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arXiv · 2610.40820

Sharp convex body sparse bounds and quantitative matrix weighted estimates for Hilbert transforms along curves

Xi Cen
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Abstract

We prove convex body sparse bounds for coordinatewise Hilbert transforms along monomial curves and local $C^d$ curves with uniformly nonvanishing torsion on the closed integration interval. Adapting the scalar estimates of Cladek--Ou \cite{CladekOu2018} and the lifting method of Laukkarinen--Lorist \cite{LaukkarinenLorist2026} to the anisotropic geometry, we obtain one sparse family of genuine curve-adapted boxes and quantitative $L^p(W)$ bounds for matrix weights. The convex body sparse exponent range is sharp up to its boundary: estimates hold in the interior of $Ω_d$, while any fixed finite number of sparse families fails outside $\overline{Ω_d}$ when $1/r+1/s>1$. We also establish an explicit endpoint-contact obstruction. For every interior planar exponent pair, a polynomial curve with positive torsion on the open integration interval violates the full-interval sparse estimate.

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Xi Cen. 2026-10-29. Sharp convex body sparse bounds and quantitative matrix weighted estimates for Hilbert transforms along curves. https://arxiv.org/abs/2610.40820

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