  Even though the Bohmian trajectories given by integral curves of the
conserved Klein-Gordon current may involve motions backwards in time, the
natural relativistic probability density of particle positions is well-defined.
The Bohmian theory predicts subtle deviations from the statistical predictions
of more conventional formulations of quantum theory, but it seems that no
present experiment rules this theory out. The generalization to the case of
many particles or strings is straightforward, provided that a preferred
foliation of spacetime is given.
