Stein's conjecture for weighted extension operators

Let ΣRd\Sigma\subset\mathbb{R}^d be a C2C^2 hypersurface with surface measure dσ\mathrm{d}\sigma, let fL2(Σ;dσ)f\in L^2(\Sigma;\mathrm{d}\sigma), and let ww be a nonnegative weight. Let N(σ)N(\sigma) denote the normal to Σ\Sigma at σ\sigma, and let XwXw be the X-Ray transform of ww. Stein's conjecture. Under the hypotheses of the Mizohata–Takeuchi conjecture, one has

RdEf2wdxΣf(σ)2supN(σ)Xw()dσ(σ).\int_{\mathbb{R}^d}|\mathcal E f|^2w\,\mathrm{d}x\lesssim\int_\Sigma |f(\sigma)|^2\sup_{\ell\parallel N(\sigma)}Xw(\ell)\,\mathrm{d}\sigma(\sigma).

The supplied text presents this as a conjecture arising from the connection between Kakeya or Nikodym maximal functions and Bochner–Riesz multipliers; it gives no resolution status.

Sources & referencesView supporting material

Primary source

Hannah Cairo, “A Counterexample to the Mizohata-Takeuchi Conjecture”, arXiv:2502.06137 (2025).

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