It is well known that standard Calderón-Zygmund singular integral operators with isotropic and nonisotropic homogeneities are bounded on the classical Hp(ℝm) and nonisotropic Hh p(ℝm), respectively. In this paper, we develop a new Hardy space theory and prove that the composition of two Calderón-Zygmund singular integral operators with different homogeneities is bounded on this new Hardy space. Such a Hardy space has a multiparameter structure associated with the underlying mixed homogeneities arising from the two singular integral operators under consideration. The Calderón-Zygmund decomposition and an interpolation theorem hold on these new Hardy spaces.
- Almost orthogonality estimates
- Calderón-Zygmund operators
- Discrete Calderón's identity
- Discrete Littlewood-Paley-Stein square functions
- Hardy spaces