  We generalize the Riesz potential of a compact domain in $\mathbb{R}^{m}$ by
introducing a renormalization of the $r^{\alpha-m}$-potential for $\alpha\le0$.
This can be considered as generalization of the dual mixed volumes of convex
bodies as introduced by Lutwak. We then study the points where the extreme
values of the (renormalized) potentials are attained. These points can be
considered as a generalization of the center of mass. We also show that only
balls give extreme values among bodied with the same volume.
