Multiplier conditions for Boundedness into Hardy spaces

Abstract

In the present work, we find useful and explicit necessary and sufficient conditions for linear and multilinear multiplier operators of Coifman-Meyer type, finite sum of products of Calder\'on-Zygmund operators, and also of intermediate types to be bounded from a product of Lebesgue or Hardy spaces into a Hardy space. These conditions state that the symbols of the multipliers $\sigma(\xi_1,\dots , \xi_m)$ and their derivatives vanish on the hyperplane $\xi_1+\cdots+\xi_m=0$.