In this paper, we prove that the \(L^p(\mathbb {R}^d)\) norm of the maximal truncated Riesz transform in terms of the \(L^p(\mathbb {R}^d)\) norm of Riesz transform is dimension-free for any \(2\le p<\infty \), using integration by parts formula for radial Fourier multipliers. Moreover, we show that
$$\begin{aligned} \Vert R_j^*f\Vert _{L^p}\le \left( {2+\frac{1}{\sqrt{2}}}\right) ^{\frac{2}{p}}\Vert R_jf\Vert _{L^p},\ \ \text{ for }\ \ p\ge 2,\ \ d\ge 2. \end{aligned}$$
As byproducts of our calculations, we infer the \(L^p\) norm contractivity of the truncated Riesz transforms \(R^t_j\) in terms of \(R_j\), and their accurate \(L^p\) norms. More precisely, we prove:
$$\begin{aligned} \Vert R^t_jf\Vert _{L^p}\le \Vert R_jf\Vert _{L^p} \end{aligned}$$
and
$$\begin{aligned} \Vert R^t_j\Vert _{L^p}=\Vert R_j\Vert _{L^p}, \end{aligned}$$
for all \(1<p<+\infty ,\) \(j\in \{1,\dots ,d\}\), and \(t>0.\)
Publication:
Mathematische Annalen (03 October 2023)
http://dx.doi.org/10.1007/s00208-023-02736-1
Author:
Jinsong Liu
HLM, Academy of Mathematics and Systems Science, Chinese Academy of Sciences, Beijing, 100190, China
School of Mathematical Sciences, University of Chinese Academy of Sciences, Beijing, 100049, China
Email: liujsong@math.ac.cn
Petar Melentijevi?
Matemati?ki fakultet, University of Belgrade, Beograd, Serbia
Jian-Feng Zhu
School of Mathematical Sciences, Huaqiao University, Quanzhou, 362021, China
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