The Lipschitz Kakeya maximal-function conjecture

Let vv be a Lipschitz map from R2\mathbb R^2 to the unit circle. For a rectangle RR of sufficiently short length, let VR=Rv1(EXR)\operatorname V R=R\cap v^{-1}(\operatorname{EX}R), where EXR\operatorname{EX}R denotes the interval of directions determined by RR, and define

Mδ,vf(x)=supVRδR1R(x)RRf(y)dy.\operatorname M_{\delta,v}f(x)=\sup_{|\operatorname V R|\geq\delta|R|}\frac{\mathbf 1_R(x)}{|R|}\int_R|f(y)|\,dy.

Lipschitz Kakeya maximal-function conjecture. For some 1<p<21<p<2 and some finite NN, for all 0<δ<10<\delta<1 and all Lipschitz vector fields vv, the operator Mδ,v\operatorname M_{\delta,v} maps Lp(R2)L^p(\mathbb R^2) to Lp,(R2)L^{p,\infty}(\mathbb R^2) with norm at most δN\lesssim\delta^{-N}. The known L2L^2 bound has norm δ1/2\lesssim\delta^{-1/2}, but the asserted subquadratic estimate is not verified in the source.

Sources & referencesView supporting material

Primary source

Michael Lacey and Xiaochun Li, “On a Conjecture of EM Stein on the Hilbert Transform on Vector Fields”, arXiv:0704.0808 (2008).

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