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arXiv 1802.00350math.CAmath.APmath.COmath.MG
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一个$L^2$ -恒等式和固定距离问题

An $L^2$-identity and pinned distance problem

Bochen Liu

摘要:

设$μ$是$E\subset\mathbb{R}^d$上的Frostman测度.球平均衰变$$\int_{S^{d-1}}|\widehatμ(rω)|^2\,dω\lesssim r^{-β} $$最初是用来攻击法尔科纳距离猜想,通过马蒂拉的积分。在本文中,我们认为钉扎距离问题,一个更强的版本的Falconer距离问题,并表明,球面平均衰减意味着相同的维度阈值上两者。特别地,利用最著名的球平均估计,我们显著地改进了Peres-Schlag关于钉扎距离问题的结果。其思想是将固定距离问题简化为球面平均值适用的积分。关键要素是以下身份。使用组作用参数,我们表明,对于任何施瓦茨功能$f$上的$\mathbb{R}^d$和任何$x\in\mathbb{R}^d$,$$\int_0^\infty |ω_t*f(x)|^2\,t^{d-1}dt\,=\int_0^\infty|\widehat{ω_r}*f(x)|^2\,r^{d-1}dr,$$其中$ω_r$是归一化表面测量$r S^{d-1}$。一个有趣的评论是,右手边可以很容易地看到等于$$c_d\int\left|D_x^{-\frac{d-1}{2}}e^{-2πi t\sqrt{-Δ}}f(x)\right|^2\,dt=c_d'\int\left|D_x^{-\frac{d-2}{2}}e^{2πi tΔ}f(x)\right|^2\,dt.$$一个替代推导马蒂拉的积分通过群作用也给出了附录。

英文摘要:

Let $μ$ be a Frostman measure on $E\subset\mathbb{R}^d$. The spherical average decay $$\int_{S^{d-1}}|\widehatμ(rω)|^2\,dω\lesssim r^{-β} $$ was originally used to attack Falconer distance conjecture, via Mattila's integral. In this paper we consider the pinned distance problem, a stronger version of Falconer distance problem, and show that spherical average decay implies the same dimensional threshold on both of them. In particular, with the best known spherical average estimates, we improve Peres-Schlag's result on pinned distance problem significantly. The idea is to reduce the pinned distance problem to an integral where spherical averages apply. The key ingredient is the following identity. Using a group action argument, we show that for any Schwartz function $f$ on $\mathbb{R}^d$ and any $x\in\mathbb{R}^d$, $$\int_0^\infty |ω_t*f(x)|^2\,t^{d-1}dt\,=\int_0^\infty|\widehat{ω_r}*f(x)|^2\,r^{d-1}dr,$$ where $ω_r$ is the normalized surface measure on $r S^{d-1}$. An interesting remark is that the right hand side can be easily seen equal to $$c_d\int\left|D_x^{-\frac{d-1}{2}}e^{-2πi t\sqrt{-Δ}}f(x)\right|^2\,dt=c_d'\int\left|D_x^{-\frac{d-2}{2}}e^{2πi tΔ}f(x)\right|^2\,dt.$$ An alternative derivation of Mattila's integral via group actions is also given in the Appendix.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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