A Sufficient Condition for Haar Multipliers in Triebel-Lizorkin Spaces
摘要
We consider Haar multiplier operators \(T_m\) acting on Sobolev spaces, and more generally Triebel-Lizorkin spaces \(F^s_{p,q}({\mathbb R})\) , for indices in which the Haar system is not unconditional. When m depends only on the Haar frequency, we give a sufficient condition for the boundedness of \(T_m\) in \(F^s_{p,q}\) , in terms of the variation norms \(\|m\|_{V_u}\) , which is optimal in u (up to endpoints) when \(p, q> 1\) .