Documentation

Mathlib.MeasureTheory.Function.ConditionalExpectation.CondexpL2

Conditional expectation in L2 #

This file contains one step of the construction of the conditional expectation, which is completed in MeasureTheory.Function.ConditionalExpectation.Basic. See that file for a description of the full process.

We build the conditional expectation of an function, as an element of . This is the orthogonal projection on the subspace of almost everywhere m-measurable functions.

Main definitions #

Implementation notes #

Most of the results in this file are valid for a complete real normed space F. However, some lemmas also use 𝕜 : RCLike:

noncomputable def MeasureTheory.condexpL2 {α : Type u_1} (E : Type u_2) (𝕜 : Type u_7) [RCLike 𝕜] [NormedAddCommGroup E] [InnerProductSpace 𝕜 E] [CompleteSpace E] {m m0 : MeasurableSpace α} {μ : Measure α} (hm : m m0) :
(Lp E 2 μ) →L[𝕜] (lpMeas E 𝕜 m 2 μ)

Conditional expectation of a function in L2 with respect to a sigma-algebra

Equations
Instances For
    theorem MeasureTheory.aeStronglyMeasurable'_condexpL2 {α : Type u_1} {E : Type u_2} {𝕜 : Type u_7} [RCLike 𝕜] [NormedAddCommGroup E] [InnerProductSpace 𝕜 E] [CompleteSpace E] {m m0 : MeasurableSpace α} {μ : Measure α} (hm : m m0) (f : (Lp E 2 μ)) :
    AEStronglyMeasurable' m (↑((condexpL2 E 𝕜 hm) f)) μ
    theorem MeasureTheory.integrableOn_condexpL2_of_measure_ne_top {α : Type u_1} {E : Type u_2} {𝕜 : Type u_7} [RCLike 𝕜] [NormedAddCommGroup E] [InnerProductSpace 𝕜 E] [CompleteSpace E] {m m0 : MeasurableSpace α} {μ : Measure α} {s : Set α} (hm : m m0) (hμs : μ s ) (f : (Lp E 2 μ)) :
    IntegrableOn (↑((condexpL2 E 𝕜 hm) f)) s μ
    theorem MeasureTheory.integrable_condexpL2_of_isFiniteMeasure {α : Type u_1} {E : Type u_2} {𝕜 : Type u_7} [RCLike 𝕜] [NormedAddCommGroup E] [InnerProductSpace 𝕜 E] [CompleteSpace E] {m m0 : MeasurableSpace α} {μ : Measure α} (hm : m m0) [IsFiniteMeasure μ] {f : (Lp E 2 μ)} :
    Integrable (↑((condexpL2 E 𝕜 hm) f)) μ
    theorem MeasureTheory.norm_condexpL2_le_one {α : Type u_1} {E : Type u_2} {𝕜 : Type u_7} [RCLike 𝕜] [NormedAddCommGroup E] [InnerProductSpace 𝕜 E] [CompleteSpace E] {m m0 : MeasurableSpace α} {μ : Measure α} (hm : m m0) :
    condexpL2 E 𝕜 hm 1
    theorem MeasureTheory.norm_condexpL2_le {α : Type u_1} {E : Type u_2} {𝕜 : Type u_7} [RCLike 𝕜] [NormedAddCommGroup E] [InnerProductSpace 𝕜 E] [CompleteSpace E] {m m0 : MeasurableSpace α} {μ : Measure α} (hm : m m0) (f : (Lp E 2 μ)) :
    (condexpL2 E 𝕜 hm) f f
    theorem MeasureTheory.eLpNorm_condexpL2_le {α : Type u_1} {E : Type u_2} {𝕜 : Type u_7} [RCLike 𝕜] [NormedAddCommGroup E] [InnerProductSpace 𝕜 E] [CompleteSpace E] {m m0 : MeasurableSpace α} {μ : Measure α} (hm : m m0) (f : (Lp E 2 μ)) :
    eLpNorm (↑((condexpL2 E 𝕜 hm) f)) 2 μ eLpNorm (↑f) 2 μ
    @[deprecated MeasureTheory.eLpNorm_condexpL2_le (since := "2024-07-27")]
    theorem MeasureTheory.snorm_condexpL2_le {α : Type u_1} {E : Type u_2} {𝕜 : Type u_7} [RCLike 𝕜] [NormedAddCommGroup E] [InnerProductSpace 𝕜 E] [CompleteSpace E] {m m0 : MeasurableSpace α} {μ : Measure α} (hm : m m0) (f : (Lp E 2 μ)) :
    eLpNorm (↑((condexpL2 E 𝕜 hm) f)) 2 μ eLpNorm (↑f) 2 μ

    Alias of MeasureTheory.eLpNorm_condexpL2_le.

    theorem MeasureTheory.norm_condexpL2_coe_le {α : Type u_1} {E : Type u_2} {𝕜 : Type u_7} [RCLike 𝕜] [NormedAddCommGroup E] [InnerProductSpace 𝕜 E] [CompleteSpace E] {m m0 : MeasurableSpace α} {μ : Measure α} (hm : m m0) (f : (Lp E 2 μ)) :
    ((condexpL2 E 𝕜 hm) f) f
    theorem MeasureTheory.inner_condexpL2_left_eq_right {α : Type u_1} {E : Type u_2} {𝕜 : Type u_7} [RCLike 𝕜] [NormedAddCommGroup E] [InnerProductSpace 𝕜 E] [CompleteSpace E] {m m0 : MeasurableSpace α} {μ : Measure α} (hm : m m0) {f g : (Lp E 2 μ)} :
    inner (↑((condexpL2 E 𝕜 hm) f)) g = inner f ((condexpL2 E 𝕜 hm) g)
    theorem MeasureTheory.condexpL2_indicator_of_measurable {α : Type u_1} {E : Type u_2} {𝕜 : Type u_7} [RCLike 𝕜] [NormedAddCommGroup E] [InnerProductSpace 𝕜 E] [CompleteSpace E] {m m0 : MeasurableSpace α} {μ : Measure α} {s : Set α} (hm : m m0) (hs : MeasurableSet s) (hμs : μ s ) (c : E) :
    ((condexpL2 E 𝕜 hm) (indicatorConstLp 2 hμs c)) = indicatorConstLp 2 hμs c
    theorem MeasureTheory.inner_condexpL2_eq_inner_fun {α : Type u_1} {E : Type u_2} {𝕜 : Type u_7} [RCLike 𝕜] [NormedAddCommGroup E] [InnerProductSpace 𝕜 E] [CompleteSpace E] {m m0 : MeasurableSpace α} {μ : Measure α} (hm : m m0) (f g : (Lp E 2 μ)) (hg : AEStronglyMeasurable' m (↑g) μ) :
    inner (↑((condexpL2 E 𝕜 hm) f)) g = inner f g
    theorem MeasureTheory.integral_condexpL2_eq_of_fin_meas_real {α : Type u_1} {𝕜 : Type u_7} [RCLike 𝕜] {m m0 : MeasurableSpace α} {μ : Measure α} {s : Set α} {hm : m m0} (f : (Lp 𝕜 2 μ)) (hs : MeasurableSet s) (hμs : μ s ) :
    (x : α) in s, ((condexpL2 𝕜 𝕜 hm) f) x μ = (x : α) in s, f x μ
    theorem MeasureTheory.lintegral_nnnorm_condexpL2_le {α : Type u_1} {m m0 : MeasurableSpace α} {μ : Measure α} {s : Set α} {hm : m m0} (hs : MeasurableSet s) (hμs : μ s ) (f : (Lp 2 μ)) :
    ∫⁻ (x : α) in s, ((condexpL2 hm) f) x‖₊ μ ∫⁻ (x : α) in s, f x‖₊ μ
    theorem MeasureTheory.condexpL2_ae_eq_zero_of_ae_eq_zero {α : Type u_1} {m m0 : MeasurableSpace α} {μ : Measure α} {s : Set α} {hm : m m0} (hs : MeasurableSet s) (hμs : μ s ) {f : (Lp 2 μ)} (hf : f =ᶠ[ae (μ.restrict s)] 0) :
    ((condexpL2 hm) f) =ᶠ[ae (μ.restrict s)] 0
    theorem MeasureTheory.lintegral_nnnorm_condexpL2_indicator_le_real {α : Type u_1} {m m0 : MeasurableSpace α} {μ : Measure α} {s t : Set α} {hm : m m0} (hs : MeasurableSet s) (hμs : μ s ) (ht : MeasurableSet t) (hμt : μ t ) :
    ∫⁻ (a : α) in t, ((condexpL2 hm) (indicatorConstLp 2 hs hμs 1)) a‖₊ μ μ (s t)
    theorem MeasureTheory.condexpL2_const_inner {α : Type u_1} {E : Type u_2} {𝕜 : Type u_7} [RCLike 𝕜] [NormedAddCommGroup E] [InnerProductSpace 𝕜 E] [CompleteSpace E] {m m0 : MeasurableSpace α} {μ : Measure α} (hm : m m0) (f : (Lp E 2 μ)) (c : E) :
    ((condexpL2 𝕜 𝕜 hm) (Memℒp.toLp (fun (a : α) => inner c (f a)) )) =ᶠ[ae μ] fun (a : α) => inner c (((condexpL2 E 𝕜 hm) f) a)

    condexpL2 commutes with taking inner products with constants. See the lemma condexpL2_comp_continuousLinearMap for a more general result about commuting with continuous linear maps.

    theorem MeasureTheory.integral_condexpL2_eq {α : Type u_1} {E' : Type u_3} {𝕜 : Type u_7} [RCLike 𝕜] [NormedAddCommGroup E'] [InnerProductSpace 𝕜 E'] [CompleteSpace E'] [NormedSpace E'] {m m0 : MeasurableSpace α} {μ : Measure α} {s : Set α} (hm : m m0) (f : (Lp E' 2 μ)) (hs : MeasurableSet s) (hμs : μ s ) :
    (x : α) in s, ((condexpL2 E' 𝕜 hm) f) x μ = (x : α) in s, f x μ

    condexpL2 verifies the equality of integrals defining the conditional expectation.

    theorem MeasureTheory.condexpL2_comp_continuousLinearMap {α : Type u_1} {E' : Type u_3} (𝕜 : Type u_7) [RCLike 𝕜] [NormedAddCommGroup E'] [InnerProductSpace 𝕜 E'] [CompleteSpace E'] [NormedSpace E'] {m m0 : MeasurableSpace α} {μ : Measure α} {E'' : Type u_8} (𝕜' : Type u_9) [RCLike 𝕜'] [NormedAddCommGroup E''] [InnerProductSpace 𝕜' E''] [CompleteSpace E''] [NormedSpace E''] (hm : m m0) (T : E' →L[] E'') (f : (Lp E' 2 μ)) :
    ((condexpL2 E'' 𝕜' hm) (T.compLp f)) =ᶠ[ae μ] (T.compLp ((condexpL2 E' 𝕜 hm) f))
    theorem MeasureTheory.condexpL2_indicator_ae_eq_smul {α : Type u_1} {E' : Type u_3} (𝕜 : Type u_7) [RCLike 𝕜] [NormedAddCommGroup E'] [InnerProductSpace 𝕜 E'] [CompleteSpace E'] [NormedSpace E'] {m m0 : MeasurableSpace α} {μ : Measure α} {s : Set α} (hm : m m0) (hs : MeasurableSet s) (hμs : μ s ) (x : E') :
    ((condexpL2 E' 𝕜 hm) (indicatorConstLp 2 hs hμs x)) =ᶠ[ae μ] fun (a : α) => ((condexpL2 hm) (indicatorConstLp 2 hs hμs 1)) a x
    theorem MeasureTheory.condexpL2_indicator_eq_toSpanSingleton_comp {α : Type u_1} {E' : Type u_3} (𝕜 : Type u_7) [RCLike 𝕜] [NormedAddCommGroup E'] [InnerProductSpace 𝕜 E'] [CompleteSpace E'] [NormedSpace E'] {m m0 : MeasurableSpace α} {μ : Measure α} {s : Set α} (hm : m m0) (hs : MeasurableSet s) (hμs : μ s ) (x : E') :
    ((condexpL2 E' 𝕜 hm) (indicatorConstLp 2 hs hμs x)) = (ContinuousLinearMap.toSpanSingleton x).compLp ((condexpL2 hm) (indicatorConstLp 2 hs hμs 1))
    theorem MeasureTheory.setLIntegral_nnnorm_condexpL2_indicator_le {α : Type u_1} {E' : Type u_3} {𝕜 : Type u_7} [RCLike 𝕜] [NormedAddCommGroup E'] [InnerProductSpace 𝕜 E'] [CompleteSpace E'] [NormedSpace E'] {m m0 : MeasurableSpace α} {μ : Measure α} {s : Set α} (hm : m m0) (hs : MeasurableSet s) (hμs : μ s ) (x : E') {t : Set α} (ht : MeasurableSet t) (hμt : μ t ) :
    ∫⁻ (a : α) in t, ((condexpL2 E' 𝕜 hm) (indicatorConstLp 2 hs hμs x)) a‖₊ μ μ (s t) * x‖₊
    @[deprecated MeasureTheory.setLIntegral_nnnorm_condexpL2_indicator_le (since := "2024-06-29")]
    theorem MeasureTheory.set_lintegral_nnnorm_condexpL2_indicator_le {α : Type u_1} {E' : Type u_3} {𝕜 : Type u_7} [RCLike 𝕜] [NormedAddCommGroup E'] [InnerProductSpace 𝕜 E'] [CompleteSpace E'] [NormedSpace E'] {m m0 : MeasurableSpace α} {μ : Measure α} {s : Set α} (hm : m m0) (hs : MeasurableSet s) (hμs : μ s ) (x : E') {t : Set α} (ht : MeasurableSet t) (hμt : μ t ) :
    ∫⁻ (a : α) in t, ((condexpL2 E' 𝕜 hm) (indicatorConstLp 2 hs hμs x)) a‖₊ μ μ (s t) * x‖₊

    Alias of MeasureTheory.setLIntegral_nnnorm_condexpL2_indicator_le.

    theorem MeasureTheory.lintegral_nnnorm_condexpL2_indicator_le {α : Type u_1} {E' : Type u_3} {𝕜 : Type u_7} [RCLike 𝕜] [NormedAddCommGroup E'] [InnerProductSpace 𝕜 E'] [CompleteSpace E'] [NormedSpace E'] {m m0 : MeasurableSpace α} {μ : Measure α} {s : Set α} (hm : m m0) (hs : MeasurableSet s) (hμs : μ s ) (x : E') [SigmaFinite (μ.trim hm)] :
    ∫⁻ (a : α), ((condexpL2 E' 𝕜 hm) (indicatorConstLp 2 hs hμs x)) a‖₊ μ μ s * x‖₊
    theorem MeasureTheory.integrable_condexpL2_indicator {α : Type u_1} {E' : Type u_3} {𝕜 : Type u_7} [RCLike 𝕜] [NormedAddCommGroup E'] [InnerProductSpace 𝕜 E'] [CompleteSpace E'] [NormedSpace E'] {m m0 : MeasurableSpace α} {μ : Measure α} {s : Set α} (hm : m m0) [SigmaFinite (μ.trim hm)] (hs : MeasurableSet s) (hμs : μ s ) (x : E') :
    Integrable (↑((condexpL2 E' 𝕜 hm) (indicatorConstLp 2 hs hμs x))) μ

    If the measure μ.trim hm is sigma-finite, then the conditional expectation of a measurable set with finite measure is integrable.

    noncomputable def MeasureTheory.condexpIndSMul {α : Type u_1} {G : Type u_5} [NormedAddCommGroup G] {m m0 : MeasurableSpace α} {μ : Measure α} {s : Set α} [NormedSpace G] (hm : m m0) (hs : MeasurableSet s) (hμs : μ s ) (x : G) :
    (Lp G 2 μ)

    Conditional expectation of the indicator of a measurable set with finite measure, in L2.

    Equations
    • One or more equations did not get rendered due to their size.
    Instances For
      theorem MeasureTheory.aeStronglyMeasurable'_condexpIndSMul {α : Type u_1} {G : Type u_5} [NormedAddCommGroup G] {m m0 : MeasurableSpace α} {μ : Measure α} {s : Set α} [NormedSpace G] (hm : m m0) (hs : MeasurableSet s) (hμs : μ s ) (x : G) :
      AEStronglyMeasurable' m (↑(condexpIndSMul hm hs hμs x)) μ
      theorem MeasureTheory.condexpIndSMul_add {α : Type u_1} {G : Type u_5} [NormedAddCommGroup G] {m m0 : MeasurableSpace α} {μ : Measure α} {s : Set α} [NormedSpace G] {hm : m m0} (hs : MeasurableSet s) (hμs : μ s ) (x y : G) :
      condexpIndSMul hm hs hμs (x + y) = condexpIndSMul hm hs hμs x + condexpIndSMul hm hs hμs y
      theorem MeasureTheory.condexpIndSMul_smul {α : Type u_1} {G : Type u_5} [NormedAddCommGroup G] {m m0 : MeasurableSpace α} {μ : Measure α} {s : Set α} [NormedSpace G] {hm : m m0} (hs : MeasurableSet s) (hμs : μ s ) (c : ) (x : G) :
      condexpIndSMul hm hs hμs (c x) = c condexpIndSMul hm hs hμs x
      theorem MeasureTheory.condexpIndSMul_smul' {α : Type u_1} {F : Type u_4} {𝕜 : Type u_7} [RCLike 𝕜] [NormedAddCommGroup F] [NormedSpace 𝕜 F] {m m0 : MeasurableSpace α} {μ : Measure α} {s : Set α} {hm : m m0} [NormedSpace F] [SMulCommClass 𝕜 F] (hs : MeasurableSet s) (hμs : μ s ) (c : 𝕜) (x : F) :
      condexpIndSMul hm hs hμs (c x) = c condexpIndSMul hm hs hμs x
      theorem MeasureTheory.condexpIndSMul_ae_eq_smul {α : Type u_1} {G : Type u_5} [NormedAddCommGroup G] {m m0 : MeasurableSpace α} {μ : Measure α} {s : Set α} [NormedSpace G] (hm : m m0) (hs : MeasurableSet s) (hμs : μ s ) (x : G) :
      (condexpIndSMul hm hs hμs x) =ᶠ[ae μ] fun (a : α) => ((condexpL2 hm) (indicatorConstLp 2 hs hμs 1)) a x
      theorem MeasureTheory.setLIntegral_nnnorm_condexpIndSMul_le {α : Type u_1} {G : Type u_5} [NormedAddCommGroup G] {m m0 : MeasurableSpace α} {μ : Measure α} {s : Set α} [NormedSpace G] (hm : m m0) (hs : MeasurableSet s) (hμs : μ s ) (x : G) {t : Set α} (ht : MeasurableSet t) (hμt : μ t ) :
      ∫⁻ (a : α) in t, (condexpIndSMul hm hs hμs x) a‖₊ μ μ (s t) * x‖₊
      @[deprecated MeasureTheory.setLIntegral_nnnorm_condexpIndSMul_le (since := "2024-06-29")]
      theorem MeasureTheory.set_lintegral_nnnorm_condexpIndSMul_le {α : Type u_1} {G : Type u_5} [NormedAddCommGroup G] {m m0 : MeasurableSpace α} {μ : Measure α} {s : Set α} [NormedSpace G] (hm : m m0) (hs : MeasurableSet s) (hμs : μ s ) (x : G) {t : Set α} (ht : MeasurableSet t) (hμt : μ t ) :
      ∫⁻ (a : α) in t, (condexpIndSMul hm hs hμs x) a‖₊ μ μ (s t) * x‖₊

      Alias of MeasureTheory.setLIntegral_nnnorm_condexpIndSMul_le.

      theorem MeasureTheory.lintegral_nnnorm_condexpIndSMul_le {α : Type u_1} {G : Type u_5} [NormedAddCommGroup G] {m m0 : MeasurableSpace α} {μ : Measure α} {s : Set α} [NormedSpace G] (hm : m m0) (hs : MeasurableSet s) (hμs : μ s ) (x : G) [SigmaFinite (μ.trim hm)] :
      ∫⁻ (a : α), (condexpIndSMul hm hs hμs x) a‖₊ μ μ s * x‖₊
      theorem MeasureTheory.integrable_condexpIndSMul {α : Type u_1} {G : Type u_5} [NormedAddCommGroup G] {m m0 : MeasurableSpace α} {μ : Measure α} {s : Set α} [NormedSpace G] (hm : m m0) [SigmaFinite (μ.trim hm)] (hs : MeasurableSet s) (hμs : μ s ) (x : G) :
      Integrable (↑(condexpIndSMul hm hs hμs x)) μ

      If the measure μ.trim hm is sigma-finite, then the conditional expectation of a measurable set with finite measure is integrable.

      theorem MeasureTheory.condexpIndSMul_empty {α : Type u_1} {G : Type u_5} [NormedAddCommGroup G] {m m0 : MeasurableSpace α} {μ : Measure α} [NormedSpace G] {hm : m m0} {x : G} :
      condexpIndSMul hm x = 0
      theorem MeasureTheory.setIntegral_condexpL2_indicator {α : Type u_1} {m m0 : MeasurableSpace α} {μ : Measure α} {s t : Set α} {hm : m m0} (hs : MeasurableSet s) (ht : MeasurableSet t) (hμs : μ s ) (hμt : μ t ) :
      (x : α) in s, ((condexpL2 hm) (indicatorConstLp 2 ht hμt 1)) x μ = (μ (t s)).toReal
      @[deprecated MeasureTheory.setIntegral_condexpL2_indicator (since := "2024-04-17")]
      theorem MeasureTheory.set_integral_condexpL2_indicator {α : Type u_1} {m m0 : MeasurableSpace α} {μ : Measure α} {s t : Set α} {hm : m m0} (hs : MeasurableSet s) (ht : MeasurableSet t) (hμs : μ s ) (hμt : μ t ) :
      (x : α) in s, ((condexpL2 hm) (indicatorConstLp 2 ht hμt 1)) x μ = (μ (t s)).toReal

      Alias of MeasureTheory.setIntegral_condexpL2_indicator.

      theorem MeasureTheory.setIntegral_condexpIndSMul {α : Type u_1} {G' : Type u_6} [NormedAddCommGroup G'] [NormedSpace G'] [CompleteSpace G'] {m m0 : MeasurableSpace α} {μ : Measure α} {s t : Set α} {hm : m m0} (hs : MeasurableSet s) (ht : MeasurableSet t) (hμs : μ s ) (hμt : μ t ) (x : G') :
      (a : α) in s, (condexpIndSMul hm ht hμt x) a μ = (μ (t s)).toReal x
      @[deprecated MeasureTheory.setIntegral_condexpIndSMul (since := "2024-04-17")]
      theorem MeasureTheory.set_integral_condexpIndSMul {α : Type u_1} {G' : Type u_6} [NormedAddCommGroup G'] [NormedSpace G'] [CompleteSpace G'] {m m0 : MeasurableSpace α} {μ : Measure α} {s t : Set α} {hm : m m0} (hs : MeasurableSet s) (ht : MeasurableSet t) (hμs : μ s ) (hμt : μ t ) (x : G') :
      (a : α) in s, (condexpIndSMul hm ht hμt x) a μ = (μ (t s)).toReal x

      Alias of MeasureTheory.setIntegral_condexpIndSMul.

      theorem MeasureTheory.condexpL2_indicator_nonneg {α : Type u_1} {m m0 : MeasurableSpace α} {μ : Measure α} {s : Set α} (hm : m m0) (hs : MeasurableSet s) (hμs : μ s ) [SigmaFinite (μ.trim hm)] :
      0 ≤ᶠ[ae μ] ((condexpL2 hm) (indicatorConstLp 2 hs hμs 1))
      theorem MeasureTheory.condexpIndSMul_nonneg {α : Type u_1} {m m0 : MeasurableSpace α} {μ : Measure α} {s : Set α} {hm : m m0} {E : Type u_10} [NormedLatticeAddCommGroup E] [NormedSpace E] [OrderedSMul E] [SigmaFinite (μ.trim hm)] (hs : MeasurableSet s) (hμs : μ s ) (x : E) (hx : 0 x) :
      0 ≤ᶠ[ae μ] (condexpIndSMul hm hs hμs x)