High-dimensional pp decoupling conjecture for smooth hypersurfaces

Let ϕ:Rn1R\phi:\mathbb{R}^{n-1}\to\mathbb{R} be smooth, and let Mϕ={(ξ,ϕ(ξ)):ξ[0,1]n1}\mathcal{M}_{\phi}=\{(\xi,\phi(\xi)):\xi\in[0,1]^{n-1}\}. A set S[0,1]n1S\subset[0,1]^{n-1} is (ϕ,δ)(\phi,\delta)-flat when it satisfies the flatness condition defined in the paper. For a measurable function f:RnCf:\mathbb{R}^n\to\mathbb{C} and measurable SS, let fSf_S denote the Fourier restriction of ff to S×RS\times\mathbb{R}. High-dimensional pp decoupling conjecture. For every ϵ>0\epsilon>0, there is a sufficiently large A=A(ϵ)A=A(\epsilon) such that, for every δ>0\delta>0, one can find a finitely overlapping collection Sδ\mathcal{S}_{\delta} of subsets of [0,1]n1[0,1]^{n-1} satisfying

SSδχSCϵlog(δ1),\sum_{S\in\mathcal{S}_{\delta}}\chi_S\leq C_{\epsilon}\log(\delta^{-1}),

with every SS (ϕ,Aδ)(\phi,A\delta)-flat, and such that for 2p2(n+1)n12\leq p\leq\frac{2(n+1)}{n-1},

fLpCϵδϵ(#Sδ)121p(SSδfSLpp)1p\|f\|_{L^p}\leq C_{\epsilon}\delta^{-\epsilon}(\#\mathcal{S}_{\delta})^{\frac12-\frac1p}\left(\sum_{S\in\mathcal{S}_{\delta}}\|f_S\|_{L^p}^p\right)^{\frac1p}

for all ff whose Fourier supports are contained in Nδ(Mϕ)N_{\delta}(\mathcal{M}_{\phi}). This is proposed as a possible extension of p\ell^p decoupling to higher dimensions; the statement is conjectural for general smooth ϕ\phi.

Sources & referencesView supporting material

Primary source

Larry Guth, Dominique Maldague and Changkeun Oh, “l^2 decoupling theorem for surfaces in R^3”, arXiv:2403.18431 (2025).

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