Abstract

Using the notion of inferior mean due to M. Heins, we establish two inequalities for such a mean relative to a positive harmonic function defined on the open unit ball or half-space in .

Highlights

  • Wu showed in [4] that for a positive harmonic function in the unit disc, one has in most cases inequality, while equality occurs for functions whose boundary measures are absolutely continuous

  • The bound is achieved for functions whose boundary measures, for example, are purely singular

  • For any positive harmonic function u on Ω with boundary measure μ, there exists the following inequality: IM(u) ≤ μ. Equality occurs for those u whose boundary measures μ are absolutely continuous, when the inferior mean is attained along boundaries of Aδ not equal to S as δ → 0

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Summary

Introduction

Wu showed in [4] that for a positive harmonic function in the unit disc, one has in most cases inequality, while equality occurs for functions whose boundary measures are absolutely continuous. She showed that there exists a nonzero lower bound of the lim inf for this class of functions in the disc. For any positive harmonic function u on Ω with boundary measure μ, there exists the following inequality: IM(u) ≤ μ Equality occurs for those u whose boundary measures μ are absolutely continuous, when the inferior mean is attained along boundaries of Aδ not equal to S as δ → 0. The proofs rely on Sard’s theorem (see [3]), and inequality (2.5) obtained below

A surface measure lemma
Poisson kernel
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