Sharp small-ensemble decoupling for the paraboloid

Let RR be a large parameter, let BRB_R be a ball or cube of radius or side length RR in R3{\mathbb R}^3, and let ESFE_SF be the extension operator for the two-dimensional paraboloid restricted to S[0,1]2S\subset[0,1]^2. Assume each SiS_i is a R\sqrt{R}-set, meaning a large ensemble containing R\sqrt{R} canonical 1/R1/\sqrt{R}-squares, with the sets SiS_i forming the family under consideration. Sharp small-ensemble decoupling for the paraboloid. For 2p10/32\le p\le10/3, one has

EFLp(BR)ϵR12(121p)+ϵ(i=1R1/2ESiFLp(BR)p)1/p.\|EF\|_{L^p(B_R)}\lesssim_{\epsilon}R^{\frac12(\frac12-\frac1p)+\epsilon}\left(\sum_{i=1}^{R^{1/2}}\|E_{S_i}F\|_{L^p(B_R)}^p\right)^{1/p}.

The estimate would be particularly significant at p=10/3p=10/3, where the corresponding case is linked to the sharp restriction estimate. The source gives no resolution status for this conjecture.

Sources & referencesView supporting material

Primary source

Ciprian Demeter, “Beyond canonical decoupling”, arXiv:2402.04989 (2024).

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