OAI/Analysis/KadisonKastler/FiniteDimensionalGap.lean

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Finite dimensionality across a small algebra gap

A finite net in the second unit ball produces a net of radius less than one in the first unit ball. Riesz's lemma then forces finite dimensionality. Only the fixed small constant needed in the type-stability argument is used.

  1. theorem OAI.KadisonKastler.finiteDimensional_of_unitBall_approx line 19
  2. theorem OAI.KadisonKastler.finiteDimensional_of_near_finiteDimensional line 73

    Source documentation

    A neighbor of a finite-dimensional algebra at the constant used in the finite-type theorem is itself finite-dimensional.

    theorem finiteDimensional_of_near_finiteDimensional
        (M N : VonNeumannAlgebra H) [FiniteDimensional ℂ (Algebra N)]
        (hgap : kkDistance M N < 1 / 10) : FiniteDimensional ℂ (Algebra M) := by
    …

    Mentions: OAI.KadisonKastler.Algebra, OAI.KadisonKastler.kkDistance