Multi-parameter singular Radon transforms II: the L^p theory

Abstract

The purpose of this paper is to study the $L^p$ boundedness of operators of the form \[ f\mapsto ψ(x) \int f(γ_t(x))K(t)\: dt, \] where ${\gamma }_t(x)$ is a $C^{\infty }$ function defined on a neighborhood of the origin in $(t,x)\in {\mathbb{R}}^N\times {\mathbb{R}}^n$, satisfying ${\gamma }_0(x)\equiv x$, $\psi$ is a $C^{\infty }$ cutoff function supported on a small neighborhood of $0\in {\mathbb{R}}^n$, and $K$ is a "multi-parameter singular kernel" supported on a small neighborhood of $0\in {\mathbb{R}}^N$. We also study associated maximal operators. The goal is, given an appropriate class of kernels $K$, to give conditions on $\gamma$ such that every operator of the above form is bounded on $L^p$ ($1<p<\infty$). The case when $K$ is a Calderón-Zygmund kernel was studied by Christ, Nagel, Stein, and Wainger; we generalize their work to the case when $K$ is (for instance) given by a "product kernel." Even when $K$ is a Calderón-Zygmund kernel, our methods yield some new results. This is the second paper in a three part series. The first paper deals with the case $p=2$, while the third paper deals with the special case when $\gamma$ is real analytic.

41 pages; part 2 in a three part series