English

Square function estimates for conical regions

Classical Analysis and ODEs 2022-03-30 v2

Abstract

We prove square function estimates for certain conical regions. Specifically, let {Δj}\{\Delta_j\} be regions of the unit sphere Sn1\mathbb{S}^{n-1} and let SjfS_j f be the smooth Fourier restriction of ff to the conical region {ξRn:ξ/ξΔj}\{\xi\in\mathbb{R}^n:\xi/|\xi|\in\Delta_j\}. We are interested in the following estimate (jSjf2)1/2pϵδϵfp.\Big\|(\sum_j|S_jf|^2)^{1/2}\Big\|_p\lesssim_\epsilon \delta^{-\epsilon}\|f\|_p. The first result is: when {Δj}\{\Delta_j\} is a set of disjoint δ\delta-balls, then the estimate holds for p=4p=4. The second result is: In R3\mathbb{R}^3, when {Δj}\{\Delta_j\} is a set of disjoint δ×δ1/2\delta\times\delta^{1/2}-rectangles contained in the band S2Nδ({ξ12+ξ22=ξ32})\mathbb{S}^2\cap N_\delta(\{\xi_1^2+\xi_2^2=\xi_3^2\}) and suppf^{ξR3:ξ/ξS2Nδ({ξ12+ξ22=ξ32})}{\rm{supp}}\widehat f\subset \{\xi\in\mathbb{R}^3:\xi/|\xi|\in\mathbb{S}^2\cap N_\delta(\{\xi_1^2+\xi_2^2=\xi_3^2\})\}, then the estimate holds for p=8p=8. The two estimates are sharp.

Keywords

Cite

@article{arxiv.2203.12155,
  title  = {Square function estimates for conical regions},
  author = {Shengwen Gan and Shukun Wu},
  journal= {arXiv preprint arXiv:2203.12155},
  year   = {2022}
}

Comments

27 pages, 5 figures, more references added

R2 v1 2026-06-24T10:22:50.648Z