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The two weight T1 theorem for fractional Riesz...
Journal article

The two weight T1 theorem for fractional Riesz transforms when one measure is supported on a curve

Abstract

Let σ and ω be locally finite positive Borel measures on ℝn. We assume that at least one of the two measures σ and ω is supported on a regular C1,δ curve in ℝn. Let Rα,n be the α-fractional Riesz transform vector on ℝn. We prove the T1 theorem for Rα,n: namely that Rα,n is bounded from L2(σ) to L2(σ) if and only if the A2α$${\cal A}_2^\alpha $$ conditions with holes hold, the punctured A2α$$A_2^\alpha $$ conditions hold, and the cube testing condition for Rα,n and its dual both hold. The special case of the Cauchy transform, n = 2 and α = 1, when the curve is a line or circle, was established by Lacey, Sawyer, Shen, Uriarte-Tuero and Wick in [LaSaShUrWi]. This T1 theorem represents essentially the most general T1 theorem obtainable by methods of energy reversal. More precisely, for the pushforwards of the measures σ and ω, under a change of variable to straighten out the curve to a line, we use reversal of energy to prove that the quasienergy conditions in [SaShUr7] are implied by the A2α$${\cal A}_2^\alpha $$ with holes, punctured A2α$$A_2^\alpha $$, and quasicube testing conditions for Rα,n. Then we apply the main theorem in [SaShUr7] to deduce the T1 theorem above.

Authors

Sawyer ET; Shen C-Y; Uriarte-Tuero I

Journal

Journal d'Analyse Mathématique, Vol. 142, No. 2, pp. 453–520

Publisher

Springer Nature

Publication Date

November 1, 2020

DOI

10.1007/s11854-020-0141-4

ISSN

0021-7670

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