paper

Mean curvature bounds and eigenvalues of Robin Laplacians

arXiv:1407.3087 · doi:10.1007/s00526-015-0850-1

Abstract

We consider the Laplacian with attractive Robin boundary conditions, \[ Q^Ω_αu=-Δu, \quad \dfrac{\partial u}{\partial n}=αu \text{ on } \partialΩ, \] in a class of bounded smooth domains ; here is the outward unit normal and is a constant. We show that for each and , the th eigenvalue has the asymptotics \[ E_j(Q^Ω_α)=-α^2 -(ν-1)H_\mathrm{max}(Ω)\,α+{\mathcal O}(α^{2/3}), \] where is the maximum mean curvature at . The discussion of the reverse Faber-Krahn inequality gives rise to a new geometric problem concerning the minimization of . In particular, we show that the ball is the strict minimizer of among the smooth star-shaped domains of a given volume, which leads to the following result: if is a ball and is any other star-shaped smooth domain of the same volume, then for any fixed we have for large . An open question concerning a larger class of domains is formulated.

15 pages

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