Sewing with a constant-scaled control #
The additive sewing lemma packaged for germs whose defect is bounded by
C·ω^θ: the scaling constant is absorbed into the control, so all three
rough-integral constructions (word, branched, planarly branched) reduce
to one application.
theorem
RoughPaths.Sewing.sewing_const_mul
{T : Type u_1}
[LinearOrder T]
{E : Type u_2}
[NormedAddCommGroup E]
[CompleteSpace E]
(ω : Control T)
(Ξ : T → T → E)
{θ : ℝ}
{C : ENNReal}
(hθ : 1 < θ)
(hθ0 : θ ≠ 0)
(hC : C ≠ ⊤)
(hδ : ∀ ⦃a b c : T⦄, a ≤ b → b ≤ c → ‖Ξ a c - Ξ a b - Ξ b c‖ₑ ≤ C * ω.toFun a c ^ θ)
(hfine : HasFinePartitions ω)
(hω : ∀ ⦃s t : T⦄, s ≤ t → ω.toFun s t ≠ ⊤)
:
∃ (I : T → T → E),
(∀ ⦃s u t : T⦄, s ≤ u → u ≤ t → I s u + I u t = I s t) ∧ (∀ ⦃s t : T⦄, s ≤ t → ‖I s t - Ξ s t‖ₑ ≤ sewingConst θ * (C * ω.toFun s t ^ θ)) ∧ ∀ ⦃s t : T⦄,
s ≤ t →
∀ (ε : ENNReal) (mid : List T),
List.IsChain (fun (a b : T) => a ≤ b ∧ (Control.constMul (C ^ θ⁻¹) ω).toFun a b ≤ ε) (s :: (mid ++ [t])) →
‖I s t - pairSum Ξ (s :: (mid ++ [t]))‖ₑ ≤ sewingConst θ * (ε ^ (θ - 1) * (Control.constMul (C ^ θ⁻¹) ω).toFun s t)
Scaled sewing: a germ with defect bound C·ω^θ, θ > 1, sews
into an additive primitive with the correspondingly scaled estimates.