On an operator arising in the Calderón-Zygmund method of rotations and the Bramble-Hilbert lemma.
In this article sharp estimates are obtained for an operator that is a quadratic average with respect to v of one-dimensional Hardy-Littlewood maximal functions in the directions v. This operator arises naturally in Fourier analysis and numerical analysis.
Fefferman
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University of Chicago, 5734 South University Avenue, Chicago, Illinois 60637.