diff --git a/CommAlg/sayantan(dim_eq_dim_polynomial_add_one).lean b/CommAlg/sayantan(dim_eq_dim_polynomial_add_one).lean new file mode 100644 index 0000000..a9269a2 --- /dev/null +++ b/CommAlg/sayantan(dim_eq_dim_polynomial_add_one).lean @@ -0,0 +1,46 @@ +import Mathlib.RingTheory.Ideal.Basic +import Mathlib.Order.Height +import Mathlib.RingTheory.PrincipalIdealDomain +import Mathlib.RingTheory.DedekindDomain.Basic +import Mathlib.RingTheory.Ideal.Quotient +import Mathlib.RingTheory.Localization.AtPrime +import Mathlib.AlgebraicGeometry.PrimeSpectrum.Basic +import Mathlib.Order.ConditionallyCompleteLattice.Basic + +namespace Ideal + +variable {R : Type _} [CommRing R] (I : PrimeSpectrum R) +noncomputable def height : ℕ∞ := Set.chainHeight {J : PrimeSpectrum R | J < I} +noncomputable def krullDim (R : Type) [CommRing R] : WithBot ℕ∞ := ⨆ (I : PrimeSpectrum R), height I + +lemma height_def : height I = Set.chainHeight {J : PrimeSpectrum R | J < I} := rfl +lemma krullDim_def (R : Type) [CommRing R] : krullDim R = (⨆ (I : PrimeSpectrum R), height I : WithBot ℕ∞) := rfl +lemma krullDim_def' (R : Type) [CommRing R] : krullDim R = iSup (λ I : PrimeSpectrum R => (height I : WithBot ℕ∞)) := rfl + +noncomputable instance : CompleteLattice (WithBot (ℕ∞)) := WithBot.WithTop.completeLattice + +lemma dim_le_dim_polynomial_add_one [Nontrivial R] : + krullDim R + 1 ≤ krullDim (Polynomial R) := sorry -- Others are working on it + +-- private lemma sum_succ_of_succ_sum {ι : Type} (a : ℕ∞) [inst : Nonempty ι] : +-- (⨆ (x : ι), a + 1) = (⨆ (x : ι), a) + 1 := by +-- have : a + 1 = (⨆ (x : ι), a) + 1 := by rw [ciSup_const] +-- have : a + 1 = (⨆ (x : ι), a + 1) := Eq.symm ciSup_const +-- simp + +lemma dim_eq_dim_polynomial_add_one [Nontrivial R] [IsNoetherianRing R] : + krullDim R + 1 = krullDim (Polynomial R) := by + rw [le_antisymm_iff] + constructor + · exact dim_le_dim_polynomial_add_one + · unfold krullDim + have htPBdd : ∀ (P : PrimeSpectrum (Polynomial R)), (height P: WithBot ℕ∞) ≤ (⨆ (I : PrimeSpectrum R), ↑(height I + 1)) := by + intro P + unfold height + sorry + have : (⨆ (I : PrimeSpectrum R), ↑(height I) + 1) ≤ (⨆ (I : PrimeSpectrum R), ↑(height I)) + 1 := by + have : ∀ P : PrimeSpectrum R, ↑(height P) + 1 ≤ (⨆ (I : PrimeSpectrum R), ↑(height I)) + 1 := + fun _ ↦ add_le_add_right (le_iSup height _) 1 + apply iSup_le + exact this + sorry \ No newline at end of file