“…Please note that in the stating of this theorem, we have tacitly assumed that the potential V (x), p and the initial data z 0 belong to a class in which a unique solution of the initial-value problem for (1.1) exists for all t ∈ [0, T * ) and some T * < ∞ or T * = ∞. In view of local well-posedness results for this kind of problems studied by Lange-Poppenberg [9] and the arguments developed by Cazenave [5], we will continue to make these assumptions without any comments. Moreover, if z 0 is radially symmetrical with respect to x, then so is z(x, t).…”