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Main Authors: Kim, Hanna N., Laugesen, Richard S.
Format: Preprint
Published: 2025
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Online Access:https://arxiv.org/abs/2501.15029
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author Kim, Hanna N.
Laugesen, Richard S.
author_facet Kim, Hanna N.
Laugesen, Richard S.
contents The third eigenvalue of the Robin Laplacian on a simply-connected planar domain of given area is bounded above by the corresponding eigenvalue of a disjoint union of two equal disks, for Robin parameters in $[-4π,4π]$. This sharp inequality was known previously only for negative parameters in $[-4π,0]$, by Girouard and Laugesen. Their proof fails for positive Robin parameters because the second eigenfunction on a disk has non-monotonic radial part. This difficulty is overcome for parameters in $(0,4π]$ by means of a degree-theoretic approach suggested by Karpukhin and Stern that yields suitably orthogonal trial functions.
format Preprint
id arxiv_https___arxiv_org_abs_2501_15029
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Two disks maximize the third Robin eigenvalue: positive parameters
Kim, Hanna N.
Laugesen, Richard S.
Spectral Theory
The third eigenvalue of the Robin Laplacian on a simply-connected planar domain of given area is bounded above by the corresponding eigenvalue of a disjoint union of two equal disks, for Robin parameters in $[-4π,4π]$. This sharp inequality was known previously only for negative parameters in $[-4π,0]$, by Girouard and Laugesen. Their proof fails for positive Robin parameters because the second eigenfunction on a disk has non-monotonic radial part. This difficulty is overcome for parameters in $(0,4π]$ by means of a degree-theoretic approach suggested by Karpukhin and Stern that yields suitably orthogonal trial functions.
title Two disks maximize the third Robin eigenvalue: positive parameters
topic Spectral Theory
url https://arxiv.org/abs/2501.15029