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MathlibAnnex.CStarAlgebra.CAR.stronglyConverges_shell_sums_of_trace_of_cyclic

Exact source: MathlibAnnex/Analysis/CStarAlgebra/CAR/TracialTransport.lean, lines 25–54.

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1import MathlibAnnex.Analysis.CStarAlgebra.CAR.TracialCyclic
2import MathlibAnnex.Analysis.CStarAlgebra.AtomicConstruction.GeneratedExt
3
4/-!
5# Transport between target-cyclic realizations of the source trace
6
7Source cyclicity is proved, not assumed. The source intertwiner passes to
8both strong shell sums, and norm generation then gives target intertwining.
9-/
10
11set_option autoImplicit false
12
13open Filter Topology
14open scoped InnerProduct
15
16namespace MathlibAnnex.CStarAlgebra.CAR
17
18open MathlibAnnex.Analysis.CStarAlgebra
19
20universe v w
21variable {H : Type v} [NormedAddCommGroup H] [InnerProductSpace ℂ H] [CompleteSpace H]
22variable {K : Type w} [NormedAddCommGroup K] [InnerProductSpace ℂ K] [CompleteSpace K]
23
24set_option maxHeartbeats 1000000 in
25/-- On a target-cyclic realization of the trace, the source shell sums
26converge strongly to the actual represented generator and its adjoint. -/
27theorem stronglyConverges_shell_sums_of_trace_of_cyclic
28    (family : RepresentativeShellFamily)
29    (ρ : Representation (ShellFamilyTarget family) H) (ξ : H)
30    (hξ : ∀ a, Representation.vectorFunctional
31      (ρ.comp (shellFamilySourceHom family)) ξ a = trace a)
32    (hcyclic : DenseRange (fun a ↦ ρ a ξ))
33    (i : MathlibAnnex.CStarAlgebra.PureState.GNSClass Limit) :
34    ContinuousLinearMap.StronglyConverges
35      (ContinuousLinearMap.partialSum (fun n ↦
36        ρ (shellFamilySourceHom family ((representativeShellData family i).link n))))
37      atTop (ρ (shellFamilyGenerator family i)) ∧
38    ContinuousLinearMap.StronglyConverges
39      (ContinuousLinearMap.partialSum (fun n ↦
40        (ρ (shellFamilySourceHom family ((representativeShellData family i).link n)))†))
41      atTop ((ρ (shellFamilyGenerator family i))†) := by
42  obtain ⟨S, T, hS, hT, _, _, _, heq⟩ :=
43    exists_shell_sums_eq_on_cyclicSubspace family ρ ξ hξ i
44  have htop := cyclicSubspace_eq_top_of_trace_of_cyclic family ρ ξ hξ hcyclic
45  have hall (x : H) : ρ (shellFamilyGenerator family i) x = S x ∧
46      ((ρ (shellFamilyGenerator family i))†) x = T x := by
47    apply heq x
48    rw [htop]
49    trivial
50  have hS_eq : S = ρ (shellFamilyGenerator family i) :=
51    ContinuousLinearMap.ext fun x ↦ (hall x).1.symm
52  have hT_eq : T = (ρ (shellFamilyGenerator family i))† :=
53    ContinuousLinearMap.ext fun x ↦ (hall x).2.symm
54  exact ⟨hS_eq ▸ hS, hT_eq ▸ hT⟩
55
56private theorem comp_partialSum_eq_partialSum_comp
57    (e : H →L[ℂ] K) (A : ℕ → H →L[ℂ] H) (B : ℕ → K →L[ℂ] K)
58    (h : ∀ n, e.comp (A n) = (B n).comp e) (N : ℕ) :
59    e.comp (ContinuousLinearMap.partialSum A N) =
60      (ContinuousLinearMap.partialSum B N).comp e := by
61  ext x
62  simp only [ContinuousLinearMap.comp_apply, ContinuousLinearMap.partialSum_apply, map_sum]
63  apply Finset.sum_congr rfl
64  intro n _
65  exact congrArg (fun T : H →L[ℂ] K ↦ T x) (h n)
66
67/-- Two cyclic target representations of the source trace are pointed
68unitarily equivalent on the whole target, including every added generator. -/
69theorem exists_pointed_unitary_of_trace_of_cyclic
70    (family : RepresentativeShellFamily)
71    (ρ : Representation (ShellFamilyTarget family) H)
72    (σ : Representation (ShellFamilyTarget family) K) (ξ : H) (η : K)
73    (hξ : ∀ a, Representation.vectorFunctional
74      (ρ.comp (shellFamilySourceHom family)) ξ a = trace a)
75    (hη : ∀ a, Representation.vectorFunctional
76      (σ.comp (shellFamilySourceHom family)) η a = trace a)
77    (hρ : DenseRange (fun a ↦ ρ a ξ)) (hσ : DenseRange (fun a ↦ σ a η)) :
78    ∃ e : H ≃ₗᵢ[ℂ] K, e ξ = η ∧
79      ∀ a, (e : H →L[ℂ] K).comp (ρ a) = (σ a).comp (e : H →L[ℂ] K) := by
80  let ρB := ρ.comp (shellFamilySourceHom family)
81  let σB := σ.comp (shellFamilySourceHom family)
82  have hdρ : DenseRange (StarAlgHom.orbitMap ρB ξ) :=
83    denseRange_source_orbit_of_trace_of_cyclic family ρ ξ hξ hρ
84  have hdσ : DenseRange (StarAlgHom.orbitMap σB η) :=
85    denseRange_source_orbit_of_trace_of_cyclic family σ η hη hσ
86  have hstate (a : Limit) : inner ℂ ξ (ρB a ξ) = inner ℂ η (σB a η) :=
87    (hξ a).trans (hη a).symm
88  obtain ⟨e, he, _⟩ :=
89    StarAlgHom.existsUnique_pointedCyclicTransport ρB σB ξ η hdρ hdσ hstate
90  have hgen (i : MathlibAnnex.CStarAlgebra.PureState.GNSClass Limit) :
91      (e : H →L[ℂ] K).comp (ρ (shellFamilyGenerator family i)) =
92        (σ (shellFamilyGenerator family i)).comp (e : H →L[ℂ] K) := by
93    have hρsum := (stronglyConverges_shell_sums_of_trace_of_cyclic family ρ ξ hξ hρ i).1
94    have hσsum := (stronglyConverges_shell_sums_of_trace_of_cyclic family σ η hη hσ i).1
95    apply ContinuousLinearMap.intertwines_strongLimits (e : H →L[ℂ] K)
96      (e : H →L[ℂ] K) hρsum hσsum
97    exact comp_partialSum_eq_partialSum_comp _ _ _
98      (fun n ↦ he.2.2 ((representativeShellData family i).link n))
99  exact ⟨e, he.2.1,
100    MathlibAnnex.CStarAlgebra.AtomicConstruction.intertwines_of_source_of_generators
101      selectedAtomicRepresentation (shellFamilyLinks family) ρ σ e he.2.2 hgen⟩
102
103end MathlibAnnex.CStarAlgebra.CAR
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