Bounded Borel functions #
Bounded Borel functions on ℝ: the domain of the Borel functional calculus.
Equations
- CommutingRepetition.BorelCalc.Bdd g = (Measurable g ∧ ∃ (C : ℝ), ∀ (t : ℝ), |g t| ≤ C)
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Combinations of finite measures and the transfer principle #
Multiplying the test function by a fixed bounded Borel function #
The measure h⁺ dμ.
Equations
- CommutingRepetition.BorelCalc.IsCombo.wd μ h = μ.withDensity fun (t : ℝ) => ↑(h t).toNNReal
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The polarized form #
The quadratic form Q g ξ = ∫ g dν_ξ (as a complex number).
Equations
- CommutingRepetition.BorelCalc.Q E hE g ξ = ↑(∫ (t : ℝ), g t ∂CommutingRepetition.BorelCalc.ν E hE ξ)
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The polarized form: pol g ξ η = ⟪ξ, g(E) η⟫ for continuous g.
Equations
- One or more equations did not get rendered due to their size.
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Boundedness #
The polarized form as a bounded sesquilinear map.
Equations
- CommutingRepetition.BorelCalc.polForm E hE hg = (LinearMap.mk₂'ₛₗ (starRingEnd ℂ) (RingHom.id ℂ) (CommutingRepetition.BorelCalc.pol E hE g) ⋯ ⋯ ⋯ ⋯).mkContinuous₂ (2 * ⋯.choose) ⋯
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The Borel functional calculus #
The Borel functional calculus g(E) for a bounded Borel function g (junk value
0 otherwise): the operator of the polarized form of the spectral measures.
Equations
- CommutingRepetition.BorelCalc.bfc E hE g = if hg : CommutingRepetition.BorelCalc.Bdd g then InnerProductSpace.continuousLinearMapOfBilin (CommutingRepetition.BorelCalc.polForm E hE hg) else 0
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An operator is determined by its quadratic form.
On bounded continuous functions the Borel calculus is the continuous one.
Rewriting the operator inside bfc (the self-adjointness proof is transported).
Linearity #
Multiplicativity #
Step 1: for continuous g and Borel h, by transfer in h.
Step 2: for Borel g and h, by transfer in g.
Multiplicativity of the Borel functional calculus.
The spectral measure of h(E) ξ: ∫ g dν_{h(E)ξ} = ∫ g h² dν_ξ.