Determining both leading coefficient and source in a nonlocal elliptic equation

Abstract

In this short note, we investigate an inverse source problem associated with a nonlocal elliptic equation ${\left(-\nabla \cdot \sigma \nabla \right)}^{s}u=F$ that is given in a bounded open set $\Omega \subset {\mathbb{R}}^n$, for $n\ge 3$ and $0<s<1$. We demonstrate both $\sigma$ and $F$ can be determined uniquely by using the exterior Dirichlet-to-Neumann (DN) map in ${\Omega }_e:={\mathbb{R}}^n\setminus \overline{\Omega }$. The result is intriguing in that analogous theory cannot be true for the local case generally, that is, $s=1$. The key ingredients to prove the uniqueness is based on the unique continuation principle for nonlocal elliptic operators and the reduction from the nonlocal to the local via the Stinga-Torrea extension problem.

10 pages. All comments and suggestions are welcome