Note on energy index and first eigenvalue of minimal surfaces in spheres

Fuente: arXiv
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Autore principale: Gianocca, Matilde
Natura: Preprint
Pubblicazione: 2025
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author Gianocca, Matilde
author_facet Gianocca, Matilde
contents A minimal immersion from a surface to $S^3$ can be viewed both as a critical point of the area and of the energy. Although no difference appears at first order, looking at the respective second variations unveils significant differences. It is well known that whenever the first eigenvalue satisfies $λ_1(Σ)\geq2$, the index is $\mathrm{ind}_E(Σ)\leq 4$. The converse implication is much more subtle. We prove that whenever $λ_1(Σ)<\frac{1}{6}$, there exists a vector field $X$, orthogonal to the four Möbius vector fields, with negative second variation. We also prove an arbitrary codimension version of this statement: any immersed minimal surface $Σ\subset S^n$ with first eigenvalue $λ_1(Σ)<\frac{n-2}{2n}$ admits a vector field $X$ orthogonal to the $n+1$ Möbius fields with negative second variation.
format Preprint
id arxiv_https___arxiv_org_abs_2510_11811
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Note on energy index and first eigenvalue of minimal surfaces in spheres
Gianocca, Matilde
Differential Geometry
53A10, 58E20
A minimal immersion from a surface to $S^3$ can be viewed both as a critical point of the area and of the energy. Although no difference appears at first order, looking at the respective second variations unveils significant differences. It is well known that whenever the first eigenvalue satisfies $λ_1(Σ)\geq2$, the index is $\mathrm{ind}_E(Σ)\leq 4$. The converse implication is much more subtle. We prove that whenever $λ_1(Σ)<\frac{1}{6}$, there exists a vector field $X$, orthogonal to the four Möbius vector fields, with negative second variation. We also prove an arbitrary codimension version of this statement: any immersed minimal surface $Σ\subset S^n$ with first eigenvalue $λ_1(Σ)<\frac{n-2}{2n}$ admits a vector field $X$ orthogonal to the $n+1$ Möbius fields with negative second variation.
title Note on energy index and first eigenvalue of minimal surfaces in spheres
topic Differential Geometry
53A10, 58E20
url https://arxiv.org/abs/2510.11811