Documentation

TauCeti.Analysis.OperatorIdeal.Carrier

Operator gauges and their normed carriers #

An operator gauge g : OperatorGauge 𝕜 E F assigns an extended value g A ∈ [0, ∞] to every bounded operator A : E →L[𝕜] F between normed spaces. It is subadditive, absolutely homogeneous, and dominates the operator norm. Examples are the Schatten and Ky Fan gauges on Hilbert spaces, and the nuclear and absolutely summing gauges on Banach spaces; the operator-ideal families of TauCeti.Analysis.OperatorIdeal.Family restrict to operator gauges on each pair of Hilbert spaces.

The operators of finite gauge form the submodule g.finiteSubmodule of E →L[𝕜] F. The finite real value of the gauge is a norm on it, in general finer than the operator norm. Since that norm differs from the operator norm, the finite-gauge operators are packaged as a separate type g.Carrier rather than as the subtype of g.finiteSubmodule, which would inherit the operator norm.

When F is a normed space, the carrier g.Carrier is a normed space over 𝕜 with ‖T‖ = (g T).toReal. No information is lost in passing to the real norm, since ‖T‖ₑ = g T, and the inclusion into bounded operators is a contraction. If moreover F is complete and the gauge is lower semicontinuous for the operator-norm topology, then the carrier is a Banach space: a Cauchy sequence for the gauge norm is Cauchy for the operator norm, and lower semicontinuity bounds the gauge of the distance to its operator-norm limit.

Main declarations #

References #

structure TauCeti.OperatorGauge (𝕜 : Type u_1) (E : Type u_2) (F : Type u_3) [NontriviallyNormedField 𝕜] [SeminormedAddCommGroup E] [NormedSpace 𝕜 E] [SeminormedAddCommGroup F] [NormedSpace 𝕜 F] :
Type (max u_2 u_3)

An operator gauge on E →L[𝕜] F: an extended nonnegative function on bounded operators that is subadditive, absolutely homogeneous and dominates the operator norm.

Instances For
    theorem TauCeti.OperatorGauge.ext {𝕜 : Type u_1} {E : Type u_2} {F : Type u_3} [NontriviallyNormedField 𝕜] [SeminormedAddCommGroup E] [NormedSpace 𝕜 E] [SeminormedAddCommGroup F] [NormedSpace 𝕜 F] {g h : OperatorGauge 𝕜 E F} (H : ∀ (A : E →L[𝕜] F), g A = h A) :
    g = h
    theorem TauCeti.OperatorGauge.ext_iff {𝕜 : Type u_1} {E : Type u_2} {F : Type u_3} [NontriviallyNormedField 𝕜] [SeminormedAddCommGroup E] [NormedSpace 𝕜 E] [SeminormedAddCommGroup F] [NormedSpace 𝕜 F] {g h : OperatorGauge 𝕜 E F} :
    g = h ↔ ∀ (A : E →L[𝕜] F), g A = h A
    @[simp]
    theorem TauCeti.OperatorGauge.coe_mk {𝕜 : Type u_1} {E : Type u_2} {F : Type u_3} [NontriviallyNormedField 𝕜] [SeminormedAddCommGroup E] [NormedSpace 𝕜 E] [SeminormedAddCommGroup F] [NormedSpace 𝕜 F] (f : (E →L[𝕜] F) → ENNReal) (h₁ : ∀ (A B : E →L[𝕜] F), f (A + B) ≤ f A + f B) (h₂ : ∀ (c : 𝕜) (A : E →L[𝕜] F), f (c • A) = ‖c‖ₑ * f A) (h₃ : ∀ (A : E →L[𝕜] F), ‖A‖ₑ ≤ f A) :
    ⇑{ toFun := f, map_add_le' := h₁, map_smul' := h₂, enorm_le' := h₃ } = f
    @[simp]
    theorem TauCeti.OperatorGauge.toFun_eq_coe {𝕜 : Type u_1} {E : Type u_2} {F : Type u_3} [NontriviallyNormedField 𝕜] [SeminormedAddCommGroup E] [NormedSpace 𝕜 E] [SeminormedAddCommGroup F] [NormedSpace 𝕜 F] (g : OperatorGauge 𝕜 E F) :
    g.toFun = ⇑g
    theorem TauCeti.OperatorGauge.map_add_le {𝕜 : Type u_1} {E : Type u_2} {F : Type u_3} [NontriviallyNormedField 𝕜] [SeminormedAddCommGroup E] [NormedSpace 𝕜 E] [SeminormedAddCommGroup F] [NormedSpace 𝕜 F] (g : OperatorGauge 𝕜 E F) (A B : E →L[𝕜] F) :
    g (A + B) ≤ g A + g B

    An operator gauge is subadditive.

    @[simp]
    theorem TauCeti.OperatorGauge.map_smul {𝕜 : Type u_1} {E : Type u_2} {F : Type u_3} [NontriviallyNormedField 𝕜] [SeminormedAddCommGroup E] [NormedSpace 𝕜 E] [SeminormedAddCommGroup F] [NormedSpace 𝕜 F] (g : OperatorGauge 𝕜 E F) (c : 𝕜) (A : E →L[𝕜] F) :
    g (c • A) = ‖c‖ₑ * g A

    An operator gauge is absolutely homogeneous.

    theorem TauCeti.OperatorGauge.enorm_le {𝕜 : Type u_1} {E : Type u_2} {F : Type u_3} [NontriviallyNormedField 𝕜] [SeminormedAddCommGroup E] [NormedSpace 𝕜 E] [SeminormedAddCommGroup F] [NormedSpace 𝕜 F] (g : OperatorGauge 𝕜 E F) (A : E →L[𝕜] F) :

    An operator gauge dominates the extended operator norm.

    @[simp]
    theorem TauCeti.OperatorGauge.map_zero {𝕜 : Type u_1} {E : Type u_2} {F : Type u_3} [NontriviallyNormedField 𝕜] [SeminormedAddCommGroup E] [NormedSpace 𝕜 E] [SeminormedAddCommGroup F] [NormedSpace 𝕜 F] (g : OperatorGauge 𝕜 E F) :
    g 0 = 0
    @[simp]
    theorem TauCeti.OperatorGauge.map_neg {𝕜 : Type u_1} {E : Type u_2} {F : Type u_3} [NontriviallyNormedField 𝕜] [SeminormedAddCommGroup E] [NormedSpace 𝕜 E] [SeminormedAddCommGroup F] [NormedSpace 𝕜 F] (g : OperatorGauge 𝕜 E F) (A : E →L[𝕜] F) :
    g (-A) = g A
    @[simp]
    theorem TauCeti.OperatorGauge.map_eq_zero_iff {𝕜 : Type u_1} {E : Type u_2} [NontriviallyNormedField 𝕜] [SeminormedAddCommGroup E] [NormedSpace 𝕜 E] {F : Type u_4} [NormedAddCommGroup F] [NormedSpace 𝕜 F] (g : OperatorGauge 𝕜 E F) {A : E →L[𝕜] F} :
    g A = 0 ↔ A = 0

    An operator gauge into a normed space vanishes exactly at zero.

    The submodule of operators of finite gauge #

    def TauCeti.OperatorGauge.finiteSubmodule {𝕜 : Type u_1} {E : Type u_2} {F : Type u_3} [NontriviallyNormedField 𝕜] [SeminormedAddCommGroup E] [NormedSpace 𝕜 E] [SeminormedAddCommGroup F] [NormedSpace 𝕜 F] (g : OperatorGauge 𝕜 E F) :
    Submodule 𝕜 (E →L[𝕜] F)

    The operators of finite gauge form a submodule of the bounded operators.

    Instances For
      @[simp]
      theorem TauCeti.OperatorGauge.mem_finiteSubmodule {𝕜 : Type u_1} {E : Type u_2} {F : Type u_3} [NontriviallyNormedField 𝕜] [SeminormedAddCommGroup E] [NormedSpace 𝕜 E] [SeminormedAddCommGroup F] [NormedSpace 𝕜 F] {g : OperatorGauge 𝕜 E F} {A : E →L[𝕜] F} :

      The normed carrier #

      structure TauCeti.OperatorGauge.Carrier {𝕜 : Type u_1} {E : Type u_2} {F : Type u_3} [NontriviallyNormedField 𝕜] [SeminormedAddCommGroup E] [NormedSpace 𝕜 E] [SeminormedAddCommGroup F] [NormedSpace 𝕜 F] (g : OperatorGauge 𝕜 E F) :
      Type (max u_2 u_3)

      The operators of finite gauge, normed by the finite real value of the gauge.

      This is a separate type from the subtype of g.finiteSubmodule, which carries the operator norm.

      Instances For
        theorem TauCeti.OperatorGauge.Carrier.ext {𝕜 : Type u_1} {E : Type u_2} {F : Type u_3} {inst✝ : NontriviallyNormedField 𝕜} {inst✝¹ : SeminormedAddCommGroup E} {inst✝² : NormedSpace 𝕜 E} {inst✝³ : SeminormedAddCommGroup F} {inst✝⁴ : NormedSpace 𝕜 F} {g : OperatorGauge 𝕜 E F} {x y : g.Carrier} (toContinuousLinearMap : x.toContinuousLinearMap = y.toContinuousLinearMap) :
        x = y
        theorem TauCeti.OperatorGauge.Carrier.ext_iff {𝕜 : Type u_1} {E : Type u_2} {F : Type u_3} {inst✝ : NontriviallyNormedField 𝕜} {inst✝¹ : SeminormedAddCommGroup E} {inst✝² : NormedSpace 𝕜 E} {inst✝³ : SeminormedAddCommGroup F} {inst✝⁴ : NormedSpace 𝕜 F} {g : OperatorGauge 𝕜 E F} {x y : g.Carrier} :
        @[simp]

        The underlying operators of the carrier are exactly the operators of finite gauge.

        @[instance_reducible]
        @[instance_reducible]
        @[instance_reducible]
        @[instance_reducible]
        @[instance_reducible]
        instance TauCeti.OperatorGauge.Carrier.instSMulOfIsScalarTowerContinuousLinearMapId {𝕜 : Type u_1} {E : Type u_2} {F : Type u_3} [NontriviallyNormedField 𝕜] [SeminormedAddCommGroup E] [NormedSpace 𝕜 E] [SeminormedAddCommGroup F] [NormedSpace 𝕜 F] {g : OperatorGauge 𝕜 E F} {R : Type u_4} [SMul R 𝕜] [SMul R (E →L[𝕜] F)] [IsScalarTower R 𝕜 (E →L[𝕜] F)] :
        @[simp]
        theorem TauCeti.OperatorGauge.Carrier.toContinuousLinearMap_smul {𝕜 : Type u_1} {E : Type u_2} {F : Type u_3} [NontriviallyNormedField 𝕜] [SeminormedAddCommGroup E] [NormedSpace 𝕜 E] [SeminormedAddCommGroup F] [NormedSpace 𝕜 F] {g : OperatorGauge 𝕜 E F} {R : Type u_4} [SMul R 𝕜] [SMul R (E →L[𝕜] F)] [IsScalarTower R 𝕜 (E →L[𝕜] F)] (c : R) (T : g.Carrier) :
        @[instance_reducible]
        @[instance_reducible]

        The gauge of the underlying operator, as an additive group norm on the carrier.

        Instances For

          The norm of an element of the carrier is the finite real value of its gauge.

          @[simp]

          The extended norm of an element of the carrier is its gauge.

          Passing from the gauge to the real norm of the carrier loses no information.

          @[instance_reducible]

          The operator norm is dominated by the norm of the carrier.

          noncomputable def TauCeti.OperatorGauge.Carrier.toContinuousLinearMapL {𝕜 : Type u_1} {E : Type u_2} [NontriviallyNormedField 𝕜] [SeminormedAddCommGroup E] [NormedSpace 𝕜 E] {F : Type u_4} [NormedAddCommGroup F] [NormedSpace 𝕜 F] (g : OperatorGauge 𝕜 E F) :
          g.Carrier →L[𝕜] E →L[𝕜] F

          The inclusion of the carrier into the bounded operators, as a bounded linear map.

          Instances For

            The inclusion of the carrier into the bounded operators is a contraction.

            Completeness #

            If the target is complete and the gauge is lower semicontinuous for the operator-norm topology, then the carrier is complete.