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arXiv 2402.08615math.CAmath.AP
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具有$L^2$-有界Riesz变换的测度与Painlevé问题

The measures with $L^2$-bounded Riesz transform and the Painlevé problem

Damian Dąbrowski, Xavier Tolsa

AI总结:

本文刻画了$\mathbb R^{n+1}$中具有$n$次多项式增长的测度使得$n$维Riesz变换属于$L^2(\mu)$的几何条件,并由此得到Lipschitz调和函数可去集的度量几何刻画及其在双Lipschitz映射下的不变性。

摘要:

本文给出了$\nmathbb R^{n+1}$中具有$n$次多项式上增长的测度$\mu$的几何刻画,使得$n$维Riesz变换$R\mu(x) = \int \frac{x-y}{|x-y|^{n+1}}\\,d\mu(y)$属于$L^2(\mu)$。更精确地,证明了$$\\|R\mu\\|_{L^2(\mu)}^2 + \\|\mu\\|\approx \int\\!\\!\int_0^\infty \beta_{2,\mu}(x,r)^2\\,\frac{\mu(B(x,r))}{r^n}\\,\frac{dr}r\\,d\mu(x) + \\|\mu\\|,$$其中$\beta_{\mu,2}(x,r)^2 = \inf_L \frac1{r^n}\int_{B(x,r)} \left(\frac{\mathrm{dist}(y,L)}r\right)^2\\,d\mu(y),$下确界取遍所有仿射$n$-平面$L\subset\mathbb R^{n+1}$。作为推论,我们获得了Lipschitz调和函数的可去集在度量几何势意义下的刻画,并由此推出Lipschitz调和函数的可去集类在双Lipschitz映射下保持不变。

英文摘要:

In this work we provide a geometric characterization of the measures $μ$ in $\mathbb R^{n+1}$ with polynomial upper growth of degree $n$ such that the $n$-dimensional Riesz transform $Rμ(x) = \int \frac{x-y}{|x-y|^{n+1}}\,dμ(y)$ belongs to $L^2(μ)$. More precisely, it is shown that $$\|Rμ\|_{L^2(μ)}^2 + \|μ\|\approx \int\!\!\int_0^\infty β_{2,μ}(x,r)^2\,\frac{μ(B(x,r))}{r^n}\,\frac{dr}r\,dμ(x) + \|μ\|,$$ where $β_{μ,2}(x,r)^2 = \inf_L \frac1{r^n}\int_{B(x,r)} \left(\frac{\mathrm{dist}(y,L)}r\right)^2\,dμ(y),$ with the infimum taken over all affine $n$-planes $L\subset\mathbb R^{n+1}$. As a corollary, we obtain a characterization of the removable sets for Lipschitz harmonic functions in terms of a metric-geometric potential and we deduce that the class of removable sets for Lipschitz harmonic functions is invariant by bilipschitz mappings.

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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