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The LpL^pLp estimate for ∂s+J0∂t\partial_s+J_0\partial_t∂s​+J0​∂t​ on the cylinder R×S1\mathbb R\times S^1R×S1, up to a lower-order term

Proved
CauchyRiemannIndex.periodic_cauchyRiemann_estimate

by Mazecto · Oct 15, 2026 · Mathlib 0df444a (Lean v4.33.1)

cauchy-riemannelliptic-estimatessymplectic-geometry

Let 1<p<∞1<p<\infty1<p<∞ and n∈Nn\in\mathbb Nn∈N, and let J0=(0−IdId0)J_0=\begin{pmatrix}0&-\mathrm{Id}\\ \mathrm{Id}&0\end{pmatrix}J0​=(0Id​−Id0​). There is a constant AAA such that every continuously differentiable map u:R×R→R2nu:\mathbb R\times\mathbb R\to\mathbb R^{2n}u:R×R→R2n which is 111-periodic in the second variable, u(s,t+1)=u(s,t)u(s,t+1)=u(s,t)u(s,t+1)=u(s,t), and vanishes for ∣s∣|s|∣s∣ large satisfies

∥∂su∥Lp+∥∂tu∥Lp≤A ∥∂su+J0 ∂tu∥Lp+A ∥u∥Lp,\|\partial_s u\|_{L^p}+\|\partial_t u\|_{L^p}\le A\,\|\partial_s u+J_0\,\partial_t u\|_{L^p}+A\,\|u\|_{L^p},∥∂s​u∥Lp​+∥∂t​u∥Lp​≤A∥∂s​u+J0​∂t​u∥Lp​+A∥u∥Lp​,

where all norms are taken over the cylinder R×S1\mathbb R\times S^1R×S1, i.e. over the strip R×[0,1)\mathbb R\times[0,1)R×[0,1) with Lebesgue measure.

It is the LpL^pLp estimate for the standard Cauchy–Riemann operator on the cylinder, the case S=0S=0S=0 of the local estimate for Cauchy–Riemann type operators ∂s+J0∂t+S\partial_s+J_0\partial_t+S∂s​+J0​∂t​+S (Wendl, Proposition 4.8). The constant does not depend on the size of the support of uuu.

Formalization Note. R2n\mathbb R^{2n}R2n is EuclideanSpace ℝ (Fin n ⊕ Fin n), J0J_0J0​ is Matrix.J, acting through Matrix.toEuclideanLin. Points of the plane are pairs (s,t)∈R×R(s,t)\in\mathbb R\times\mathbb R(s,t)∈R×R; ∂sv\partial_s v∂s​v and ∂tv\partial_t v∂t​v are partialS v x = fderiv ℝ v x (1, 0) and partialT v x = fderiv ℝ v x (0, 1). C1C^1C1 means ContDiff ℝ 1. Norms are eLpNorm with values in [0,∞][0,\infty][0,∞], for an exponent p : ℝ≥0∞ with 1<p1<p1<p and p≠∞p\ne\inftyp=∞. Lebesgue measure on the strip is cylMeasure. Vanishing for large ∣s∣|s|∣s∣ means: there is RRR with u(s,t)=0u(s,t)=0u(s,t)=0 whenever R<∣s∣R<|s|R<∣s∣. The constant AAA is chosen before uuu (and before RRR).

Preamble
import Definitions.Def_CauchyRiemannIndex_Setting
import Mathlib.Analysis.Calculus.ContDiff.Basic
Formal statement
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
Source
C. Wendl, Lectures on Symplectic Field Theory, arXiv:1612.01009, https://arxiv.org/abs/1612.01009, Lecture 4, Proposition 4.8, p. 71 (local estimate for Cauchy–Riemann type operators)

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