OAI/NumberTheory/DukePrimeDegree/Geometry/MatrixConjugationDensity.lean

GitHub source file

11 declarations, 0 contain sorry, 0 declared as axioms

Finite measures in the matrix conjugation representation

This is the elementary recurrence part of the needed Borel-density argument. A finite measure invariant under a strict real contraction is concentrated at zero. Applied to matrix coefficients, split diagonal conjugation forces invariant finite matrix measures onto diagonal matrices.

  1. theorem OAI.DukePrimeDegree.ae_zero_of_mul_map_eq line 28
  2. def OAI.DukePrimeDegree.diagonalMatrixConjugation line 52

    Source documentation

    Conjugation by the split real diagonal one-parameter subgroup.

    def diagonalMatrixConjugation {n : ℕ} (ell : Fin n → ℝ) (t : ℝ)
        (M : Matrix (Fin n) (Fin n) ℝ) : Matrix (Fin n) (Fin n) ℝ :=
    …
  3. lemma OAI.DukePrimeDegree.diagonalMatrixConjugation_entry line 57
  4. lemma OAI.DukePrimeDegree.continuous_diagonalMatrixConjugation line 65
  5. theorem OAI.DukePrimeDegree.ae_matrix_entry_zero_of_split_invariance line 76

    Source documentation

    Split diagonal invariance annihilates every nonzero weight.

    theorem ae_matrix_entry_zero_of_split_invariance {n : ℕ}
        (μ : Measure (Matrix (Fin n) (Fin n) ℝ)) [IsFiniteMeasure μ]
        (ell : Fin n → ℝ)
        (hdiag : ∀ t : ℝ, μ.map (diagonalMatrixConjugation ell t) = μ)
        (i j : Fin n) (hij : ell i ≠ ell j) : ∀ᵐ M ∂μ, M i j = 0 := by
    …

    Mentions: OAI.DukePrimeDegree.diagonalMatrixConjugation

  6. theorem OAI.DukePrimeDegree.ae_diagonal_of_split_invariance line 105

    Source documentation

    For a regular split diagonal subgroup, an invariant finite matrix measure is supported on the diagonal matrix space.

    theorem ae_diagonal_of_split_invariance {n : ℕ}
        (μ : Measure (Matrix (Fin n) (Fin n) ℝ)) [IsFiniteMeasure μ]
        (ell : Fin n → ℝ) (hell : Function.Injective ell)
        (hdiag : ∀ t : ℝ, μ.map (diagonalMatrixConjugation ell t) = μ) :
        ∀ᵐ M ∂μ, M = Matrix.diagonal (fun i => M i i) := by
    …

    Mentions: OAI.DukePrimeDegree.diagonalMatrixConjugation

  7. def OAI.DukePrimeDegree.rootMatrixConjugation line 127

    Source documentation

    Conjugation by a root unipotent matrix.

    def rootMatrixConjugation {n : ℕ} (i j : Fin n) (t : ℝ)
        (M : Matrix (Fin n) (Fin n) ℝ) : Matrix (Fin n) (Fin n) ℝ :=
    …
  8. lemma OAI.DukePrimeDegree.continuous_rootMatrixConjugation line 131
  9. theorem OAI.DukePrimeDegree.ae_diagonal_entries_eq_of_root_invariance line 138

    Source documentation

    Once the matrix measure is diagonal, one invariant root forces the two corresponding diagonal entries to coincide.

    theorem ae_diagonal_entries_eq_of_root_invariance {n : ℕ}
        (μ : Measure (Matrix (Fin n) (Fin n) ℝ))
        (hD : ∀ᵐ M ∂μ, M = Matrix.diagonal (fun i => M i i))
        (i j : Fin n) (hij : i ≠ j)
        (hroot : μ.map (rootMatrixConjugation i j 1) = μ) :
        ∀ᵐ M ∂μ, M i i = M j j := by
    …

    Mentions: OAI.DukePrimeDegree.rootMatrixConjugation

  10. theorem OAI.DukePrimeDegree.ae_blockScalar_of_conjugation_invariance line 170

    Source documentation

    Finite matrix measures invariant under split diagonals and the within-block root groups are concentrated on the block-scalar algebra.

    theorem ae_blockScalar_of_conjugation_invariance {n : ℕ}
        (μ : Measure (Matrix (Fin n) (Fin n) ℝ)) [IsFiniteMeasure μ]
        (ell : Fin n → ℝ) (hell : Function.Injective ell)
        (hdiag : ∀ t : ℝ, μ.map (diagonalMatrixConjugation ell t) = μ)
        (r : Setoid (Fin n))
        (hroot : ∀ i j, i ≠ j → r i j → μ.map (rootMatrixConjugation i j 1) = μ) :
        ∀ᵐ M ∂μ, M ∈ blockScalarAlgebra r := by
    …

    Mentions: OAI.DukePrimeDegree.diagonalMatrixConjugation, OAI.DukePrimeDegree.rootMatrixConjugation, OAI.DukePrimeDegree.blockScalarAlgebra

  11. theorem OAI.DukePrimeDegree.support_subset_blockScalar_of_conjugation_invariance line 195

    Source documentation

    The same conclusion holds at every point of the measure's support. This is the form used by a continuous conjugation-orbit map.

    theorem support_subset_blockScalar_of_conjugation_invariance {n : ℕ}
        (μ : Measure (Matrix (Fin n) (Fin n) ℝ)) [IsFiniteMeasure μ]
        (ell : Fin n → ℝ) (hell : Function.Injective ell)
        (hdiag : ∀ t : ℝ, μ.map (diagonalMatrixConjugation ell t) = μ)
        (r : Setoid (Fin n))
        (hroot : ∀ i j, i ≠ j → r i j → μ.map (rootMatrixConjugation i j 1) = μ) :
        μ.support ⊆ (blockScalarAlgebra r : Set (Matrix (Fin n) (Fin n) ℝ)) := by
    …

    Mentions: OAI.DukePrimeDegree.diagonalMatrixConjugation, OAI.DukePrimeDegree.rootMatrixConjugation, OAI.DukePrimeDegree.blockScalarAlgebra