Uniqueness and symmetry of minimizers of Hartree type equations with external Coulomb potential

In a recent paper, Georgiev and Venkov establish first radial symmetry and then uniqueness of minimizers to a certain functional. In the present paper we prove first the uniqueness of possible positive minimizers by revealing a hidden convexity property of the underlying functional. Then symmetry follows from the simple observation that uniqueness fails if there is a nonradial minimizer, because it could be rotated and give rise to a second minimizer