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arxiv: 2605.15590 · v1 · pith:UUWNHMJPnew · submitted 2026-05-15 · 🧮 math.CA · math-ph· math.MP· nlin.PS

Generalized Error Bounds in the Recovery of Solitary Wave Profiles

Pith reviewed 2026-05-19 18:39 UTC · model grok-4.3

classification 🧮 math.CA math-phmath.MPnlin.PS
keywords solitary water wavesprofile reconstructionerror boundshodograph transformL2 stabilityPaley-Wiener estimates
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The pith

Perturbations in wave speed, depth, and bed pressure yield sublinear L² errors when recovering solitary wave profiles via Constantin's formula.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The paper establishes that Constantin's explicit reconstruction formula for the free-surface profile of two-dimensional irrotational solitary water waves remains stable when the wave speed, undisturbed depth, and dynamic pressure trace at the bed are all slightly perturbed. It derives an L² error estimate between the true and reconstructed profiles by applying the hodograph transform to convert the free-boundary problem into a fixed-domain holomorphic setting, then using holomorphic extension and Paley-Wiener Fourier decay estimates to control how errors propagate. A sympathetic reader would care because this supplies a concrete stability guarantee for an otherwise exact formula, showing that small inaccuracies in measured or estimated inputs do not destroy the recovery in the L² sense. The analysis includes numerical examples that illustrate the effect of specifically chosen perturbations.

Core claim

For two-dimensional irrotational solitary water waves, simultaneous perturbations in wave speed, undisturbed depth, and the dynamic pressure at the bed produce an L² error in the reconstructed free-surface profile that is controlled by a sublinear function of the total perturbation size. The proof maps the problem via the hodograph transform into a strip where the velocity potential extends holomorphically, invokes Paley-Wiener decay on the Fourier side to quantify the difference, and thereby obtains stability estimates that improve on purely linear bounds.

What carries the argument

Constantin's explicit reconstruction formula for the free-surface elevation from the bed pressure trace, combined with the hodograph transform that straightens the unknown free boundary into a fixed strip and permits holomorphic extension together with Paley-Wiener estimates.

If this is right

  • The reconstruction formula can be applied reliably to mildly inaccurate experimental data without losing L² accuracy.
  • Sublinear error growth means that halving the perturbation size reduces the profile error by a factor better than one-half.
  • Numerical tests with designed perturbations confirm that the theoretical bound captures the observed reconstruction error.
  • The result supplies a quantitative justification for using bottom-pressure measurements to infer surface profiles under realistic noise levels.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

  • Bottom-pressure sensors could be used for surface-profile inference in field measurements with explicit uncertainty estimates derived from this stability result.
  • The holomorphic and Fourier-decay techniques may carry over to other free-boundary inverse problems in ideal fluid dynamics.
  • The sublinear dependence suggests that certain directions of perturbation in the three input quantities are less damaging than a generic linear analysis would predict.

Load-bearing premise

The flow must be a two-dimensional irrotational solitary wave for which the hodograph transform and holomorphic extension are valid, and the perturbations in speed, depth, and pressure must be small enough for the estimates to hold.

What would settle it

Take a known exact solitary wave solution, apply small controlled perturbations to its speed, depth, and bed pressure, reconstruct the profile with the perturbed formula, and check whether the observed L² difference between true and reconstructed profiles obeys the sublinear bound or exceeds it.

Figures

Figures reproduced from arXiv: 2605.15590 by Daniel Sinambela.

Figure 1
Figure 1. Figure 1: The Hodograph transform denote the velocity field in the frame moving at speed c. The steady Euler equations (2.1) in this frame read (w · ∇)w = −∇P − g yˆ, ∇ · w = 0, ∇ × w = 0, yˆ = (0, 1). Using the irrotationality condition and the vector identity (w · ∇)w = ∇ [PITH_FULL_IMAGE:figures/full_fig_p005_1.png] view at source ↗
Figure 2
Figure 2. Figure 2: Reconstruction error due to wave-speed perturbation 5.2. Pressure Perturbation. In this subsection, we consider the case in which only the pressure trace is perturbed, while the wave-speed parameter and the depth remain fixed. More precisely, we set ε = 0, γ = 0, and perturb only the bed pressure through pδ(q) = p(q) + δ(q). The perturbation is different from the one used in [Ble16]. The perturbed pressure… view at source ↗
Figure 3
Figure 3. Figure 3: Reconstruction error due to bed-pressure perturbation 5.3. Depth Perturbation. Now, we consider the case in which only the fluid depth is per￾turbed, while the wave-speed parameter and the pressure trace remain fixed. More precisely, we set ε = 0, δ = 0, and allow only the depth to vary through dγ = d + γ. Therefore, the perturbed recovered profile takes the form η0,0,γ(q) = F −1  sinh(k(d + γ)) k gb0,0(k… view at source ↗
Figure 4
Figure 4. Figure 4: Reconstruction error due to depth perturbation [PITH_FULL_IMAGE:figures/full_fig_p016_4.png] view at source ↗
read the original abstract

We investigate the robustness of Constantin's explicit reconstruction formula for two-dimensional irrotational solitary water waves. This formula recovers the free-surface profile from the dynamic pressure trace at the bed and depends on both the wave speed and the undisturbed depth. We consider simultaneous perturbations in these three quantities and derive an $L^2$ error estimate for the reconstructed profile. The proof uses the hodograph transform, holomorphic extension arguments, and Paley--Wiener Fourier-decay estimates, yielding stability estimates with sublinear dependence on the perturbation size. We include numerical computations to illustrate the effects of specifically designed perturbations.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Referee Report

1 major / 2 minor

Summary. The manuscript derives an L² error estimate for the free-surface profile recovered via Constantin's explicit reconstruction formula for two-dimensional irrotational solitary water waves, under simultaneous small perturbations to the bed dynamic pressure trace, wave speed, and undisturbed depth. The proof applies the hodograph transform to obtain a holomorphic formulation, followed by holomorphic extension and Paley-Wiener Fourier decay estimates, yielding stability bounds with sublinear dependence on the total perturbation size; numerical examples illustrate the effect of specific perturbations.

Significance. If the estimates are rigorously established, the result strengthens the practical utility of the reconstruction formula by quantifying its stability under realistic measurement errors in multiple parameters. The combination of classical complex-analytic tools with numerics is a positive feature, and the sublinear dependence (rather than linear) would be a nontrivial improvement over naive bounds.

major comments (1)
  1. The central L² stability claim rests on applying Paley-Wiener decay to the holomorphic extension of the perturbed pressure trace after the hodograph transform. No explicit lower bound δ(ε) ≥ δ₀ > 0 (independent of the perturbation size ε) on the width of the holomorphic strip for the simultaneously perturbed data is derived or cited; if δ(ε) → 0 as ε → 0, the exponential decay rate deteriorates and the claimed sublinear error bound may fail to hold uniformly. The manuscript should supply this uniform control or show how the hodograph map prevents shrinkage for the joint perturbations in speed, depth, and pressure.
minor comments (2)
  1. The numerical section would benefit from a clearer statement of the exact perturbation forms (e.g., functional expressions or parameter values) to facilitate reproducibility.
  2. Notation for the perturbed quantities (speed, depth, pressure) should be introduced consistently in the statement of the main theorem to avoid ambiguity when comparing to the unperturbed case.

Simulated Author's Rebuttal

1 responses · 0 unresolved

We thank the referee for the careful reading and the constructive comment on the uniform control of the holomorphic strip width. We address this point below and will incorporate the requested clarification in the revised manuscript.

read point-by-point responses
  1. Referee: The central L² stability claim rests on applying Paley-Wiener decay to the holomorphic extension of the perturbed pressure trace after the hodograph transform. No explicit lower bound δ(ε) ≥ δ₀ > 0 (independent of the perturbation size ε) on the width of the holomorphic strip for the simultaneously perturbed data is derived or cited; if δ(ε) → 0 as ε → 0, the exponential decay rate deteriorates and the claimed sublinear error bound may fail to hold uniformly. The manuscript should supply this uniform control or show how the hodograph map prevents shrinkage for the joint perturbations in speed, depth, and pressure.

    Authors: We agree that an explicit uniform lower bound on the width of the holomorphic strip is essential to ensure the Paley-Wiener decay rate remains uniform and the sublinear L² bound holds. In the revised version we will add a new lemma establishing that, for all sufficiently small joint perturbations ε in (speed, depth, pressure), the transformed data after the hodograph map admit holomorphic extension to a strip of width at least δ₀/2, where δ₀ > 0 is the width for the unperturbed solitary wave. The argument relies on the continuous dependence of the hodograph transform on the three parameters in the C¹ topology together with the explicit form of Constantin’s reconstruction formula; small perturbations cannot push the image of the fluid domain arbitrarily close to the boundary of the strip. With this uniform δ₀ the exponential Fourier decay is controlled independently of ε, and the sublinear error estimate follows as stated. We will also include a brief numerical check confirming that the effective strip width remains bounded away from zero in the computed examples. revision: yes

Circularity Check

0 steps flagged

No circularity: derivation applies classical analytic tools to external reconstruction formula

full rationale

The central result is an L² stability estimate derived from the hodograph transform, holomorphic extension, and Paley-Wiener decay applied to simultaneous perturbations of speed, depth, and pressure in Constantin's reconstruction formula. No equation reduces by construction to a fitted parameter or self-referential definition. No load-bearing uniqueness theorem or ansatz is imported via self-citation. The proof chain is independent of the target bound and rests on standard function-theoretic estimates whose validity is external to the present paper.

Axiom & Free-Parameter Ledger

0 free parameters · 1 axioms · 0 invented entities

The central claim rests on the validity of Constantin's reconstruction formula (taken from prior literature) and on standard properties of the hodograph transform and holomorphic functions in the complex plane for irrotational flows. No free parameters, invented entities, or ad-hoc axioms are visible from the abstract.

axioms (1)
  • domain assumption The flow is two-dimensional, irrotational, and the wave is a solitary traveling wave of permanent form.
    This is the setting in which Constantin's formula and the hodograph transform are known to apply.

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