The Cauchy Singular Integral Operator on Weighted Variable Lebesgue Spaces

TL;DR

This paper characterizes the boundedness of the Cauchy singular integral operator on weighted variable Lebesgue spaces with log-H"older continuous exponents, establishing a necessary and sufficient condition on the weight.

Contribution

It provides a precise criterion for the boundedness of the Cauchy singular integral operator on weighted variable Lebesgue spaces with log-H"older continuous exponents.

Findings

Boundedness characterized by a Muckenhoupt-type condition on weights.

Necessary and sufficient condition involving localized norms of weights.

Extension of classical results to variable exponent and weighted setting.

Abstract

Let $p:\R\to(1,\infty)$ be a globally log-H\"older continuous variable exponent and $w:\R\to[0,\infty]$ be a weight. We prove that the Cauchy singular integral operator $S$ is bounded on the weighted variable Lebesgue space $L^{p(\cdot)}(\R,w)=\{f:fw\in L^{p(\cdot)}(\R)\}$ if and only if the weight $w$ satisfies \[ \sup_{-\infty<a<b<\infty} \frac{1}{b-a}\|w\chi_{(a,b)}\|_{p(\cdot)}\|w^{-1}\chi_{(a,b)}\|_{p'(\cdot)}<\infty \quad (1/p(x)+1/p'(x)=1). \]