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TauCeti.Algebra.Lie.UniversalEnveloping.Kostant.RootSubgroup.Scheme.ToralClosure.Points

Points of the toral Kostant closure #

The closed group scheme kostantToralGroupScheme is generated inside GLₙ by the represented Kostant root subgroups together with the represented weight torus. This file identifies the corresponding formal inclusion on algebra-valued points. Its point subgroup contains both the pointwise elementary group and the represented torus, and hence contains their join.

For an arbitrary set S of root indices, write B_S(A) for the subgroup generated by the root subgroups indexed by S and the torus. After passing from automorphisms of the base-changed lattice to matrices in its chosen basis, the main theorem gives

B_S(A) ≤ kostantToralPointsSubgroup(A).

Taking S = Set.univ places the full torus--elementary subgroup assembled in TauCeti.Algebra.Lie.UniversalEnveloping.Kostant.RootSubgroup.Borel inside the points of the assembled scheme carrier. Equality over an algebraically closed field is a separate generation theorem and is not asserted here.

Main declarations #

References #

The construction is the pointwise face of the split torus and root-subgroup carrier in the Chevalley--Demazure construction; see J. E. Humphreys, Linear Algebraic Groups, §26, and R. W. Carter, Simple Groups of Lie Type, §§4.4 and 7.1.

noncomputable def TauCeti.UniversalEnvelopingAlgebra.kostantToralPointsSubgroup {L : Type u} [LieRing L] [LieAlgebra ℚ L] {I : Type w} {κ V : Type} [AddCommGroup V] [Module ℚ V] (e : I → L) (h : κ → L) (ρ : UniversalEnvelopingAlgebra ℚ L →ₐ[ℚ] Module.End ℚ V) (M : AddSubgroup V) (hM : ∀ u ∈ kostantForm e h, ∀ m ∈ M, (ρ u) m ∈ M) (hnil : ∀ (i : I), IsNilpotent (ρ ((UniversalEnvelopingAlgebra.ι ℚ) (e i)))) {n : ℕ} (b : Module.Basis (Fin n) ℤ ↥M) (wt : Fin n → κ → ℤ) [Finite κ] (A : Type v) [CommRing A] :
Subgroup (GL (Fin n) A)

The algebra-valued points of the toral Kostant closure, embedded in GLₙ through its Hopf-ideal quotient presentation.

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    theorem TauCeti.UniversalEnvelopingAlgebra.kostantToralPointsSubgroup_def {L : Type u} [LieRing L] [LieAlgebra ℚ L] {I : Type w} {κ V : Type} [AddCommGroup V] [Module ℚ V] (e : I → L) (h : κ → L) (ρ : UniversalEnvelopingAlgebra ℚ L →ₐ[ℚ] Module.End ℚ V) (M : AddSubgroup V) (hM : ∀ u ∈ kostantForm e h, ∀ m ∈ M, (ρ u) m ∈ M) (hnil : ∀ (i : I), IsNilpotent (ρ ((UniversalEnvelopingAlgebra.ι ℚ) (e i)))) {n : ℕ} (b : Module.Basis (Fin n) ℤ ↥M) (wt : Fin n → κ → ℤ) [Finite κ] (A : Type v) [CommRing A] :

    The toral-closure points are the general-linear point subgroup cut out by the toral defining Hopf ideal.

    @[simp]
    theorem TauCeti.UniversalEnvelopingAlgebra.mem_kostantToralPointsSubgroup_iff {L : Type u} [LieRing L] [LieAlgebra ℚ L] {I : Type w} {κ V : Type} [AddCommGroup V] [Module ℚ V] (e : I → L) (h : κ → L) (ρ : UniversalEnvelopingAlgebra ℚ L →ₐ[ℚ] Module.End ℚ V) (M : AddSubgroup V) (hM : ∀ u ∈ kostantForm e h, ∀ m ∈ M, (ρ u) m ∈ M) (hnil : ∀ (i : I), IsNilpotent (ρ ((UniversalEnvelopingAlgebra.ι ℚ) (e i)))) {n : ℕ} (b : Module.Basis (Fin n) ℤ ↥M) (wt : Fin n → κ → ℤ) [Finite κ] (A : Type v) [CommRing A] (g : GL (Fin n) A) :
    g ∈ kostantToralPointsSubgroup e h ρ M hM hnil b wt A ↔ ∀ x ∈ kostantToralDefiningIdeal e h ρ M hM hnil b wt, ((GeneralLinear.pointsMulEquiv n).symm g).ofConv x = 0

    Membership in the points of the toral closure is vanishing on its defining Hopf ideal.

    theorem TauCeti.UniversalEnvelopingAlgebra.kostantGeneratedPointsSubgroup_le_toralPoints {L : Type u} [LieRing L] [LieAlgebra ℚ L] {I : Type w} {κ V : Type} [AddCommGroup V] [Module ℚ V] (e : I → L) (h : κ → L) (ρ : UniversalEnvelopingAlgebra ℚ L →ₐ[ℚ] Module.End ℚ V) (M : AddSubgroup V) (hM : ∀ u ∈ kostantForm e h, ∀ m ∈ M, (ρ u) m ∈ M) (hnil : ∀ (i : I), IsNilpotent (ρ ((UniversalEnvelopingAlgebra.ι ℚ) (e i)))) {n : ℕ} (b : Module.Basis (Fin n) ℤ ↥M) (wt : Fin n → κ → ℤ) [Finite κ] (A : Type v) [CommRing A] :
    kostantGeneratedPointsSubgroup e h ρ M hM hnil b A ≤ kostantToralPointsSubgroup e h ρ M hM hnil b wt A

    The algebra-valued point subgroup of the toral closure contains the root-generated point subgroup: adjoining the weight torus to the generators enlarges the represented point subgroup (by shrinking the defining ideal).

    theorem TauCeti.UniversalEnvelopingAlgebra.kostantTorusMatrix_mem_toralPoints {L : Type u} [LieRing L] [LieAlgebra ℚ L] {I : Type w} {κ V : Type} [AddCommGroup V] [Module ℚ V] (e : I → L) (h : κ → L) (ρ : UniversalEnvelopingAlgebra ℚ L →ₐ[ℚ] Module.End ℚ V) (M : AddSubgroup V) (hM : ∀ u ∈ kostantForm e h, ∀ m ∈ M, (ρ u) m ∈ M) (hnil : ∀ (i : I), IsNilpotent (ρ ((UniversalEnvelopingAlgebra.ι ℚ) (e i)))) {n : ℕ} (b : Module.Basis (Fin n) ℤ ↥M) (wt : Fin n → κ → ℤ) [Fintype κ] (A : Type v) [CommRing A] (s : κ → Aˣ) :
    (kostantTorusMatrix M b wt) s ∈ kostantToralPointsSubgroup e h ρ M hM hnil b wt A

    Every represented weight-torus matrix is a point of the toral closure.

    The canonical subgroups of the toral-closure points #

    noncomputable def TauCeti.UniversalEnvelopingAlgebra.kostantToralRootSubgroupPoints {L : Type u} [LieRing L] [LieAlgebra ℚ L] {I : Type w} {κ V : Type} [AddCommGroup V] [Module ℚ V] (e : I → L) (h : κ → L) (ρ : UniversalEnvelopingAlgebra ℚ L →ₐ[ℚ] Module.End ℚ V) (M : AddSubgroup V) (hM : ∀ u ∈ kostantForm e h, ∀ m ∈ M, (ρ u) m ∈ M) (hnil : ∀ (i : I), IsNilpotent (ρ ((UniversalEnvelopingAlgebra.ι ℚ) (e i)))) {n : ℕ} (b : Module.Basis (Fin n) ℤ ↥M) (wt : Fin n → κ → ℤ) [Fintype κ] (i : I) (A : Type v) [CommRing A] :
    Multiplicative A →* ↥(kostantToralPointsSubgroup e h ρ M hM hnil b wt A)

    The canonical root-subgroup homomorphism into the matrix-valued points of the toral Kostant closure. The parameter is read through the multiplicative copy of the additive group.

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      @[simp]
      theorem TauCeti.UniversalEnvelopingAlgebra.coe_kostantToralRootSubgroupPoints {L : Type u} [LieRing L] [LieAlgebra ℚ L] {I : Type w} {κ V : Type} [AddCommGroup V] [Module ℚ V] (e : I → L) (h : κ → L) (ρ : UniversalEnvelopingAlgebra ℚ L →ₐ[ℚ] Module.End ℚ V) (M : AddSubgroup V) (hM : ∀ u ∈ kostantForm e h, ∀ m ∈ M, (ρ u) m ∈ M) (hnil : ∀ (i : I), IsNilpotent (ρ ((UniversalEnvelopingAlgebra.ι ℚ) (e i)))) {n : ℕ} (b : Module.Basis (Fin n) ℤ ↥M) (wt : Fin n → κ → ℤ) [Fintype κ] (i : I) (A : Type v) [CommRing A] (u : Multiplicative A) :
      ↑((kostantToralRootSubgroupPoints e h ρ M hM hnil b wt i A) u) = (kostantRootSubgroupMatrix e h ρ M hM i ⋯ b) (AdditiveGroup.gaPointsMulEquiv.symm u)

      The canonical toral-closure root-subgroup point is its represented divided-power exponential matrix.

      noncomputable def TauCeti.UniversalEnvelopingAlgebra.kostantToralWeightTorusPoints {L : Type u} [LieRing L] [LieAlgebra ℚ L] {I : Type w} {κ V : Type} [AddCommGroup V] [Module ℚ V] (e : I → L) (h : κ → L) (ρ : UniversalEnvelopingAlgebra ℚ L →ₐ[ℚ] Module.End ℚ V) (M : AddSubgroup V) (hM : ∀ u ∈ kostantForm e h, ∀ m ∈ M, (ρ u) m ∈ M) (hnil : ∀ (i : I), IsNilpotent (ρ ((UniversalEnvelopingAlgebra.ι ℚ) (e i)))) {n : ℕ} (b : Module.Basis (Fin n) ℤ ↥M) (wt : Fin n → κ → ℤ) [Fintype κ] (A : Type v) [CommRing A] :
      (κ → Aˣ) →* ↥(kostantToralPointsSubgroup e h ρ M hM hnil b wt A)

      The canonical weight-torus homomorphism into the matrix-valued points of the toral Kostant closure.

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        @[simp]
        theorem TauCeti.UniversalEnvelopingAlgebra.coe_kostantToralWeightTorusPoints {L : Type u} [LieRing L] [LieAlgebra ℚ L] {I : Type w} {κ V : Type} [AddCommGroup V] [Module ℚ V] (e : I → L) (h : κ → L) (ρ : UniversalEnvelopingAlgebra ℚ L →ₐ[ℚ] Module.End ℚ V) (M : AddSubgroup V) (hM : ∀ u ∈ kostantForm e h, ∀ m ∈ M, (ρ u) m ∈ M) (hnil : ∀ (i : I), IsNilpotent (ρ ((UniversalEnvelopingAlgebra.ι ℚ) (e i)))) {n : ℕ} (b : Module.Basis (Fin n) ℤ ↥M) (wt : Fin n → κ → ℤ) [Fintype κ] (A : Type v) [CommRing A] (s : κ → Aˣ) :
        ↑((kostantToralWeightTorusPoints e h ρ M hM hnil b wt A) s) = (kostantTorusMatrix M b wt) s

        The canonical toral-closure weight-torus point is its diagonal weight matrix.

        @[reducible, inline]
        noncomputable abbrev TauCeti.UniversalEnvelopingAlgebra.kostantToralPointsPresentation {L : Type u} [LieRing L] [LieAlgebra ℚ L] {I : Type w} {κ V : Type} [AddCommGroup V] [Module ℚ V] (e : I → L) (h : κ → L) (ρ : UniversalEnvelopingAlgebra ℚ L →ₐ[ℚ] Module.End ℚ V) (M : AddSubgroup V) (hM : ∀ u ∈ kostantForm e h, ∀ m ∈ M, (ρ u) m ∈ M) (hnil : ∀ (i : I), IsNilpotent (ρ ((UniversalEnvelopingAlgebra.ι ℚ) (e i)))) {n : ℕ} (b : Module.Basis (Fin n) ℤ ↥M) (wt : Fin n → κ → ℤ) [Fintype κ] (A : Type v) [CommRing A] :

        The integral-points presentation of the toral Kostant closure.

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          @[simp]
          theorem TauCeti.UniversalEnvelopingAlgebra.map_kostantToralRootSubgroupPoints {L : Type u} [LieRing L] [LieAlgebra ℚ L] {I : Type w} {κ V : Type} [AddCommGroup V] [Module ℚ V] (e : I → L) (h : κ → L) (ρ : UniversalEnvelopingAlgebra ℚ L →ₐ[ℚ] Module.End ℚ V) (M : AddSubgroup V) (hM : ∀ u ∈ kostantForm e h, ∀ m ∈ M, (ρ u) m ∈ M) (hnil : ∀ (i : I), IsNilpotent (ρ ((UniversalEnvelopingAlgebra.ι ℚ) (e i)))) {n : ℕ} (b : Module.Basis (Fin n) ℤ ↥M) (wt : Fin n → κ → ℤ) [Fintype κ] {A : Type v} {B : Type v'} [CommRing A] [CommRing B] (f : A →+* B) (i : I) (u : Multiplicative A) :
          ((kostantToralPointsPresentation e h ρ M hM hnil b wt A).map (kostantToralPointsPresentation e h ρ M hM hnil b wt B) f) ((kostantToralRootSubgroupPoints e h ρ M hM hnil b wt i A) u) = (kostantToralRootSubgroupPoints e h ρ M hM hnil b wt i B) (Multiplicative.ofAdd (f (Multiplicative.toAdd u)))

          The presented toral-closure root point is natural in the value ring.

          @[simp]
          theorem TauCeti.UniversalEnvelopingAlgebra.map_kostantToralWeightTorusPoints {L : Type u} [LieRing L] [LieAlgebra ℚ L] {I : Type w} {κ V : Type} [AddCommGroup V] [Module ℚ V] (e : I → L) (h : κ → L) (ρ : UniversalEnvelopingAlgebra ℚ L →ₐ[ℚ] Module.End ℚ V) (M : AddSubgroup V) (hM : ∀ u ∈ kostantForm e h, ∀ m ∈ M, (ρ u) m ∈ M) (hnil : ∀ (i : I), IsNilpotent (ρ ((UniversalEnvelopingAlgebra.ι ℚ) (e i)))) {n : ℕ} (b : Module.Basis (Fin n) ℤ ↥M) (wt : Fin n → κ → ℤ) [Fintype κ] {A : Type v} {B : Type v'} [CommRing A] [CommRing B] (f : A →+* B) (s : κ → Aˣ) :
          ((kostantToralPointsPresentation e h ρ M hM hnil b wt A).map (kostantToralPointsPresentation e h ρ M hM hnil b wt B) f) ((kostantToralWeightTorusPoints e h ρ M hM hnil b wt A) s) = (kostantToralWeightTorusPoints e h ρ M hM hnil b wt B) fun (i : κ) => (Units.map ↑f) (s i)

          The presented toral-closure weight-torus point is natural in the value ring.

          theorem TauCeti.UniversalEnvelopingAlgebra.kostantToralWeightTorusPoints_conj_rootSubgroupPoints {L : Type u} [LieRing L] [LieAlgebra ℚ L] {I : Type w} {κ V : Type} [AddCommGroup V] [Module ℚ V] (e : I → L) (h : κ → L) (ρ : UniversalEnvelopingAlgebra ℚ L →ₐ[ℚ] Module.End ℚ V) (M : AddSubgroup V) (hM : ∀ u ∈ kostantForm e h, ∀ m ∈ M, (ρ u) m ∈ M) (hnil : ∀ (i : I), IsNilpotent (ρ ((UniversalEnvelopingAlgebra.ι ℚ) (e i)))) {n : ℕ} (b : Module.Basis (Fin n) ℤ ↥M) (wt : Fin n → κ → ℤ) [Fintype κ] (hwt : ∀ (x : Fin n), IsCartanWeightVector h ρ (wt x) ↑(b x)) {i : I} {α : κ → ℤ} (hα : ∀ (j : κ), ⁅h j, e i⁆ = ↑(α j) • e i) (A : Type v) [CommRing A] (s : κ → Aˣ) (u : Multiplicative A) :
          (kostantToralWeightTorusPoints e h ρ M hM hnil b wt A) s * (kostantToralRootSubgroupPoints e h ρ M hM hnil b wt i A) u * ((kostantToralWeightTorusPoints e h ρ M hM hnil b wt A) s)⁻¹ = (kostantToralRootSubgroupPoints e h ρ M hM hnil b wt i A) (Multiplicative.ofAdd (↑(torusCharacter s α) * Multiplicative.toAdd u))

          The pinning equation in the matrix-valued points of the toral Kostant closure. If e i has Cartan weight α, conjugation by the weight-torus point s rescales the root-subgroup parameter by α(s). This is not a simp lemma: the weight α is pinned only by the hypothesis hα, so simp could never infer it from the left-hand side.

          theorem TauCeti.UniversalEnvelopingAlgebra.map_kostantTorusSubsystemSubgroup_le_toralPoints {L : Type u} [LieRing L] [LieAlgebra ℚ L] {I : Type w} {κ V : Type} [AddCommGroup V] [Module ℚ V] (e : I → L) (h : κ → L) (ρ : UniversalEnvelopingAlgebra ℚ L →ₐ[ℚ] Module.End ℚ V) (M : AddSubgroup V) (hM : ∀ u ∈ kostantForm e h, ∀ m ∈ M, (ρ u) m ∈ M) (hnil : ∀ (i : I), IsNilpotent (ρ ((UniversalEnvelopingAlgebra.ι ℚ) (e i)))) {n : ℕ} (b : Module.Basis (Fin n) ℤ ↥M) (wt : Fin n → κ → ℤ) [Fintype κ] (S : Set I) (A : Type v) [CommRing A] :

          After writing automorphisms in the basis b, every subgroup generated by a set of represented root subgroups together with the weight torus lies in the points of the toral closure.

          Scheme-valued points #

          theorem TauCeti.UniversalEnvelopingAlgebra.kostantToralGroupScheme_eq_hopfSpec {L : Type u} [LieRing L] [LieAlgebra ℚ L] {I : Type w} {κ V : Type} [AddCommGroup V] [Module ℚ V] (e : I → L) (h : κ → L) (ρ : UniversalEnvelopingAlgebra ℚ L →ₐ[ℚ] Module.End ℚ V) (M : AddSubgroup V) (hM : ∀ u ∈ kostantForm e h, ∀ m ∈ M, (ρ u) m ∈ M) (hnil : ∀ (i : I), IsNilpotent (ρ ((UniversalEnvelopingAlgebra.ι ℚ) (e i)))) {n : ℕ} (b : Module.Basis (Fin n) ℤ ↥M) (wt : Fin n → κ → ℤ) [Finite κ] :

          The toral closure is represented by its quotient coordinate Hopf algebra.

          theorem TauCeti.UniversalEnvelopingAlgebra.kostantToralGroupScheme_X_left {L : Type u} [LieRing L] [LieAlgebra ℚ L] {I : Type w} {κ V : Type} [AddCommGroup V] [Module ℚ V] (e : I → L) (h : κ → L) (ρ : UniversalEnvelopingAlgebra ℚ L →ₐ[ℚ] Module.End ℚ V) (M : AddSubgroup V) (hM : ∀ u ∈ kostantForm e h, ∀ m ∈ M, (ρ u) m ∈ M) (hnil : ∀ (i : I), IsNilpotent (ρ ((UniversalEnvelopingAlgebra.ι ℚ) (e i)))) {n : ℕ} (b : Module.Basis (Fin n) ℤ ↥M) (wt : Fin n → κ → ℤ) [Finite κ] :

          The underlying scheme of the toral closure is the spectrum of its coordinate ring.

          noncomputable def TauCeti.UniversalEnvelopingAlgebra.kostantToralSchemePointMulEquiv {L : Type u} [LieRing L] [LieAlgebra ℚ L] {I : Type w} {κ V : Type} [AddCommGroup V] [Module ℚ V] (e : I → L) (h : κ → L) (ρ : UniversalEnvelopingAlgebra ℚ L →ₐ[ℚ] Module.End ℚ V) (M : AddSubgroup V) (hM : ∀ u ∈ kostantForm e h, ∀ m ∈ M, (ρ u) m ∈ M) (hnil : ∀ (i : I), IsNilpotent (ρ ((UniversalEnvelopingAlgebra.ι ℚ) (e i)))) {n : ℕ} (b : Module.Basis (Fin n) ℤ ↥M) (wt : Fin n → κ → ℤ) [Finite κ] (A : Type) [CommRing A] :

          Algebra-valued points of the toral closure, transported to scheme-valued points.

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            The underlying spectrum map of a quotient point of the toral closure.