Oscillating singular integral operators on compact Lie groups revisited

TL;DR

This paper extends Fefferman's weak (1,1) boundedness results for oscillating singular integrals from Euclidean spaces to arbitrary compact Lie groups, highlighting the interplay between kernel conditions, Fourier transforms, and group geometry.

Contribution

It generalizes Fefferman's theorem to compact Lie groups and explores applications to spectral multipliers of the Laplace-Beltrami operator.

Findings

Established weak (1,1) boundedness on compact Lie groups

Linked kernel conditions with Fourier transform properties

Analyzed geometric aspects influencing operator behavior

Abstract

In [24, Theorem 2'] Charles Fefferman has proved the weak (1,1) boundedness for a class of oscillating singular integrals that includes the oscillating spectral multipliers of the Euclidean Laplacian $\Delta,$ namely, operators of the form \begin{equation} T_{\theta}(-\Delta):= (1-\Delta)^{-\frac{n\theta}{4}}e^{i (1-\Delta)^{\frac{\theta}{2}}},\,0\leq \theta <1. \end{equation} The aim of this work is to extend Fefferman's result to oscillating singular integrals on any arbitrary compact Lie group. Applications to oscillating spectral multipliers of the Laplace-Beltrami operator are also considered. The proof of our main theorem illustrates the delicate relationship between the condition on the kernel of the operator, its Fourier transform (defined in terms of the representation theory of the group) and the microlocal/geometric properties of the group.