# An Inverse Problem for an Elliptic Equation

### Robert Dalmasso

Equipe EDP, Grenoble, France

## Abstract

We consider the following overdetermined boundary value problem: ∆_u_ = −λ_u_−µ in Ω, *u* = 0 on ∂Ω and ∂_u_/∂_n_ = ψ on ∂Ω, where λ and µ are real constants and Ω is a smooth bounded planar domain. A very interesting problem is to examine whether ∂_u_ one can identify the constants λ and µ from knowledge of the normal ﬂux ∂_n_ on ∂Ω corresponding to some nontrivial solution. It is well known that if Ω is a disk then such identiﬁcation of (λ, µ) is completely impossible. Some partial results have already been obtained. The purpose of this paper is to extend and to improve these results. Moreover we also examine the interesting case where ψ is constant.

## Cite this article

Robert Dalmasso, An Inverse Problem for an Elliptic Equation. Publ. Res. Inst. Math. Sci. 40 (2004), no. 1, pp. 91–123

DOI 10.2977/PRIMS/1145475967