A Subtlety of the Schr\"{o}dinger Picture Dynamics
  We address a mathematical and physical status of exotic (like e.g. fractal) wave packets and their quantum dynamics. To this end, we extend the formal meaning of the Schr\"{o}dinger equation beyond the domain of the Hamiltonian. The dynamical importance of the finite mean energy condition is elucidated. 
Piotr Garbaczewski