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PhyslibAlpha.AlgebraicFramework.HilbertSpace.Unbounded.Cayley.Certificate

The bounded-unitary spectral interface

The bounded spectral theorem itself does not need the Cayley support condition from `Cayley/Measure.lean`: that condition is only needed once a bounded unitary's spectral measure is going to be pulled back to the real line. This file records the general output any construction of a bounded normal/unitary spectral measure must supply (`BoundedNormalSpectralData`, `BoundedUnitarySpectralData`), independently of how that measure is actually built — kept general so an arbitrary bounded normal operator can consume the same interface, not only Cayley unitaries.

`BoundedUnitarySpectralData` additionally exposes the real spectral measure obtained by pulling its (Cayley-supported) complex measure back through `cayleyInverseMap`, together with the exact uniqueness statement: a real spectral measure is determined by its Cayley pushforward.

- `BoundedNormalSpectralData` : a spectral measure reconstructing a bounded normal operator `U` in the weak identity-integral sense, with an integral-determined extensionality principle. - `BoundedUnitarySpectralData` : the same, plus the support condition needed to invert the Cayley map, and the resulting `realSpectralMeasure`.

A. Bounded normal spectral data

B. Bounded unitary spectral data

7 declarations

theorem

D.spectralMeasure=E.spectralMeasure  ⟹  D=ED.\text{spectralMeasure} = E.\text{spectralMeasure} \implies D = E for `BoundedNormalSpectralData`

Let UU be a bounded normal operator. Suppose DD and EE are two instances of bounded normal spectral data associated with UU. If their corresponding spectral measures are identical, then DD and EE are equal.

theorem

∫f dμD=∫f dμE  ⟹  D=E\int f \, d\mu_D = \int f \, d\mu_E \implies D = E for bounded normal spectral data

Let UU be a bounded normal operator on a complex Hilbert space. Let DD and EE be two instances of bounded normal spectral data associated with UU. If for every measurable function f:C→Cf : \mathbb{C} \to \mathbb{C} that is bounded (i.e., there exists a constant C∈RC \in \mathbb{R} such that ∥f(z)∥≤C\|f(z)\| \leq C for all z∈Cz \in \mathbb{C}), the bounded spectral integrals are equal: ∫Cf dμD=∫Cf dμE\int_{\mathbb{C}} f \, d\mu_D = \int_{\mathbb{C}} f \, d\mu_E (where μD\mu_D and μE\mu_E are the spectral measures associated with DD and EE respectively), then D=ED = E.

theorem

Extensionality of Bounded Unitary Spectral Data via Spectral Measure Equality

For any two sets of bounded unitary spectral data DD and EE associated with a bounded unitary operator uu, if their underlying spectral measures are equal, then the spectral data DD and EE are equal.

theorem

Equality of bounded spectral integrals implies D=ED = E for bounded unitary spectral data

Let uu be a bounded unitary operator on a complex Hilbert space. Let DD and EE be two sets of bounded unitary spectral data associated with uu. If for every measurable and bounded function f:C→Cf : \mathbb{C} \to \mathbb{C}, the bounded spectral integrals with respect to their corresponding spectral measures are equal, i.e., ∫Cf dμD=∫Cf dμE,\int_{\mathbb{C}} f \, d\mu_D = \int_{\mathbb{C}} f \, d\mu_E, then D=ED = E.

definition

The real spectral measure of DD on R\mathbb{R}

For a given set of bounded unitary spectral data DD on a Hilbert space HH, this definition constructs the spectral measure on the real line R\mathbb{R} by pulling back the complex spectral measure of DD through the inverse Cayley map. This resulting measure is an element of `WOTSpectralMeasure ℝ H`.

theorem

The Cayley map of DD's real spectral measure equals its complex spectral measure

Let DD be a set of bounded unitary spectral data on a Hilbert space HH. Let D.realSpectralMeasureD.\text{realSpectralMeasure} be the spectral measure on the real line R\mathbb{R} obtained by pulling back the complex spectral measure of DD through the inverse Cayley map. Then, the pushforward of D.realSpectralMeasureD.\text{realSpectralMeasure} under the Cayley map is equal to the original complex spectral measure D.spectralMeasureD.\text{spectralMeasure}.

theorem

Uniqueness of real spectral measure recovery from Cayley pushforward

Let DD be an instance of bounded unitary spectral data on a Hilbert space HH. For any spectral measure μS\mu_S on the real line R\mathbb{R} (of type `WOTSpectralMeasure ℝ H`), if the Cayley pushforward of μS\mu_S is equal to the complex spectral measure associated with DD (i.e., cayleyMap(μS)=D.spectralMeasure\text{cayleyMap}(\mu_S) = D.\text{spectralMeasure}), then μS\mu_S is equal to the canonical real spectral measure D.realSpectralMeasureD.\text{realSpectralMeasure} constructed from DD.