2025/12/07 by Chen, Hang, Wu, Bohan
Mathematics · Computer Science · #Nonlinear Partial Differential Equations #Advanced Mathematical Modeling in Engineering #Numerical methods in inverse problems
paper · doi:10.48550/arxiv.2512.06740
We investigate the overdetermined problem given by Δu=0 in Ω, (∂ u)/(∂ν) =σ1 u on ∂ Ω, |∇ u|=constant on ∂ Ω, where Ω is a connected compact Riemannian surface with smooth boundary ∂ Ω, and σ1 is the first nonzero Steklov eigenvalue of Ω. We prove that this overdetermined problem admits a nontrivial solution if and only if Ω is σ-homothetic to either the flat unit disk or a flat cylinder [-T,T]× S1 for some T≥ T1. This gives a complete answer to the question raised by Payne and Philippin in [Z. Angew. Math. Phys. 42(6), 864-873, 1991] for σ=σ1 and arbitrary surfaces. In particular, we completely characterize compact domains in 2-dimensional space forms for which the overdetermined problem is solvable.