The off-diagonal Nikodym maximal-function conjecture

For 1d<n1\leq d<n, let Nδ\mathcal N_\delta denote the (d,n)(d,n)-Nikodym maximal function. For 1pnd+11\leq p\leq n-d+1, set q=p(nd)q=p'(n-d), where pp' is the Hölder conjugate of pp. Off-diagonal Nikodym conjecture. For all ε>0\varepsilon>0,

Nδf:Lp(Rn)Lq(Rn)εδ(nd+1pp)(logδ1)1p(nd).\|\mathcal N_\delta f:L^p(\mathbb{R}^n)\to L^q(\mathbb{R}^n)\|\lesssim_\varepsilon \delta^{-\left(\frac{n-d+1-p}{p}\right)}(\log\delta^{-1})^{\frac{1}{p'(n-d)}}.

This is proposed by interpolating the preceding conjectural estimate with the trivial L1LL^1\to L^\infty bound. The supplied text gives no resolution of this off-diagonal conjecture.

Sources & referencesView supporting material

Primary source

Francesco Di Plinio and Ioannis Parissis, “Maximal subspace averages”, arXiv:2107.02109 (2021).

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