Renormalization of potentials and generalized centers

We generalize the Riesz potential of a compact domain in Rm by introducing a renormalization of the rα−m-potential for α⩽0. 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.