A simple proof of Fefferman-Stein type characterization of ${\rm CMO}(\mathbb {R}^{n})$ space.
(English).Czechoslovak Mathematical Journal,
vol. 75
(2025),
issue 2,
pp. 599-610
Summary: We give a simple proof of Fefferman-Stein type characterization of the space ${\rm CMO}(\mathbb {R}^{n})$, that is, $f\in {\rm CMO} (\mathbb {R}^{n})$ if and only if $$ f=\phi +\sum _{j=1}^{n}R_{j}\varphi _{j}, $$ where $\phi ,\varphi _{j}\in {C_{0}(\mathbb {R}^{n})}$ and $R_{j}$, $j=1,2,\ldots ,n$, are the Riesz transforms. Notice that this result was established by G. Bourdaud (2002), but his proof depends on the Fefferman-Stein type decomposition of the space ${\rm VMO}(\mathbb {R}^{n})$ obtained by D. Sarason (1975). We will provide a direct method to prove this conclusion.
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