OAI/Analysis/OperatorAlgebra/ExpectationDensityRoots.lean

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Application of the hypertrace separation and Powers–Størmer estimates to an actual completely positive expectation.

  1. theorem OAI.WeakPureInfiniteness.densityRoot_finite_support line 16
  2. theorem OAI.WeakPureInfiniteness.expectation_finite_density_roots line 37

    Source documentation

    A finite tracial expectation supplies positive finite-rank density roots of norm at most one, approximately invariant under the prescribed unitaries.

    theorem expectation_finite_density_roots (M : VonNeumannAlgebra H)
        [PartialOrder M.toStarSubalgebra] [StarOrderedRing M.toStarSubalgebra]
        (τ : Pureness.TracialState M.toStarSubalgebra)
        (E : (H →L[ℂ] H) →L[ℂ] (H →L[ℂ] H))
        (hE : CompletelyPositive E) (hEr : ∀ T, E T ∈ M)
        (hEf : ∀ T, T ∈ M → E T = T)
        (a : I → selfAdjoint M.toStarSubalgebra) (u : J → unitary M.toStarSubalgebra)
        {ε : ℝ} (hε : 0 < ε) :
        ∃ (n : ℕ) (w : Fin n → ℝ) (x : Fin n → H),
          (∀ k, 0 ≤ w k) ∧ (∑ k, w k = 1) ∧ (∀ k, ‖x k‖ ≤ 1) ∧
          (∀ i, |(τ.functional (a i)).re -
            ∑ k, w k * (inner ℂ (x k) (((a i : M.toStarSubalgebra) : H →L[ℂ] H) (x k))).re| < ε) ∧
    …

    Mentions: OAI.Pureness.TracialState, OAI.WeakPureInfiniteness.CompletelyPositive