Continuous bilinear maps on MeasureTheory.Lp
spaces #
Given a continuous bilinear map B : E →L[𝕜] F →L[𝕜] G
, we define an associated map
ContinuousLinearMap.holder : Lp E p μ → Lp F q μ → Lp G r μ
where p q r
are a Hölder triple.
We bundle this into a bilinear map ContinuousLinearMap.holderₗ
and a continuous
bilinear map ContinuousLinearMap.holderL
under some additional assumptions.
We also declare a heterogeneous scalar multiplication (HSMul
) instance on MeasureTheory.Lp
spaces. Although this could use the ContinuousLinearMap.holder
construction above, we opt not to
do so in order to minimize the necessary type class assumptions.
When p q : ℝ≥0∞
are Hölder conjugate (i.e., HolderConjugate p q
), we also construct the
natural map ContinuousLinearMap.lpPairing : Lp E p μ →L[𝕜] Lp F q μ →L[𝕜] G
given by
fun f g ↦ ∫ x, B (f x) (g x) ∂μ
. When B := (NormedSpace.inclusionInDoubleDual 𝕜 E).flip
, this
is the natural map Lp (Dual 𝕜 E) p μ →L[𝕜] Dual 𝕜 (Lp E q μ)
.
Induced bilinear maps #
The map between MeasuryTheory.Lp
spaces satisfying ENNReal.HolderTriple
induced by a continuous bilinear map on the underlying spaces.
Equations
- ContinuousLinearMap.holder r B f g = MeasureTheory.MemLp.toLp (fun (x : α) => (B (↑↑f x)) (↑↑g x)) ⋯
Instances For
MeasureTheory.Lp.holder
as a bilinear map.
Equations
- ContinuousLinearMap.holderₗ μ p q r B = LinearMap.mk₂ 𝕜 (ContinuousLinearMap.holder r B) ⋯ ⋯ ⋯ ⋯
Instances For
MeasureTheory.Lp.holder
as a continuous bilinear map.
Equations
- ContinuousLinearMap.holderL μ p q r B = (ContinuousLinearMap.holderₗ μ p q r B).mkContinuous₂ ‖B‖ ⋯
Instances For
The natural pairing between Lp E p μ
and Lp F q μ
(for Hölder conjugate p q : ℝ≥0∞
) with
values in a space G
induced by a bilinear map B : E →L[𝕜] F →L[𝕜] G
.
This is given by ∫ x, B (f x) (g x) ∂μ
.
In the special case when B := (NormedSpace.inclusionInDoubleDual 𝕜 E).flip
, which is
definitionally the same as B := ContinuousLinearMap.id 𝕜 (E →L[𝕜] 𝕜)
, this is the
natural map Lp (Dual 𝕜 E) p μ →L[𝕜] Dual 𝕜 (Lp E q μ)
.
Equations
- ContinuousLinearMap.lpPairing μ p q B = (ContinuousLinearMap.postcomp (↥(MeasureTheory.Lp F q μ)) (MeasureTheory.L1.integralCLM' 𝕜)).comp (ContinuousLinearMap.holderL μ p q 1 B)
Instances For
Heterogeneous scalar multiplication #
While the previous section is nominally more general than this one, and indeed, we could
use the constructions of the previous section to define the scalar multiplication herein,
we would lose some slight generality as we would need to require that 𝕜
is a nontrivially
normed field everywhere. Moreover, it would only simplify a few proofs.
Heterogeneous scalar multiplication of MeasureTheory.Lp
functions by MeasureTheory.Lp
functions when the exponents satisfy ENNReal.HolderTriple p q r
.
Equations
- MeasureTheory.Lp.instHSMulSubtypeAEEqFunMemAddSubgroup = { hSMul := fun (f : ↥(MeasureTheory.Lp 𝕜 p μ)) (g : ↥(MeasureTheory.Lp E q μ)) => MeasureTheory.MemLp.toLp (↑↑f • ↑↑g) ⋯ }