algebraMap ℤ K) i).roots.toFinset
state_after: case refine_1
K : Type u_1
inst✝⁴ : Field K
inst✝³ : NumberField K
A : Type u_2
inst✝² : NormedField A
inst✝¹ : IsAlgClosed A
inst✝ : NormedAlgebra ℚ A
B : ℝ
C : ℕ := ⌈max B 1 ^ finrank ℚ K * ↑((finrank ℚ K).choose (finrank ℚ K / 2))⌉₊
this :
  (⋃ f,
      ⋃ (_ : f.natDegree ≤ finrank ℚ K ∧ ∀ (i : ℕ), f.coeff i ∈ Icc (-↑C) ↑C),
        ↑(map (algebraMap ℤ K) f).roots.toFinset).Finite
x : K
hx : x ∈ {x | IsIntegral ℤ x ∧ ∀ (φ : K →+* A), ‖φ x‖ ≤ B}
h_map_ℚ_minpoly : minpoly ℚ x = map (algebraMap ℤ ℚ) (minpoly ℤ x)
⊢ (minpoly ℤ x).natDegree ≤ finrank ℚ K

case refine_2
K : Type u_1
inst✝⁴ : Field K
inst✝³ : NumberField K
A : Type u_2
inst✝² : NormedField A
inst✝¹ : IsAlgClosed A
inst✝ : NormedAlgebra ℚ A
B : ℝ
C : ℕ := ⌈max B 1 ^ finrank ℚ K * ↑((finrank ℚ K).choose (finrank ℚ K / 2))⌉₊
this :
  (⋃ f,
      ⋃ (_ : f.natDegree ≤ finrank ℚ K ∧ ∀ (i : ℕ), f.coeff i ∈ Icc (-↑C) ↑C),
        ↑(map (algebraMap ℤ K) f).roots.toFinset).Finite
x : K
hx : x ∈ {x | IsIntegral ℤ x ∧ ∀ (φ : K →+* A), ‖φ x‖ ≤ B}
h_map_ℚ_minpoly : minpoly ℚ x = map (algebraMap ℤ ℚ) (minpoly ℤ x)
i : ℕ
⊢ (minpoly ℤ x).coeff i ∈ Icc (-↑C) ↑C
tactic: refine ⟨_, ⟨?_, fun i => ?_⟩, mem_rootSet.2 ⟨minpoly.ne_zero hx.1, minpoly.aeval ℤ x⟩⟩
state_before: case refine_2
K : Type u_1
inst✝⁴ : Field K
inst✝³ : NumberField K
A : Type u_2
inst✝² : NormedField A
inst✝¹ : IsAlgClosed A
inst✝ : NormedAlgebra ℚ A
B : ℝ
C : ℕ := ⌈max B 1 ^ finrank ℚ K * ↑((finrank ℚ K).choose (finrank ℚ K / 2))⌉₊
this :
  (⋃ f,
      ⋃ (_ : f.natDegree ≤ finrank ℚ K ∧ ∀ (i : ℕ), f.coeff i ∈ Icc (-↑C) ↑C),
        ↑(map (algebraMap ℤ K) f).roots.toFinset).Finite
x : K
hx : x ∈ {x | IsIntegral ℤ x ∧ ∀ (φ : K →+* A), ‖φ x‖ ≤ B}
h_map_ℚ_minpoly : minpoly ℚ x = map (algebraMap ℤ ℚ) (minpoly ℤ x)
i : ℕ
⊢ (minpoly ℤ x).coeff i ∈ Icc (-↑C) ↑C
state_after: case refine_2
K : Type u_1
inst✝⁴ : Field K
inst✝³ : NumberField K
A : Type u_2
inst✝² : NormedField A
inst✝¹ : IsAlgClosed A
inst✝ : NormedAlgebra ℚ A
B : ℝ
C : ℕ := ⌈max B 1 ^ finrank ℚ K * ↑((finrank ℚ K).choose (finrank ℚ K / 2))⌉₊
this :
  (⋃ f,
      ⋃ (_ : f.natDegree ≤ finrank ℚ K ∧ ∀ (i : ℕ), f.coeff i ∈ Icc (-↑C) ↑C),
        ↑(map (algebraMap ℤ K) f).roots.toFinset).Finite
x : K
hx : x ∈ {x | IsIntegral ℤ x ∧ ∀ (φ : K →+* A), ‖φ x‖ ≤ B}
h_map_ℚ_minpoly : minpoly ℚ x = map (algebraMap ℤ ℚ) (minpoly ℤ x)
i : ℕ
⊢ ↑|(minpoly ℤ x).coeff i| ≤ ↑↑C
tactic: rw [mem_Icc, ← abs_le, ← @Int.cast_le ℝ]
state_before: case refine_2
K : Type u_1
inst✝⁴ : Field K
inst✝³ : NumberField K
A : Type u_2
inst✝² : NormedField A
inst✝¹ : IsAlgClosed A
inst✝ : NormedAlgebra ℚ A
B : ℝ
C : ℕ := ⌈max B 1 ^ finrank ℚ K * ↑((finrank ℚ K).choose (finrank ℚ K / 2))⌉₊
this :
  (⋃ f,
      ⋃ (_ : f.natDegree ≤ finrank ℚ K ∧ ∀ (i : ℕ), f.coeff i ∈ Icc (-↑C) ↑C),
        ↑(map (algebraMap ℤ K) f).roots.toFinset).Finite
x : K
hx : x ∈ {x | IsIntegral ℤ x ∧ ∀ (φ : K →+* A), ‖φ x‖ ≤ B}
h_map_ℚ_minpoly : minpoly ℚ x = map (algebraMap ℤ ℚ) (minpoly ℤ x)
i : ℕ
⊢ ↑|(minpoly ℤ x).coeff i| ≤ ↑↑C
state_after: case refine_2
K : Type u_1
inst✝⁴ : Field K
inst✝³ : NumberField K
A : Type u_2
inst✝² : NormedField A
inst✝¹ : IsAlgClosed A
inst✝ : NormedAlgebra ℚ A
B : ℝ
C : ℕ := ⌈max B 1 ^ finrank ℚ K * ↑((finrank ℚ K).choose (finrank ℚ K / 2))⌉₊
this :
  (⋃ f,
      ⋃ (_ : f.natDegree ≤ finrank ℚ K ∧ ∀ (i : ℕ), f.coeff i ∈ Icc (-↑C) ↑C),
        ↑(map (algebraMap ℤ K) f).roots.toFinset).Finite
x : K
hx : x ∈ {x | IsIntegral ℤ x ∧ ∀ (φ : K →+* A), ‖φ x‖ ≤ B}
h_map_ℚ_minpoly : minpoly ℚ x = map (algebraMap ℤ ℚ) (minpoly ℤ x)
i : ℕ
⊢ ↑|(minpoly ℤ x).coeff i| = ‖(minpoly ℚ x).coeff i‖
tactic: refine (Eq.trans_le ?_ <| coeff_bdd_of_norm_le hx.2 i).trans (Nat.le_ceil _)
state_before: case refine_2
K : Type u_1
inst✝⁴ : Field K
inst✝³ : NumberField K
A : Type u_2
inst✝² : NormedField A
inst✝¹ : IsAlgClosed A
inst✝ : NormedAlgebra ℚ A
B : ℝ
C : ℕ := ⌈max B 1 ^ finrank ℚ K * ↑((finrank ℚ K).choose (finrank ℚ K / 2))⌉₊
this :
  (⋃ f,
      ⋃ (_ : f.natDegree ≤ finrank ℚ K ∧ ∀ (i : ℕ), f.coeff i ∈ Icc (-↑C) ↑C),
        ↑(map (algebraMap ℤ K) f).roots.toFinset).Finite
x : K
hx : x ∈ {x | IsIntegral ℤ x ∧ ∀ (φ : K →+* A), ‖φ x‖ ≤ B}
h_map_ℚ_minpoly : minpoly ℚ x = map (algebraMap ℤ ℚ) (minpoly ℤ x)
i : ℕ
⊢ ↑|(minpoly ℤ x).coeff i| = ‖(minpoly ℚ x).coeff i‖
state_after: no goals
tactic: rw [h_map_ℚ_minpoly, coeff_map, eq_intCast, Int.norm_cast_rat, Int.norm_eq_abs, Int.cast_abs]