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Mathlib.Analysis.CStarAlgebra.ContinuousFunctionalCalculus.Restrict

Restriction of the continuous functional calculus to a scalar subring #

The main declaration in this file is:

This will allow us to take an instance of the ContinuousFunctionalCalculus ℂ A IsStarNormal and produce both of the instances ContinuousFunctionalCalculus ℝ A IsSelfAdjoint and ContinuousFunctionalCalculus ℝ≥0 A (0 ≤ ·) simply by proving:

  1. IsSelfAdjoint x ↔ IsStarNormal x ∧ SpectrumRestricts Complex.re x,
  2. 0 ≤ x ↔ IsSelfAdjoint x ∧ SpectrumRestricts Real.toNNReal x.
def SpectrumRestricts.homeomorph {R : Type u_1} {S : Type u_2} {A : Type u_3} [Semifield R] [Semifield S] [Ring A] [Algebra R S] [Algebra R A] [Algebra S A] [IsScalarTower R S A] [TopologicalSpace R] [TopologicalSpace S] [ContinuousSMul R S] {a : A} {f : C(S, R)} (h : SpectrumRestricts a ⇑f) :
↑(spectrum S a) ≃ₜ ↑(spectrum R a)

The homeomorphism spectrum S a ≃ₜ spectrum R a induced by SpectrumRestricts a f.

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    theorem SpectrumRestricts.compactSpace {R : Type u_1} {S : Type u_2} {A : Type u_3} [Semifield R] [Semifield S] [Ring A] [Algebra R S] [Algebra R A] [Algebra S A] [IsScalarTower R S A] [TopologicalSpace R] [TopologicalSpace S] {a : A} (f : C(S, R)) (h : SpectrumRestricts a ⇑f) [h_cpct : CompactSpace ↑(spectrum S a)] :

    If the spectrum of an element restricts to a smaller scalar ring, then a continuous functional calculus over the larger scalar ring descends to the smaller one.

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      @[simp]
      theorem SpectrumRestricts.starAlgHom_apply {R : Type u} {S : Type v} {A : Type w} [Semifield R] [StarRing R] [TopologicalSpace R] [IsTopologicalSemiring R] [ContinuousStar R] [Semifield S] [StarRing S] [TopologicalSpace S] [IsTopologicalSemiring S] [ContinuousStar S] [Ring A] [StarRing A] [Algebra R S] [Algebra R A] [Algebra S A] [IsScalarTower R S A] [StarModule R S] [ContinuousSMul R S] {a : A} (φ : C(↑(spectrum S a), S) →⋆ₐ[S] A) {f : C(S, R)} (h : SpectrumRestricts a ⇑f) (a✝ : C(↑(spectrum R a), R)) :
      (starAlgHom φ h) a✝ = φ ({ toFun := ⇑(StarAlgHom.ofId R S), continuous_toFun := ⋯ }.comp (a✝.comp { toFun := Subtype.map ⇑f ⋯, continuous_toFun := ⋯ }))
      theorem SpectrumRestricts.starAlgHom_injective {R : Type u_1} {S : Type u_2} {A : Type u_3} [Semifield R] [StarRing R] [MetricSpace R] [IsTopologicalSemiring R] [ContinuousStar R] [Semifield S] [StarRing S] [MetricSpace S] [IsTopologicalSemiring S] [ContinuousStar S] [Ring A] [StarRing A] [Algebra S A] [Algebra R S] [Algebra R A] [IsScalarTower R S A] [StarModule R S] [ContinuousSMul R S] {a : A} {φ : C(↑(spectrum S a), S) →⋆ₐ[S] A} (hφ : Function.Injective ⇑φ) {f : C(S, R)} (h : SpectrumRestricts a ⇑f) (halg : Function.Injective ⇑(algebraMap R S)) :
      theorem SpectrumRestricts.continuous_starAlgHom {R : Type u_1} {S : Type u_2} {A : Type u_3} [Semifield R] [StarRing R] [MetricSpace R] [IsTopologicalSemiring R] [ContinuousStar R] [Semifield S] [StarRing S] [MetricSpace S] [IsTopologicalSemiring S] [ContinuousStar S] [Ring A] [StarRing A] [Algebra S A] [Algebra R S] [Algebra R A] [IsScalarTower R S A] [StarModule R S] [ContinuousSMul R S] [TopologicalSpace A] {a : A} {φ : C(↑(spectrum S a), S) →⋆ₐ[S] A} (hφ : Continuous ⇑φ) {f : C(S, R)} (h : SpectrumRestricts a ⇑f) :
      theorem SpectrumRestricts.cfc {R : Type u_1} {S : Type u_2} {A : Type u_3} {p q : A → Prop} [Semifield R] [StarRing R] [MetricSpace R] [IsTopologicalSemiring R] [ContinuousStar R] [Semifield S] [StarRing S] [MetricSpace S] [IsTopologicalSemiring S] [ContinuousStar S] [Ring A] [StarRing A] [Algebra S A] [Algebra R S] [Algebra R A] [IsScalarTower R S A] [StarModule R S] [ContinuousSMul R S] [TopologicalSpace A] [ContinuousFunctionalCalculus S A q] (f : C(S, R)) (halg : Topology.IsClosedEmbedding ⇑(algebraMap R S)) (h0 : p 0) (h : ∀ (a : A), p a ↔ q a ∧ SpectrumRestricts a ⇑f) :

      Given a ContinuousFunctionalCalculus S A q. If we form the predicate p for a : A characterized by: q a and the spectrum of a restricts to the scalar subring R via f : C(S, R), then we can get a restricted functional calculus ContinuousFunctionalCalculus R A p.

      theorem SpectrumRestricts.cfcHom_eq_restrict {R : Type u_1} {S : Type u_2} {A : Type u_3} {p q : A → Prop} [Semifield R] [StarRing R] [MetricSpace R] [IsTopologicalSemiring R] [ContinuousStar R] [Semifield S] [StarRing S] [MetricSpace S] [IsTopologicalSemiring S] [ContinuousStar S] [Ring A] [StarRing A] [Algebra S A] [Algebra R S] [Algebra R A] [IsScalarTower R S A] [StarModule R S] [ContinuousSMul R S] [TopologicalSpace A] [ContinuousFunctionalCalculus S A q] [ContinuousFunctionalCalculus R A p] [ContinuousMap.UniqueHom R A] (f : C(S, R)) {a : A} (hpa : p a) (hqa : q a) (h : SpectrumRestricts a ⇑f) :
      theorem SpectrumRestricts.cfc_eq_restrict {R : Type u_1} {S : Type u_2} {A : Type u_3} {p q : A → Prop} [Semifield R] [StarRing R] [MetricSpace R] [IsTopologicalSemiring R] [ContinuousStar R] [Semifield S] [StarRing S] [MetricSpace S] [IsTopologicalSemiring S] [ContinuousStar S] [Ring A] [StarRing A] [Algebra S A] [Algebra R S] [Algebra R A] [IsScalarTower R S A] [StarModule R S] [ContinuousSMul R S] [TopologicalSpace A] [ContinuousFunctionalCalculus S A q] [ContinuousFunctionalCalculus R A p] [ContinuousMap.UniqueHom R A] (f : C(S, R)) (halg : Topology.IsClosedEmbedding ⇑(algebraMap R S)) {a : A} (hpa : p a) (hqa : q a) (h : SpectrumRestricts a ⇑f) (g : R → R) :
      cfc g a = cfc (fun (x : S) => (algebraMap R S) (g (f x))) a

      Given a ContinuousFunctionalCalculus S A q. If we form the predicate p for a : A characterized by: q a and the spectrum of a restricts to the scalar subring R via f : C(S, R), then we can get a restricted functional calculus ContinuousFunctionalCalculus R A p.

      def QuasispectrumRestricts.homeomorph {R : Type u_1} {S : Type u_2} {A : Type u_3} [Semifield R] [Field S] [NonUnitalRing A] [Algebra R S] [Module R A] [Module S A] [IsScalarTower R S A] [TopologicalSpace R] [TopologicalSpace S] [ContinuousSMul R S] [IsScalarTower S A A] [SMulCommClass S A A] {a : A} {f : C(S, R)} (h : QuasispectrumRestricts a ⇑f) :

      The homeomorphism quasispectrum S a ≃ₜ quasispectrum R a induced by QuasispectrumRestricts a f.

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        If the quasispectrum of an element restricts to a smaller scalar ring, then a non-unital continuous functional calculus over the larger scalar ring descends to the smaller one.

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          @[simp]
          theorem QuasispectrumRestricts.nonUnitalStarAlgHom_apply {R : Type u} {S : Type v} {A : Type w} [Semifield R] [StarRing R] [TopologicalSpace R] [IsTopologicalSemiring R] [ContinuousStar R] [Field S] [StarRing S] [TopologicalSpace S] [IsTopologicalRing S] [ContinuousStar S] [NonUnitalRing A] [StarRing A] [Algebra R S] [Module R A] [Module S A] [IsScalarTower S A A] [SMulCommClass S A A] [IsScalarTower R S A] [StarModule R S] [ContinuousSMul R S] {a : A} (φ : ContinuousMapZero (↑(quasispectrum S a)) S →⋆ₙₐ[S] A) {f : C(S, R)} (h : QuasispectrumRestricts a ⇑f) (a✝ : ContinuousMapZero (↑(quasispectrum R a)) R) :
          (nonUnitalStarAlgHom φ h) a✝ = φ ({ toFun := ⇑(StarAlgHom.ofId R S), continuous_toFun := ⋯, map_zero' := ⋯ }.comp (a✝.comp { toFun := Subtype.map ⇑f ⋯, continuous_toFun := ⋯, map_zero' := ⋯ }))

          Given a NonUnitalContinuousFunctionalCalculus S A q. If we form the predicate p for a : A characterized by: q a and the quasispectrum of a restricts to the scalar subring R via f : C(S, R), then we can get a restricted functional calculus NonUnitalContinuousFunctionalCalculus R A p.

          theorem QuasispectrumRestricts.cfcₙ_eq_restrict {R : Type u_1} {S : Type u_2} {A : Type u_3} {p q : A → Prop} [Semifield R] [StarRing R] [MetricSpace R] [IsTopologicalSemiring R] [ContinuousStar R] [Field S] [StarRing S] [MetricSpace S] [IsTopologicalRing S] [ContinuousStar S] [NonUnitalRing A] [StarRing A] [Module S A] [IsScalarTower S A A] [SMulCommClass S A A] [Algebra R S] [Module R A] [IsScalarTower R S A] [StarModule R S] [ContinuousSMul R S] [TopologicalSpace A] [NonUnitalContinuousFunctionalCalculus S A q] [IsScalarTower R A A] [SMulCommClass R A A] [NonUnitalContinuousFunctionalCalculus R A p] [ContinuousMapZero.UniqueHom R A] (f : C(S, R)) (halg : Topology.IsClosedEmbedding ⇑(algebraMap R S)) {a : A} (hpa : p a) (hqa : q a) (h : QuasispectrumRestricts a ⇑f) (g : R → R) :
          cfcₙ g a = cfcₙ (fun (x : S) => (algebraMap R S) (g (f x))) a

          Given a NonUnitalContinuousFunctionalCalculus S A q. If we form the predicate p for a : A characterized by: q a and the quasispectrum of a restricts to the scalar subring R via f : C(S, R), then we can get a restricted functional calculus NonUnitalContinuousFunctionalCalculus R A p.