paper

On Kato-Ponce and fractional Leibniz

arXiv:1609.01780 · doi:10.4171/rmi/1049

Abstract

We show that in the Kato-Ponce inequality , the term on the RHS can be replaced by . This solves a question raised in Kato-Ponce \cite{KP88}. We propose and prove a new fractional Leibniz rule for and similar operators, generalizing the Kenig-Ponce-Vega estimate \cite{KPV93} to all . We also prove a family of generalized and refined Kato-Ponce type inequalities which include many commutator estimates as special cases. To showcase the sharpness of the estimates at various endpoint cases, we construct several counterexamples. In particular, we show that in the original Kato-Ponce inequality, the -norm on the RHS cannot be replaced by the weaker BMO norm. Some divergence-free counterexamples are also included.

To appear in revista matemática iberoamericana

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