A Spectral Characterization Of Geodesic Balls In Non-Compact Rank One Symmetric Spaces

TL;DR

This paper proves that in non-compact rank one symmetric spaces, geodesic balls uniquely maximize the first Steklov eigenvalue for fixed volume, extending Euclidean results, and explores stability and limitations of this property.

Contribution

It extends the characterization of geodesic balls as maximizers of the first Steklov eigenvalue to non-compact rank one symmetric spaces and establishes a stability version of this inequality.

Findings

Geodesic balls uniquely maximize the first Steklov eigenvalue in non-compact rank one symmetric spaces.

A stability version of the Brock-Weinstock inequality is established.

Geodesic balls are not global maximizers on the standard sphere.

Abstract

In constant curvatures spaces, there are a lot of characterizations of geodesic balls as optimal domain for shape optimization problems. Although it is natural to expect similar characterizations in rank one symmetric spaces, very few is known in this setting. In this paper we prove that, in a non-compact rank one symmetric space, the geodesic balls uniquely maximize the first Steklov eigenvalue among the domains of fixed volume, extending to this context a result of Brock in the Euclidean space. Then we show that a stability version of the ensuing Brock-Weinstock inequality holds. The idea behind the proof is to exploit a suitable weighted isoperimetric inequality which we prove to hold true, as well as in a stability form, on harmonic manifolds. Eventually we show that, in general, the geodesic balls are not global maximizers on the standard sphere.