diff --git a/CommAlg/final_poly_type.lean b/CommAlg/final_poly_type.lean index 85b01a2..dd35253 100644 --- a/CommAlg/final_poly_type.lean +++ b/CommAlg/final_poly_type.lean @@ -5,7 +5,7 @@ import Mathlib.AlgebraicGeometry.PrimeSpectrum.Basic set_option maxHeartbeats 0 macro "ls" : tactic => `(tactic|library_search) --- New tactic "obviously" +-- From Kyle : New tactic "obviously" macro "obviously" : tactic => `(tactic| ( first @@ -15,6 +15,7 @@ macro "obviously" : tactic => | simp; tauto; done; dbg_trace "it was simp tauto" | rfl; done; dbg_trace "it was rfl" | norm_num; done; dbg_trace "it was norm_num" + | norm_cast; done; dbg_trace "it was norm_cast" | /-change (@Eq ℝ _ _);-/ linarith; done; dbg_trace "it was linarith" -- | gcongr; done | ring; done; dbg_trace "it was ring" @@ -40,7 +41,7 @@ example : Polynomial.eval (100 : ℚ) F = (2 : ℚ) := by refine Iff.mpr (Rat.ext_iff (Polynomial.eval 100 F) 2) ?_ simp only [Rat.ofNat_num, Rat.ofNat_den] rw [F] - simp + simp [simp] -- Treat polynomial f ∈ ℚ[X] as a function f : ℚ → ℚ @@ -50,11 +51,11 @@ end section noncomputable section -- Polynomial type of degree d @[simp] -def PolyType (f : ℤ → ℤ) (d : ℕ) := ∃ Poly : Polynomial ℚ, ∃ (N : ℤ), (∀ (n : ℤ), N ≤ n → f n = Polynomial.eval (n : ℚ) Poly) ∧ d = Polynomial.degree Poly +def PolyType (f : ℤ → ℤ) (d : ℕ) := + ∃ Poly : Polynomial ℚ, ∃ (N : ℤ), (∀ (n : ℤ), N ≤ n → f n = Polynomial.eval (n : ℚ) Poly) ∧ + d = Polynomial.degree Poly section -#check PolyType - example (f : ℤ → ℤ) (hf : ∀ x, f x = x ^ 2) : PolyType f 2 := by unfold PolyType sorry @@ -69,14 +70,12 @@ def Δ : (ℤ → ℤ) → ℕ → (ℤ → ℤ) -- (NO need to prove another direction) Constant polynomial function = constant function lemma Poly_constant (F : Polynomial ℚ) (c : ℚ) : - (F = Polynomial.C (c : ℚ)) ↔ (∀ r : ℚ, (Polynomial.eval r F) = (c : ℚ)) := by + (F = Polynomial.C (c : ℚ)) ↔ (∀ r : ℚ, (Polynomial.eval r F) = (c : ℚ)) := by constructor - · intro h - rintro r + · intro h r refine Iff.mpr (Rat.ext_iff (Polynomial.eval r F) c) ?_ simp only [Rat.ofNat_num, Rat.ofNat_den] - rw [h] - simp + simp [h] · sorry -- Get the polynomial G (X) = F (X + s) from the polynomial F(X) @@ -84,22 +83,15 @@ lemma Polynomial_shifting (F : Polynomial ℚ) (s : ℚ) : ∃ (G : Polynomial sorry -- Shifting doesn't change the polynomial type -lemma Poly_shifting (f : ℤ → ℤ) (g : ℤ → ℤ) (hf : PolyType f d) (s : ℤ) (hfg : ∀ (n : ℤ), f (n + s) = g (n)) : PolyType g d := by - simp only [PolyType] - rcases hf with ⟨F, hh⟩ - rcases hh with ⟨N,s1, s2⟩ - have this : ∃ (G : Polynomial ℚ), (∀ (x : ℚ), Polynomial.eval x G = Polynomial.eval (x + s) F) ∧ (Polynomial.degree G = Polynomial.degree F) := by - exact Polynomial_shifting F s - rcases this with ⟨Poly, h1, h2⟩ - use Poly - use N - constructor - · intro n - specialize s1 (n + s) - intro hN - have this1 : f (n + s) = Polynomial.eval (n + s : ℚ) F := by - sorry - sorry +lemma Poly_shifting (f : ℤ → ℤ) (g : ℤ → ℤ) (hf : PolyType f d) (s : ℕ) + (hfg : ∀ (n : ℤ), f (n + s) = g (n)) : PolyType g d := by + rcases hf with ⟨F, ⟨N, s1, s2⟩⟩ + rcases (Polynomial_shifting F s) with ⟨Poly, h1, h2⟩ + use Poly, N; constructor + · intro n hN + have this1 : f (n + s) = Polynomial.eval (n + (s : ℚ)) F := by + rw [s1 (n + s) (by linarith)]; norm_cast + rw [←hfg n, this1]; exact (h1 n).symm · rw [h2, s2] -- PolyType 0 = constant function @@ -132,8 +124,8 @@ lemma PolyType_0 (f : ℤ → ℤ) : (PolyType f 0) ↔ (∃ (c : ℤ), ∃ (N : -- Δ of 0 times preserves the function lemma Δ_0 (f : ℤ → ℤ) : (Δ f 0) = f := by rfl - --simp only [Δ] --- Δ of 1 times decreaes the polynomial type by one + +-- Δ of 1 times decreaes the polynomial type by one --can be golfed lemma Δ_1 (f : ℤ → ℤ) (d : ℕ) : PolyType f (d + 1) → PolyType (Δ f 1) d := by intro h simp only [PolyType, Δ, Int.cast_sub, exists_and_right] @@ -186,53 +178,21 @@ lemma Δ_d_PolyType_d_to_PolyType_0 (f : ℤ → ℤ) (d : ℕ): PolyType f d -- The "reverse" of Δ of 1 times increases the polynomial type by one lemma Δ_1_ (f : ℤ → ℤ) (d : ℕ) : PolyType (Δ f 1) d → PolyType f (d + 1) := by - intro h + rintro ⟨P, N, ⟨h1, h2⟩⟩ simp only [PolyType, Nat.cast_add, Nat.cast_one, exists_and_right] - rcases h with ⟨P, N, h⟩ - rcases h with ⟨h1, h2⟩ let G := fun (q : ℤ) => f (N) sorry - -lemma foo (d : ℕ) : (f : ℤ → ℤ) → (∃ (c : ℤ), ∃ (N : ℤ), (∀ (n : ℤ), N ≤ n → (Δ f d) (n) = c) ∧ c ≠ 0) → (PolyType f d) := by +lemma foo (d : ℕ) : (f : ℤ → ℤ) → (∃ (c : ℤ), ∃ (N : ℤ), (∀ (n : ℤ), N ≤ n → + (Δ f d) (n) = c) ∧ c ≠ 0) → (PolyType f d) := by induction' d with d hd - - -- Base case - · intro f - intro h - rcases h with ⟨c, N, hh⟩ - rw [PolyType_0] - use c - use N - tauto - - -- Induction step - · intro f - intro h - rcases h with ⟨c, N, h⟩ - have this : PolyType f (d + 1) := by - rcases h with ⟨H,c0⟩ - let g := (Δ f 1) - have this1 : (∃ (c : ℤ), ∃ (N : ℤ), (∀ (n : ℤ), N ≤ n → (Δ g d) (n) = c) ∧ c ≠ 0) := by - use c; use N - constructor - · intro n - specialize H n - intro h - have this : Δ f (d + 1) n = c := by tauto - rw [←this] - rw [Δ_1_s_equiv_Δ_s_1] - · tauto - have this2 : PolyType g d := by - apply hd - tauto - exact Δ_1_ f d this2 - exact this + · rintro f ⟨c, N, hh⟩; rw [PolyType_0 f]; exact ⟨c, N, hh⟩ + · exact fun f ⟨c, N, ⟨H, c0⟩⟩ => + Δ_1_ f d (hd (Δ f 1) ⟨c, N, fun n h => by rw [← H n h, Δ_1_s_equiv_Δ_s_1], c0⟩) -- [BH, 4.1.2] (a) => (b) -- Δ^d f (n) = c for some nonzero integer c for n >> 0 → f is of polynomial type d -lemma a_to_b (f : ℤ → ℤ) (d : ℕ) : (∃ (c : ℤ), ∃ (N : ℤ), (∀ (n : ℤ), N ≤ n → (Δ f d) (n) = c) ∧ c ≠ 0) → PolyType f d := by - sorry +lemma a_to_b (f : ℤ → ℤ) (d : ℕ) : (∃ (c : ℤ), ∃ (N : ℤ), (∀ (n : ℤ), N ≤ n → (Δ f d) (n) = c) ∧ c ≠ 0) → PolyType f d := fun h => (foo d f) h -- [BH, 4.1.2] (a) <= (b) -- f is of polynomial type d → Δ^d f (n) = c for some nonzero integer c for n >> 0 @@ -241,6 +201,7 @@ lemma b_to_a (f : ℤ → ℤ) (d : ℕ) (poly : PolyType f d) : rw [←PolyType_0]; exact Δ_d_PolyType_d_to_PolyType_0 f d poly end + -- @Additive lemma of length for a SES -- Given a SES 0 → A → B → C → 0, then length (A) - length (B) + length (C) = 0 section diff --git a/CommAlg/jayden(krull-dim-zero).lean b/CommAlg/jayden(krull-dim-zero).lean index 15dd150..921d6f8 100644 --- a/CommAlg/jayden(krull-dim-zero).lean +++ b/CommAlg/jayden(krull-dim-zero).lean @@ -16,6 +16,7 @@ import Mathlib.Order.ConditionallyCompleteLattice.Basic import Mathlib.Algebra.Ring.Pi import Mathlib.RingTheory.Finiteness import Mathlib.Util.PiNotation +import Mathlib.RingTheory.Ideal.MinimalPrime import CommAlg.krull open PiNotation @@ -43,6 +44,8 @@ class IsLocallyNilpotent {R : Type _} [CommRing R] (I : Ideal R) : Prop := #check Ideal.IsLocallyNilpotent end Ideal +def RingJacobson (R) [Ring R] := Ideal.jacobson (⊥ : Ideal R) + -- Repeats the definition of the length of a module by Monalisa variable (R : Type _) [CommRing R] (I J : Ideal R) variable (M : Type _) [AddCommMonoid M] [Module R M] @@ -169,15 +172,15 @@ abbrev Prod_of_localization := def foo : Prod_of_localization R →+* R where toFun := sorry -- invFun := sorry - left_inv := sorry - right_inv := sorry + --left_inv := sorry + --right_inv := sorry map_mul' := sorry map_add' := sorry def product_of_localization_at_maximal_ideal [Finite (MaximalSpectrum R)] - (h : Ideal.IsLocallyNilpotent (Ideal.jacobson (⊥ : Ideal R))) : - Prod_of_localization R ≃+* R := by sorry + (h : Ideal.IsLocallyNilpotent (RingJacobson R)) : + R ≃+* Prod_of_localization R := by sorry -- Stacks Lemma 10.53.6: R is Artinian iff R has finite length as an R-mod lemma IsArtinian_iff_finite_length : @@ -193,18 +196,61 @@ lemma primes_of_Artinian_are_maximal -- Lemma: Krull dimension of a ring is the supremum of height of maximal ideals +-- Lemma: X is an irreducible component of Spec(R) ↔ X = V(I) for I a minimal prime +lemma irred_comp_minmimal_prime (X) : + X ∈ irreducibleComponents (PrimeSpectrum R) + ↔ ∃ (P : minimalPrimes R), X = PrimeSpectrum.zeroLocus P := by + sorry + +-- Lemma: localization of Noetherian ring is Noetherian +-- lemma localization_of_Noetherian_at_prime [IsNoetherianRing R] +-- (atprime: Ideal.IsPrime I) : +-- IsNoetherianRing (Localization.AtPrime I) := by sorry + + -- Stacks Lemma 10.60.5: R is Artinian iff R is Noetherian of dimension 0 -lemma dim_le_zero_Noetherian_iff_Artinian (R : Type _) [CommRing R] : - IsNoetherianRing R ∧ Ideal.krullDim R ≤ 0 ↔ IsArtinianRing R := by - constructor +lemma Artinian_if_dim_le_zero_Noetherian (R : Type _) [CommRing R] : + IsNoetherianRing R ∧ Ideal.krullDim R ≤ 0 → IsArtinianRing R := by rintro ⟨RisNoetherian, dimzero⟩ rw [ring_Noetherian_iff_spec_Noetherian] at RisNoetherian + have := fun X => (irred_comp_minmimal_prime R X).mp + choose F hf using this let Z := irreducibleComponents (PrimeSpectrum R) - have Zfinite : Set.Finite Z := by + -- have Zfinite : Set.Finite Z := by -- apply TopologicalSpace.NoetherianSpace.finite_irreducibleComponents ?_ + -- sorry + --let P := fun + rw [← ring_Noetherian_iff_spec_Noetherian] at RisNoetherian + have PrimeIsMaximal : ∀ X : Z, Ideal.IsMaximal (F X X.2).1 := by + intro X + have prime : Ideal.IsPrime (F X X.2).1 := (F X X.2).2.1.1 + rw [Ideal.dim_le_zero_iff] at dimzero + exact dimzero ⟨_, prime⟩ + have JacLocallyNil : Ideal.IsLocallyNilpotent (RingJacobson R) := by sorry + let Loc := fun X : Z ↦ Localization.AtPrime (F X.1 X.2).1 + have LocNoetherian : ∀ X, IsNoetherianRing (Loc X) := by + intro X sorry - - sorry + -- apply IsLocalization.isNoetherianRing (F X.1 X.2).1 (Loc X) RisNoetherian + have Locdimzero : ∀ X, Ideal.krullDim (Loc X) ≤ 0 := by sorry + have powerannihilates : ∀ X, ∃ n : ℕ, + ((F X.1 X.2).1) ^ n • (⊤: Submodule R (Loc X)) = 0 := by sorry + have LocFinitelength : ∀ X, ∃ n : ℕ, Module.length R (Loc X) ≤ n := by + intro X + have idealfg : Ideal.FG (F X.1 X.2).1 := by + rw [isNoetherianRing_iff_ideal_fg] at RisNoetherian + specialize RisNoetherian (F X.1 X.2).1 + exact RisNoetherian + have modulefg : Module.Finite R (Loc X) := by sorry -- not sure if this is true + specialize PrimeIsMaximal X + specialize powerannihilates X + apply power_zero_finite_length R (F X.1 X.2).1 (Loc X) idealfg powerannihilates + have RingFinitelength : ∃ n : ℕ, Module.length R R ≤ n := by sorry + rw [IsArtinian_iff_finite_length] + exact RingFinitelength + +lemma dim_le_zero_Noetherian_if_Artinian (R : Type _) [CommRing R] : + IsArtinianRing R → IsNoetherianRing R ∧ Ideal.krullDim R ≤ 0 := by intro RisArtinian constructor apply finite_length_is_Noetherian @@ -213,7 +259,6 @@ lemma dim_le_zero_Noetherian_iff_Artinian (R : Type _) [CommRing R] : intro I apply primes_of_Artinian_are_maximal --- Use TopologicalSpace.NoetherianSpace.exists_finset_irreducible :