All superparticles are BPS

Abstract

The generic action for an N-extended superparticle in D-dimensional Minkowski spacetime is shown to have 'hidden' supersymmetries (related by 'dualities' to the manifest supersymmetries) such that the full supersymmetry algebra is BPS-saturated; the exceptions (which include, trivially, the massless case) are those for which the manifest supersymmetry algebra is already BPS-saturated. Moreover, it is shown that any 'non-BPS' superparticle action is a gauge-fixed version of the 'BPS' superparticle action for which all supersymmetries are manifest. An example is the N = 1 massive D = 10 superparticle, which actually has N = 2 supersymmetry and is equivalent to the action for a D0-brane of IIA superstring theory.