Anna Wedestig

Weighted inequalities for the Sawyer two-dimensional Hardy operator and its limiting geometric mean operator

We consider and a corresponding geometric mean operator. E. T. Sawyer showed that the Hardy-type inequality could be characterized by three independent conditions on the weights. We give a simple proof of the fact that if the weight is of product type, then in fact only one condition is needed. Moreover, by using this information and by performing a limiting procedure we can derive a weight characterization of the corresponding two-dimensional Pólya-Knopp inequality with the geometric mean operator involved.

A NEW APPROACH TO THE SAWYER AND SINNAMON CHARACTERIZATIONS OF HARDY'S INEQUALITY FOR DECREASING FUNCTIONS

Abstract Some Hardy type inequalities for decreasing functions are characterized by one condition (Sinnamon), while others are described by two independent conditions (Sawyer). In this paper we make a new approach to deriving such results and prove a theorem, which covers both the Sinnamon result and the Sawyer result for the case where one weight is increasing. In all cases we point out that the characterizing condition is not unique and can even be chosen among some (infinite) scales of conditions.