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The Dual Elements of Function Sets and Fefferman–Stein Decomposition of Triebel–Lizorkin Functions via Wavelets
Computational Methods and Function Theory ( IF 0.6 ) Pub Date : 2020-02-27 , DOI: 10.1007/s40315-020-00309-w
Qixiang Yang , Tao Qian

Let \(D\in \mathbb {N}\), \(q\in [2,\infty )\) and \((\mathbb {R}^D,|\cdot |,dx)\) be the Euclidean space equipped with the D-dimensional Lebesgue measure. In this article, we establish the Fefferman–Stein decomposition of Triebel–Lizorkin spaces \(\dot{F}^0_{\infty ,\,q'}(\mathbb {R}^D)\) with the help of the dual on function sets which have special topological structure. A function in Triebel–Lizorkin spaces \(\dot{F}^0_{\infty ,\,q'}(\mathbb {R}^D)\) can be written as a specific combination of \(D+1\) functions in \(\dot{F}^0_{\infty ,\,q'}(\mathbb {R}^D) \cap L^{\infty }(\mathbb {R}^D)\). To get such a decomposition, first, some auxiliary function spaces \(\mathrm {WE}^{1,\,q}({\mathbb {R}}^D)\) and \(\mathrm {WE}^{\infty ,\,q'}(\mathbb {R}^D)\) are defined via wavelet expansions. It is shown that$$\begin{aligned} {\dot{F}^0_{1,\,q}({\mathbb {R}}^D)}\subsetneqq L^{1}({\mathbb {R}}^D) \cup {\dot{F}^0_{1,\,q}({\mathbb {R}}^D)}\subset \mathrm{WE}^{1,\,q}({\mathbb {R}}^D)\subset L^{1}({\mathbb {R}}^D) + {\dot{F}^0_{1,\,q}({\mathbb {R}}^D)}\end{aligned}$$and \(\mathrm {WE}^{\infty ,\,q'}(\mathbb {R}^D)\) is strictly contained in \(\dot{F}^0_{\infty ,\,q'}(\mathbb {R}^D)\). Next, the Riesz transform characterization of Triebel–Lizorkin spaces \(\dot{F}^0_{1,\,q}(\mathbb {R}^D)\) by the function set \(\mathrm {WE}^{1,\,q}({\mathbb {R}}^D)\) is established. Then the dual of \(\mathrm {WE}^{1,\,q}({\mathbb {R}}^D)\) is considered. As a consequence of the above results, a Riesz transform characterization of Triebel–Lizorkin spaces \(\dot{F}^0_{1,\,q}(\mathbb {R}^D)\) by Banach space \(L^{1}({\mathbb {R}}^D) + {\dot{F}^0_{1,\,q}({\mathbb {R}}^D)}\) is obtained. Although Fefferman–Stein type decompositions when \(D=1\) was obtained by Lin et al. (Mich Math J 62:691–703, 2013), as was pointed out by Lin et al., the approach used in the case \(D=1\) cannot be applied to the cases \(D\ge 2\). In the latter cases, some new skills related to Riesz transforms are to be developed.

中文翻译:

函数集的对偶元素和Triebel-Lizorkin函数通过小波的费弗曼-斯坦分解

\(D \ in \ mathbb {N} \)\(q \ in [2,\ infty} \)\((\ mathbb {R} ^ D,| \ cdot |,dx)\)为配备D维Lebesgue测度的欧几里德空间。在这篇文章中,我们建立TRIEBEL-Lizorkin空间的Fefferman斯坦分解\(\点{F} ^ 0 _ {\ infty,\ Q'}(\ mathbb {R} ^ d)\)用的帮助具有特殊拓扑结构的双重功能集。Triebel–Lizorkin空间\(\ dot {F} ^ 0 _ {\ infty,\,q'}(\ mathbb {R} ^ D)\)中的函数可以写为\(D + 1 \ )\(\ dot {F} ^ 0 _ {\ infty,\,q'}(\ mathbb {R} ^ D)\ cap L ^ {\ infty}(\ mathbb {R} ^ D)\)中起作用。为了得到这样的分解,首先,一些辅助函数空间\(\ mathrm {WE} ^ {1,\,q}({\ mathbb {R}} ^ D)\)\(\ mathrm {WE} ^ { \ infty,\,q'}(\ mathbb {R} ^ D)\)是通过小波展开定义的。结果表明$$ \ begin {aligned} {\ dot {F} ^ 0_ {1,\,q}({\ mathbb {R}} ^ D)} \ subsetneqq L ^ {1}({\ mathbb { R}} ^ D)\ cup {\ dot {F} ^ 0_ {1,\,q}({\ mathbb {R}} ^ D)} \ subset \ mathrm {WE} ^ {1,\,q} ({\ mathbb {R}} ^ D)\子集L ^ {1}({\ mathbb {R}} ^ D)+ {\ dot {F} ^ 0_ {1,\,q}({\ mathbb { R}} ^ D)} \ end {aligned} $$\(\ mathrm {WE} ^ {\ infty,\,q'}(\ mathbb {R} ^ D)\)严格包含在\(\点{F} ^ 0 _ {\ infty,\,q'}(\ mathbb {R} ^ D)\)。接下来,对Triebel–Lizorkin空间\(\ dot {F} ^ 0_ {1,\,q}(\ mathbb {R} ^ D)\)进行Riesz变换表征通过功能集\(\ mathrm {WE} ^ {1,\,q}({\ mathbb {R}} ^ D)\)建立。然后考虑\(\ mathrm {WE} ^ {1,\,q}({\ mathbb {R}} ^ D)\)的对偶。以上结果的结果是,Triebel–Lizorkin空间\(\ dot {F} ^ 0_ {1,\,q}(\ mathbb {R} ^ D)\)的Riesz变换特征由Banach空间\(L获得^ {1}({\ mathbb {R}} ^ D)+ {\ dot {F} ^ 0_ {1,\,q}({\ mathbb {R}} ^ D)} \\)。尽管当Lin等人获得\(D = 1 \)时Fefferman–Stein型分解。(Mich Math J 62:691–703,2013),正如Lin等人指出的那样,案例\(D = 1 \)中使用的方法无法应用于案例\(D \ ge 2 \)。在后一种情况下,将开发一些与Riesz变换有关的新技能。
更新日期:2020-02-27
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