© 1987 by London Mathematical Society
A Note on a Littlewood-Paley Inequality for Arbitrary Intervals in R2
Department of Mathematics, University of Chicago Illinois, USA
Received 28 February 1986.
Let P = {Ri}i
1 be an arbitrary collection of mutually disjoint intervals in Rn. For every i
1, let Si denote the multiplier operator of symbol Ri; that is, (Sif)^=
R
. Consider now the Littlewood-Paley square function
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It has recently been proved by J. L. Rubio de Francia (when n = 1) and by J.-L. Journé (for general n) that the sublinear operatorf
f is bounded on Lp for 2
p <
. The purpose of this note is to present a simple proof of the boundedness of
for n = 2 or, with more generality, for arbitrary intervals in Rn whose sides have no more than two different sizes. The main ingredient of the proof is the use of a covering lemma due to Journé which has been found to have many interesting applications in the setting of product domains.
Current address: Universidad Autónoma de Madrid, Division de Matematicas, 28049 Madrid, Spain
