diff --git a/Nevanlinna/analyticOn_zeroSet.lean b/Nevanlinna/analyticOn_zeroSet.lean index 8a9cebc..b431384 100644 --- a/Nevanlinna/analyticOn_zeroSet.lean +++ b/Nevanlinna/analyticOn_zeroSet.lean @@ -233,3 +233,216 @@ theorem AnalyticOn.eliminateZeros rw [Finset.prod_insert] ring exact hb + + +theorem XX + {f : ℂ → ℂ} + {U : Set ℂ} + (hU : IsPreconnected U) + (h₁f : AnalyticOn ℂ f U) + (h₂f : ∃ u ∈ U, f u ≠ 0) : + ∀ (hu : u ∈ U), (h₁f u hu).order.toNat = (h₁f u hu).order := by + + intro hu + apply ENat.coe_toNat + by_contra C + rw [(h₁f u hu).order_eq_top_iff] at C + rw [← (h₁f u hu).frequently_zero_iff_eventually_zero] at C + obtain ⟨u₁, h₁u₁, h₂u₁⟩ := h₂f + rw [(h₁f.eqOn_zero_of_preconnected_of_frequently_eq_zero hU hu C) h₁u₁] at h₂u₁ + tauto + + +theorem discreteZeros + {f : ℂ → ℂ} + {U : Set ℂ} + (hU : IsPreconnected U) + (h₁f : AnalyticOn ℂ f U) + (h₂f : ∃ u ∈ U, f u ≠ 0) : + DiscreteTopology ↑(U ∩ f⁻¹' {0}) := by + + simp_rw [← singletons_open_iff_discrete] + simp_rw [Metric.isOpen_singleton_iff] + + intro z + + let A := XX hU h₁f h₂f z.2.1 + rw [eq_comm] at A + rw [AnalyticAt.order_eq_nat_iff] at A + obtain ⟨g, h₁g, h₂g, h₃g⟩ := A + + rw [Metric.eventually_nhds_iff_ball] at h₃g + have : ∃ ε > 0, ∀ y ∈ Metric.ball (↑z) ε, g y ≠ 0 := by + have h₄g : ContinuousAt g z := AnalyticAt.continuousAt h₁g + have : {0}ᶜ ∈ nhds (g z) := by + exact compl_singleton_mem_nhds_iff.mpr h₂g + + let F := h₄g.preimage_mem_nhds this + rw [Metric.mem_nhds_iff] at F + obtain ⟨ε, h₁ε, h₂ε⟩ := F + use ε + constructor; exact h₁ε + intro y hy + let G := h₂ε hy + simp at G + exact G + obtain ⟨ε₁, h₁ε₁⟩ := this + + obtain ⟨ε₂, h₁ε₂, h₂ε₂⟩ := h₃g + use min ε₁ ε₂ + constructor + · have : 0 < min ε₁ ε₂ := by + rw [lt_min_iff] + exact And.imp_right (fun _ => h₁ε₂) h₁ε₁ + exact this + + intro y + intro h₁y + + have h₂y : ↑y ∈ Metric.ball (↑z) ε₂ := by + simp + calc dist y z + _ < min ε₁ ε₂ := by assumption + _ ≤ ε₂ := by exact min_le_right ε₁ ε₂ + + have h₃y : ↑y ∈ Metric.ball (↑z) ε₁ := by + simp + calc dist y z + _ < min ε₁ ε₂ := by assumption + _ ≤ ε₁ := by exact min_le_left ε₁ ε₂ + + + have F := h₂ε₂ y.1 h₂y + rw [y.2.2] at F + simp at F + + have : g y.1 ≠ 0 := by + exact h₁ε₁.2 y h₃y + simp [this] at F + ext + rw [sub_eq_zero] at F + tauto + + +theorem finiteZeros + {f : ℂ → ℂ} + {U : Set ℂ} + (h₁U : IsPreconnected U) + (h₂U : IsCompact U) + (h₁f : AnalyticOn ℂ f U) + (h₂f : ∃ u ∈ U, f u ≠ 0) : + Set.Finite ↑(U ∩ f⁻¹' {0}) := by + + have hinter : IsCompact ↑(U ∩ f⁻¹' {0}) := by + apply IsCompact.of_isClosed_subset h₂U + apply h₁f.continuousOn.preimage_isClosed_of_isClosed + exact IsCompact.isClosed h₂U + exact isClosed_singleton + exact Set.inter_subset_left + + apply hinter.finite + apply DiscreteTopology.of_subset (s := ↑(U ∩ f⁻¹' {0})) + exact discreteZeros h₁U h₁f h₂f + rfl + + + +theorem AnalyticOnCompact.eliminateZeros + {f : ℂ → ℂ} + {U : Set ℂ} + (h₁U : IsPreconnected U) + (h₂U : IsCompact U) + (h₁f : AnalyticOn ℂ f U) + (h₂f : ∃ u ∈ U, f u ≠ 0) : + ∃ (g : ℂ → ℂ), AnalyticOn ℂ g U ∧ (∀ a ∈ U, g a ≠ 0) ∧ ∀ z, f z = (∏ a ∈ A, (z - a) ^ (n a)) • g z := by + + + let A := U ∩ f ⁻¹' {0} + + by sorry -- (finiteZeros h₁U h₂U h₁f h₂f).toFinset + let B := AnalyticOn.eliminateZeros h₁f + + + apply Finset.induction (α := U) (p := fun A ↦ (∀ a ∈ A, (hf a.1 a.2).order = n a) → ∃ (g : ℂ → ℂ), AnalyticOn ℂ g U ∧ (∀ a ∈ A, g a ≠ 0) ∧ ∀ z, f z = (∏ a ∈ A, (z - a) ^ (n a)) • g z) + + -- case empty + simp + use f + simp + exact hf + + -- case insert + intro b₀ B hb iHyp + intro hBinsert + obtain ⟨g₀, h₁g₀, h₂g₀, h₃g₀⟩ := iHyp (fun a ha ↦ hBinsert a (Finset.mem_insert_of_mem ha)) + + have : (h₁g₀ b₀ b₀.2).order = n b₀ := by + + rw [← hBinsert b₀ (Finset.mem_insert_self b₀ B)] + + let φ := fun z ↦ (∏ a ∈ B, (z - a.1) ^ n a.1) + + have : f = fun z ↦ φ z * g₀ z := by + funext z + rw [h₃g₀ z] + rfl + simp_rw [this] + + have h₁φ : AnalyticAt ℂ φ b₀ := by + dsimp [φ] + apply Finset.analyticAt_prod + intro b _ + apply AnalyticAt.pow + apply AnalyticAt.sub + apply analyticAt_id ℂ + exact analyticAt_const + + have h₂φ : h₁φ.order = (0 : ℕ) := by + rw [AnalyticAt.order_eq_nat_iff h₁φ 0] + use φ + constructor + · assumption + · constructor + · dsimp [φ] + push_neg + rw [Finset.prod_ne_zero_iff] + intro a ha + simp + have : ¬ (b₀.1 - a.1 = 0) := by + by_contra C + rw [sub_eq_zero] at C + rw [SetCoe.ext C] at hb + tauto + tauto + · simp + + rw [AnalyticAt.order_mul h₁φ (h₁g₀ b₀ b₀.2)] + + rw [h₂φ] + simp + + + obtain ⟨g₁, h₁g₁, h₂g₁, h₃g₁⟩ := (AnalyticOn.order_eq_nat_iff h₁g₀ b₀.2 (n b₀)).1 this + + use g₁ + constructor + · exact h₁g₁ + · constructor + · intro a h₁a + by_cases h₂a : a = b₀ + · rwa [h₂a] + · let A' := Finset.mem_of_mem_insert_of_ne h₁a h₂a + let B' := h₃g₁ a + let C' := h₂g₀ a A' + rw [B'] at C' + exact right_ne_zero_of_smul C' + · intro z + let A' := h₃g₀ z + rw [h₃g₁ z] at A' + rw [A'] + rw [← smul_assoc] + congr + simp + rw [Finset.prod_insert] + ring + exact hb diff --git a/Nevanlinna/holomorphic_zero.lean b/Nevanlinna/holomorphic_zero.lean index 2e5fbf7..a4017c6 100644 --- a/Nevanlinna/holomorphic_zero.lean +++ b/Nevanlinna/holomorphic_zero.lean @@ -282,186 +282,6 @@ theorem zeroDivisor_finiteOnCompact exact Set.inter_subset_right -theorem AnalyticOn.order_eq_nat_iff - {f : ℂ → ℂ} - {U : Set ℂ} - {z₀ : ℂ} - (hf : AnalyticOn ℂ f U) - (hz₀ : z₀ ∈ U) - (n : ℕ) : - (hf z₀ hz₀).order = ↑n ↔ ∃ (g : ℂ → ℂ), AnalyticOn ℂ g U ∧ g z₀ ≠ 0 ∧ ∀ z, f z = (z - z₀) ^ n • g z := by - - constructor - -- Direction → - intro hn - obtain ⟨gloc, h₁gloc, h₂gloc, h₃gloc⟩ := (AnalyticAt.order_eq_nat_iff (hf z₀ hz₀) n).1 hn - - -- Define a candidate function; this is (f z) / (z - z₀) ^ n with the - -- removable singularity removed - let g : ℂ → ℂ := fun z ↦ if z = z₀ then gloc z₀ else (f z) / (z - z₀) ^ n - - -- Describe g near z₀ - have g_near_z₀ : ∀ᶠ (z : ℂ) in nhds z₀, g z = gloc z := by - rw [eventually_nhds_iff] - obtain ⟨t, h₁t, h₂t, h₃t⟩ := eventually_nhds_iff.1 h₃gloc - use t - constructor - · intro y h₁y - by_cases h₂y : y = z₀ - · dsimp [g]; simp [h₂y] - · dsimp [g]; simp [h₂y] - rw [div_eq_iff_mul_eq, eq_comm, mul_comm] - exact h₁t y h₁y - norm_num - rw [sub_eq_zero] - tauto - · constructor - · assumption - · assumption - - -- Describe g near points z₁ that are different from z₀ - have g_near_z₁ {z₁ : ℂ} : z₁ ≠ z₀ → ∀ᶠ (z : ℂ) in nhds z₁, g z = f z / (z - z₀) ^ n := by - intro hz₁ - rw [eventually_nhds_iff] - use {z₀}ᶜ - constructor - · intro y hy - simp at hy - simp [g, hy] - · exact ⟨isOpen_compl_singleton, hz₁⟩ - - -- Use g and show that it has all required properties - use g - constructor - · -- AnalyticOn ℂ g U - intro z h₁z - by_cases h₂z : z = z₀ - · rw [h₂z] - apply AnalyticAt.congr h₁gloc - exact Filter.EventuallyEq.symm g_near_z₀ - · simp_rw [eq_comm] at g_near_z₁ - apply AnalyticAt.congr _ (g_near_z₁ h₂z) - apply AnalyticAt.div - exact hf z h₁z - apply AnalyticAt.pow - apply AnalyticAt.sub - apply analyticAt_id - apply analyticAt_const - simp - rw [sub_eq_zero] - tauto - · constructor - · simp [g]; tauto - · intro z - by_cases h₂z : z = z₀ - · rw [h₂z, g_near_z₀.self_of_nhds] - exact h₃gloc.self_of_nhds - · rw [(g_near_z₁ h₂z).self_of_nhds] - simp [h₂z] - rw [div_eq_mul_inv, mul_comm, mul_assoc, inv_mul_cancel] - simp; norm_num - rw [sub_eq_zero] - tauto - - -- direction ← - intro h - obtain ⟨g, h₁g, h₂g, h₃g⟩ := h - rw [AnalyticAt.order_eq_nat_iff] - use g - exact ⟨h₁g z₀ hz₀, ⟨h₂g, Filter.eventually_of_forall h₃g⟩⟩ - - -theorem AnalyticOn.order_eq_nat_iff' - {f : ℂ → ℂ} - {U : Set ℂ} - {A : Finset U} - (hf : AnalyticOn ℂ f U) - (n : A → ℕ) : - ∀ a : A, (hf a (Subtype.coe_prop a.val)).order = n a → ∃ (g : ℂ → ℂ), AnalyticOn ℂ g U ∧ (∀ a, g a ≠ 0) ∧ ∀ z, f z = (∏ a, (z - a) ^ (n a)) • g z := by - - apply Finset.induction - - let a : A := by sorry - let b : ℂ := by sorry - let u : U := by sorry - - let X := n a - have : a = (3 : ℂ) := by sorry - have : b ∈ ↑A := by sorry - have : ↑a ∈ U := by exact Subtype.coe_prop a.val - - let Y := ∀ a : A, (hf a (Subtype.coe_prop a.val)).order = n a - - --∀ a : A, (hf (ha a)).order = ↑(n a) → - - intro hn - obtain ⟨gloc, h₁gloc, h₂gloc, h₃gloc⟩ := (AnalyticAt.order_eq_nat_iff (hf z₀ hz₀) n).1 hn - - -- Define a candidate function - let g : ℂ → ℂ := fun z ↦ if z = z₀ then gloc z₀ else (f z) / (z - z₀) ^ n - - -- Describe g near z₀ - have g_near_z₀ : ∀ᶠ (z : ℂ) in nhds z₀, g z = gloc z := by - rw [eventually_nhds_iff] - obtain ⟨t, h₁t, h₂t, h₃t⟩ := eventually_nhds_iff.1 h₃gloc - use t - constructor - · intro y h₁y - by_cases h₂y : y = z₀ - · dsimp [g]; simp [h₂y] - · dsimp [g]; simp [h₂y] - rw [div_eq_iff_mul_eq, eq_comm, mul_comm] - exact h₁t y h₁y - norm_num - rw [sub_eq_zero] - tauto - · constructor - · assumption - · assumption - - -- Describe g near points z₁ different from z₀ - have g_near_z₁ {z₁ : ℂ} : z₁ ≠ z₀ → ∀ᶠ (z : ℂ) in nhds z₁, g z = f z / (z - z₀) ^ n := by - intro hz₁ - rw [eventually_nhds_iff] - use {z₀}ᶜ - constructor - · intro y hy - simp at hy - simp [g, hy] - · exact ⟨isOpen_compl_singleton, hz₁⟩ - - -- Use g and show that it has all required properties - use g - constructor - · -- AnalyticOn ℂ g U - intro z h₁z - by_cases h₂z : z = z₀ - · rw [h₂z] - apply AnalyticAt.congr h₁gloc - exact Filter.EventuallyEq.symm g_near_z₀ - · simp_rw [eq_comm] at g_near_z₁ - apply AnalyticAt.congr _ (g_near_z₁ h₂z) - apply AnalyticAt.div - exact hf z h₁z - apply AnalyticAt.pow - apply AnalyticAt.sub - apply analyticAt_id - apply analyticAt_const - simp - rw [sub_eq_zero] - tauto - · constructor - · simp [g]; tauto - · intro z - by_cases h₂z : z = z₀ - · rw [h₂z, g_near_z₀.self_of_nhds] - exact h₃gloc.self_of_nhds - · rw [(g_near_z₁ h₂z).self_of_nhds] - simp [h₂z] - rw [div_eq_mul_inv, mul_comm, mul_assoc, inv_mul_cancel] - simp; norm_num - rw [sub_eq_zero] - tauto noncomputable def zeroDivisorDegree