Wave propagation in a generalized Minkowski space and superluminal signals

Tunnelling of wavepackets at velocities higher than the light speed in vacuum finds a natural explanation in the framework of a generalization of special relativity, in which nonlocal interactions are described in an effective way by means of a deformation of the usual Minkowski metric. This picture can be considered as an effective description of virtual particles (propagating with imaginary classical wavevector in the usual spacetime) as objects which propagate in the deformed Minkowski space with a new, but real, wavevector. Our formalism is explicity applied to the superluminal propagation of electromagnetic evanescent waves in waveguides. We propose also an experimental setup, based on light propagation in optical fibers, which may provide a new optical test of e.m. superluminal tunneling.