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MIPRE.Background.Repetition.CommutingRepetition.VN.Haagerup.Reduction

The generating unitaries λ(2^{-n}) #

noncomputable def CommutingRepetition.VN.Haagerup.qn (n : ℕ) :

The rational 2^{-n}.

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    The logarithms a_n #

    a_n = 2^n·(−i log λ(2^{-n})): self-adjoint, in ℛ, and in the centralizer of ψ̂.

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      The exponentials of a_n #

      The perturbed vectors and their modular groups #

      theorem CommutingRepetition.VN.Haagerup.isCyclic_xin {K : Type u_1} [NormedAddCommGroup K] [InnerProductSpace ℂ K] [CompleteSpace K] (M : VonNeumannAlgebra K) (Ω : K) (hs : IsSeparating (↑M) Ω) (hc : IsCyclic (↑M) Ω) (n : ℕ) :
      IsCyclic (↑(Crossed.crossed M Ω)) (xin Ω n)
      theorem CommutingRepetition.VN.Haagerup.σ_xin {K : Type u_1} [NormedAddCommGroup K] [InnerProductSpace ℂ K] [CompleteSpace K] (M : VonNeumannAlgebra K) (Ω : K) (hs : IsSeparating (↑M) Ω) (hc : IsCyclic (↑M) Ω) (n : ℕ) (t : ℝ) {x : Crossed.L2Q K →L[ℂ] Crossed.L2Q K} (hx : x ∈ Crossed.crossed M Ω) :
      Modular.σ (Crossed.crossed M Ω) (xin Ω n) t x = Modular.eit (an n) ⋯ (-t) * Modular.σ (Crossed.crossed M Ω) (Crossed.Ωh Ω) t x * Modular.eit (an n) ⋯ t

      The modular group of ξ_n: σ^{ξ_n}_t = Ad(e^{−ita_n}) ∘ σ̂_t on ℛ.

      theorem CommutingRepetition.VN.Haagerup.σ_xin_period {K : Type u_1} [NormedAddCommGroup K] [InnerProductSpace ℂ K] [CompleteSpace K] (M : VonNeumannAlgebra K) (Ω : K) (hs : IsSeparating (↑M) Ω) (hc : IsCyclic (↑M) Ω) (n : ℕ) {x : Crossed.L2Q K →L[ℂ] Crossed.L2Q K} (hx : x ∈ Crossed.crossed M Ω) :
      Modular.σ (Crossed.crossed M Ω) (xin Ω n) (1 / 2 ^ n) x = x

      Periodicity: σ^{ξ_n} is 2^{-n}-periodic on ℛ, i.e. trivial at t = 2^{-n}.

      The centralizer algebra ℛ_n #

      The centralizer ℛ_n of the perturbed state: the elements of ℛ commuting with R(ℛ, ξ_n), equivalently the fixed points of σ^{ξ_n}.

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        theorem CommutingRepetition.VN.Haagerup.mem_Rn_iff_σ {K : Type u_1} [NormedAddCommGroup K] [InnerProductSpace ℂ K] [CompleteSpace K] (M : VonNeumannAlgebra K) (Ω : K) (hs : IsSeparating (↑M) Ω) (hc : IsCyclic (↑M) Ω) {n : ℕ} {x : Crossed.L2Q K →L[ℂ] Crossed.L2Q K} :
        x ∈ Rn M Ω n ↔ x ∈ Crossed.crossed M Ω ∧ ∀ (t : ℝ), Modular.σ (Crossed.crossed M Ω) (xin Ω n) t x = x

        ℛ_n is exactly the fixed-point algebra of σ^{ξ_n}.

        theorem CommutingRepetition.VN.Haagerup.isClosed_Rn {K : Type u_1} [NormedAddCommGroup K] [InnerProductSpace ℂ K] [CompleteSpace K] (M : VonNeumannAlgebra K) (Ω : K) (hs : IsSeparating (↑M) Ω) (hc : IsCyclic (↑M) Ω) (n : ℕ) :
        IsClosed ↑(Rn M Ω n)

        Traciality and the Radon–Nikodym element #

        theorem CommutingRepetition.VN.Haagerup.tracial_Rn {K : Type u_1} [NormedAddCommGroup K] [InnerProductSpace ℂ K] [CompleteSpace K] (M : VonNeumannAlgebra K) (Ω : K) (hs : IsSeparating (↑M) Ω) (hc : IsCyclic (↑M) Ω) (n : ℕ) {x y : Crossed.L2Q K →L[ℂ] Crossed.L2Q K} (hx : x ∈ Rn M Ω n) (hy : y ∈ Crossed.crossed M Ω) :
        inner ℂ (xin Ω n) ((x * y) (xin Ω n)) = inner ℂ (xin Ω n) ((y * x) (xin Ω n))

        The perturbed state is tracial on ℛ_n (IsCentral.tracial).

        d_n = e^{a_n}, the Radon–Nikodym derivative of ψ̂ with respect to ψ_{ξ_n}.

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          theorem CommutingRepetition.VN.Haagerup.inner_Ωh_eq_inner_xin_dn {K : Type u_1} [NormedAddCommGroup K] [InnerProductSpace ℂ K] [CompleteSpace K] (M : VonNeumannAlgebra K) (Ω : K) (hs : IsSeparating (↑M) Ω) (hc : IsCyclic (↑M) Ω) (n : ℕ) {x : Crossed.L2Q K →L[ℂ] Crossed.L2Q K} (hx : x ∈ Crossed.crossed M Ω) :
          inner ℂ (Crossed.Ωh Ω) (x (Crossed.Ωh Ω)) = inner ℂ (xin Ω n) ((dn n * x) (xin Ω n))

          ψ̂ = ψ_{ξ_n}(d_n ·) on ℛ: the state of Ω̂ is the d_n-perturbation of the state of ξ_n.

          The averaging weight 2^n·1_{(0,2^{-n}]} #

          noncomputable def CommutingRepetition.VN.Haagerup.Tn (n : ℕ) :

          The period T_n = 2^{-n} of σ^{ξ_n}.

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            noncomputable def CommutingRepetition.VN.Haagerup.wtR (n : ℕ) :
            ℝ → ℝ

            The real averaging weight 2^n·1_{(0,2^{-n}]}: a probability density.

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              noncomputable def CommutingRepetition.VN.Haagerup.wt (n : ℕ) (t : ℝ) :

              The averaging weight as a complex-valued function.

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                theorem CommutingRepetition.VN.Haagerup.wtR_of_mem {n : ℕ} {t : ℝ} (h : t ∈ Set.Ioc 0 (Tn n)) :
                wtR n t = 2 ^ n
                theorem CommutingRepetition.VN.Haagerup.wtR_of_notMem {n : ℕ} {t : ℝ} (h : t ∉ Set.Ioc 0 (Tn n)) :
                wtR n t = 0
                theorem CommutingRepetition.VN.Haagerup.wt_eq_indicator (n : ℕ) :
                wt n = (Set.Ioc 0 (Tn n)).indicator fun (x : ℝ) => ↑(2 ^ n)
                theorem CommutingRepetition.VN.Haagerup.integral_wt_smul {E : Type u_2} [NormedAddCommGroup E] [NormedSpace ℂ E] (n : ℕ) (g : ℝ → E) :
                ∫ (t : ℝ), wt n t • g t = ↑(2 ^ n) • ∫ (t : ℝ) in 0..Tn n, g t

                Integrating against wt n is averaging over one period.

                The conditional expectation Φ_n #

                Haagerup's conditional expectation Φ_n(x) = 2^n ∫_0^{2^{-n}} σ^{ξ_n}_t(x) dt, realized as a weak (vectorwise) integral.

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                  theorem CommutingRepetition.VN.Haagerup.Phi_apply {K : Type u_1} [NormedAddCommGroup K] [InnerProductSpace ℂ K] [CompleteSpace K] (M : VonNeumannAlgebra K) (Ω : K) (n : ℕ) (x : Crossed.L2Q K →L[ℂ] Crossed.L2Q K) (ζ : Crossed.L2Q K) :
                  (Phi M Ω n x) ζ = ↑(2 ^ n) • ∫ (t : ℝ) in 0..Tn n, (Modular.σ (Crossed.crossed M Ω) (xin Ω n) t x) ζ
                  theorem CommutingRepetition.VN.Haagerup.Phi_mem {K : Type u_1} [NormedAddCommGroup K] [InnerProductSpace ℂ K] [CompleteSpace K] (M : VonNeumannAlgebra K) (Ω : K) (hs : IsSeparating (↑M) Ω) (hc : IsCyclic (↑M) Ω) (n : ℕ) {x : Crossed.L2Q K →L[ℂ] Crossed.L2Q K} (hx : x ∈ Crossed.crossed M Ω) :
                  Phi M Ω n x ∈ Crossed.crossed M Ω

                  Φ_n maps ℛ into ℛ.

                  Φ_n is unital.

                  theorem CommutingRepetition.VN.Haagerup.Phi_add {K : Type u_1} [NormedAddCommGroup K] [InnerProductSpace ℂ K] [CompleteSpace K] (M : VonNeumannAlgebra K) (Ω : K) (n : ℕ) (x y : Crossed.L2Q K →L[ℂ] Crossed.L2Q K) :
                  Phi M Ω n (x + y) = Phi M Ω n x + Phi M Ω n y

                  Φ_n lands in ℛ_n #

                  theorem CommutingRepetition.VN.Haagerup.periodic_σ_xin {K : Type u_1} [NormedAddCommGroup K] [InnerProductSpace ℂ K] [CompleteSpace K] (M : VonNeumannAlgebra K) (Ω : K) (hs : IsSeparating (↑M) Ω) (hc : IsCyclic (↑M) Ω) (n : ℕ) {x : Crossed.L2Q K →L[ℂ] Crossed.L2Q K} (hx : x ∈ Crossed.crossed M Ω) (ζ : Crossed.L2Q K) :
                  Function.Periodic (fun (t : ℝ) => (Modular.σ (Crossed.crossed M Ω) (xin Ω n) t x) ζ) (Tn n)
                  theorem CommutingRepetition.VN.Haagerup.σ_Phi {K : Type u_1} [NormedAddCommGroup K] [InnerProductSpace ℂ K] [CompleteSpace K] (M : VonNeumannAlgebra K) (Ω : K) (hs : IsSeparating (↑M) Ω) (hc : IsCyclic (↑M) Ω) (n : ℕ) (s : ℝ) {x : Crossed.L2Q K →L[ℂ] Crossed.L2Q K} (hx : x ∈ Crossed.crossed M Ω) :
                  Modular.σ (Crossed.crossed M Ω) (xin Ω n) s (Phi M Ω n x) = Phi M Ω n x

                  σ^{ξ_n} fixes the range of Φ_n: the average over one full period is invariant.

                  theorem CommutingRepetition.VN.Haagerup.Phi_mem_Rn {K : Type u_1} [NormedAddCommGroup K] [InnerProductSpace ℂ K] [CompleteSpace K] (M : VonNeumannAlgebra K) (Ω : K) (hs : IsSeparating (↑M) Ω) (hc : IsCyclic (↑M) Ω) (n : ℕ) {x : Crossed.L2Q K →L[ℂ] Crossed.L2Q K} (hx : x ∈ Crossed.crossed M Ω) :
                  Phi M Ω n x ∈ Rn M Ω n

                  Φ_n maps ℛ into the centralizer ℛ_n.

                  Φ_n is the identity on ℛ_n, so it is a projection onto ℛ_n.

                  Φ_n preserves the state, positivity and self-adjointness #

                  theorem CommutingRepetition.VN.Haagerup.inner_xin_Phi {K : Type u_1} [NormedAddCommGroup K] [InnerProductSpace ℂ K] [CompleteSpace K] (M : VonNeumannAlgebra K) (Ω : K) (n : ℕ) (x : Crossed.L2Q K →L[ℂ] Crossed.L2Q K) :
                  inner ℂ (xin Ω n) ((Phi M Ω n x) (xin Ω n)) = inner ℂ (xin Ω n) (x (xin Ω n))

                  ψ_{ξ_n} ∘ Φ_n = ψ_{ξ_n}.

                  Φ_n is positive.