The estimate for on the cylinder , up to a lower-order term
ProvedCauchyRiemannIndex.periodic_cauchyRiemann_estimateLet and , and let . There is a constant such that every continuously differentiable map which is -periodic in the second variable, , and vanishes for large satisfies
where all norms are taken over the cylinder , i.e. over the strip with Lebesgue measure.
It is the estimate for the standard Cauchy–Riemann operator on the cylinder, the case of the local estimate for Cauchy–Riemann type operators (Wendl, Proposition 4.8). The constant does not depend on the size of the support of .
Formalization Note. is EuclideanSpace ℝ (Fin n ⊕ Fin n), is Matrix.J, acting through Matrix.toEuclideanLin. Points of the plane are pairs ; and are partialS v x = fderiv ℝ v x (1, 0) and partialT v x = fderiv ℝ v x (0, 1). means ContDiff ℝ 1. Norms are eLpNorm with values in , for an exponent p : ℝ≥0∞ with and . Lebesgue measure on the strip is cylMeasure. Vanishing for large means: there is with whenever . The constant is chosen before (and before ).
import Definitions.Def_CauchyRiemannIndex_Setting import Mathlib.Analysis.Calculus.ContDiff.Basic
namespace CauchyRiemannIndex
open MeasureTheory Matrix
open scoped ENNReal NNReal
/-- For `1 < p < ∞` there is `A` such that every `C¹` map `u : ℝ × ℝ → ℝ²ⁿ` that is `1`-periodic
in `t` and vanishes for large `|s|` satisfies, on the cylinder `ℝ × S¹`,
`‖∂ₛu‖_p + ‖∂ₜu‖_p ≤ A ‖∂ₛu + J₀ ∂ₜu‖_p + A ‖u‖_p`. -/
theorem periodic_cauchyRiemann_estimate (n : ℕ) (p : ℝ≥0∞) (hp : 1 < p) (hp' : p ≠ ⊤) :
∃ A : ℝ≥0, ∀ u : ℝ × ℝ → Vec n, ContDiff ℝ 1 u → (∀ s t, u (s, t + 1) = u (s, t)) →
(∃ R : ℝ, ∀ s t, R < |s| → u (s, t) = 0) →
eLpNorm (partialS u) p cylMeasure + eLpNorm (partialT u) p cylMeasure ≤
A * eLpNorm (fun x => partialS u x + Matrix.toEuclideanLin (J₀ n) (partialT u x)) p
cylMeasure + A * eLpNorm u p cylMeasure := by
sorry
end CauchyRiemannIndex