摘要
Let a:=(a1,…,an)∈[1,∞)n,p:=(p1,…,pn)∈(0,1]n,Hpa(R^(n))be the anisotropic mixed-norm Hardy space associated with adefined via the radial maximal function,and let f belong to the Hardy space Hpa(R^(n)).In this article,we show that the Fourier transform fcoincides with a continuous function g onℝn in the sense of tempered distributions and,moreover,this continuous function g,multiplied by a step function associated with a,can be pointwisely controlled by a constant multiple of the Hardy space norm of f.These proofs are achieved via the known atomic characterization of Hpa(R^(n))and the establishment of two uniform estimates on anisotropic mixed-norm atoms.As applications,we also conclude a higher order convergence of the continuous function gat the origin.Finally,a variant of the Hardy-Littlewood inequality in the anisotropic mixed-norm Hardy space setting is also obtained.All these results are a natural generalization of the well-known corresponding conclusions of the classical Hardy spaces Hp(R^(n))with p∈0,1],and are even new for isotropic mixed-norm Hardy spaces on∈n.
基金
This work was partially supported by the National Natural Science Foundation of China(Grant Nos.11971058,12071197)
the National Key Research and Development Program of China(Grant No.2020YFA0712900)
Der-Chen Chang was partially supported by an NSF grant DMS-1408839 and a McDevitt Endowment Fund at Georgetown University.
