SPECTRUM-GENERATING SYMMETRIES FOR BPS SOLITONS

We show that there exist non-linearly realised duality symmetries that are independent of the standard supergravity global symmetries, and w hich provide active spectrum-generating symmetries for the fundamental BPS solitons. The additional ingredient, in any space-time dimension, is a single scaling transformation that allows one to map between BPS solitons with different masses. Without the inclusion of this additio nal transformation, which is a symmetry of the classical equations of motion, but not the action, it is not possible to find a spectrum-gene rating symmetry. The necessity of including this scaling transformatio n highlights the vulnerability of duality multiplets to quantum anomal ies. We argue that fundamental BPS solitons may be immune to this thre at. (C) 1998 Published by Elsevier Science B.V.