The supertasks described by Perez Laraudogoitia, involving the dynamics of a system containing an infinite number of particles in a bounded region of space, are characterized by the nonconservation of energy and by the spontaneous motion of particles. We argue that these features arise from the inadequacy of the local, particle-by-particle description used to analyze the supertasks. A global analysis, involving embeddings in Hilbert spaces, clarifies these supertasks and avoids what we regard as their nonphysical features.

In two recent papers Perez Laraudogoitia has described a variety of supertasks involving elastic collisions in Newtonian systems containing a denumerably infinite set of particles. He maintains that these various supertasks give examples of systems in which energy is not conserved, particles at rest begin to move spontaneously, particles disappear from a system, and particles are created ex nihilo. An analysis of these supertasks suggests that they involve systems that do not satisfy the mathematical conditions required of Newtonian systems at (...) the time the supertask is due to be completed, or else they rely on the application of the time-reversal transformation to states which are not well-defined. Consequently, it is unjustified to conclude that the paradoxical results are arising from within the framework of Newtonian mechanics. In the last part of this article, we discuss various aspects of the physics of these supertasks. (shrink)