On the Poincar\'e inequality on open sets in $\mathbb{R}^n$

A. -K. Gallagher

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arXiv · 2307.13641

On the Poincar\'e inequality on open sets in $\mathbb{R}^n$

A. -K. Gallagher

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Abstract

We show that the Poincar\'{e} inequality holds on an open set $D\subset\mathbb{R}^n$ if and only if $D$ admits a smooth, bounded function whose Laplacian has a positive lower bound on $D$. Moreover, we prove that the existence of such a bounded, strictly subharmonic function on $D$ is equivalent to the finiteness of the strict inradius of $D$ measured with respect to the Newtonian capacity. We also obtain a sharp upper bound, in terms of this notion of inradius, for the smallest eigenvalue of the Dirichlet--Laplacian.

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A. -K. Gallagher. 2023-07-25. On the Poincar\'e inequality on open sets in $\mathbb{R}^n$. https://arxiv.org/abs/2307.13641

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