In $\mathbb R^{n\geq3}$, spheres can be characterized by single layer potentials having constant eigenfunction. More precisely we have the following:
Theorem (H. Shahgholian) Let $\Omega\subset \mathbb R^{n\geq3}$ be a bounded smooth domain and for some $c>0$
$$\int_{\partial\Omega}\frac{1}{\|x-y\|^{n-2}}ds_x=\frac{c}{\|y\|^{n-2}},\,\,\forall y\not\in\bar{\Omega}$$ Then $\partial\Omega$ is a sphere centered at the origin. (here $ds$ represents the surface area).
Are there generalization of this statement for Riemannian manifolds and geodesic balls?