Curvature-controlled Fourier decay conjecture for convex planar sets

Let KR2K\subset\mathbb{R}^2 be a convex compact set with piece-wise smooth boundary, and let κ(P)\kappa(P) denote the curvature at PKP\in\partial K. Set

ν=minPKκ(P).\nu=\min_{P\in\partial K}\kappa(P).

Curvature-controlled Fourier decay conjecture. There exists an absolute constant C1>0C_1>0 such that

supωR2ω3/2χ^K(ω)C1ν.\sup_{\omega\in\mathbb{R}^2}|\omega|^{3/2}|\widehat{\chi}_K(\omega)|\le\frac{C_1}{\sqrt{\nu}}.

Moreover, this estimate is sharp: there exists an absolute constant C2>0C_2>0 and a sequence {ωn}R2\{\omega_n\}\subset\mathbb{R}^2 with ωn|\omega_n|\rightarrow\infty such that

ωn3/2χ^K(ωn)C2ν+o(1).|\omega_n|^{3/2}|\widehat{\chi}_{K}(\omega_n)|\ge\frac{C_2}{\sqrt{\nu}}+o(1).

The conjecture proposes a curvature-dependent uniform Fourier decay estimate for the indicator of a convex planar set, together with sharpness of the dependence on the minimum curvature. The supplied text does not establish the claim or provide evidence of its resolution, so its status remains open.

Sources & referencesView supporting material

Primary source

Martin Lind, “Fourier transform inequalities, lattice point discrepancy, asymptotic behavior, oscillatory integrals”, arXiv:2208.07837 (2026).

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