  It is shown that the Lorentz transformation cannot in general be formally
applied to potentials and fields of particles locked in a certain region. In
particular, this property relates to nucleons in nuclei and to particles and
nuclei in storage rings. Even if they move with high velocities, their electric
fields are defined by the Coulomb law. The result obtained is rather important
for the planned deuteron electric-dipole-moment experiment in storage rings.
