BARRIER PENETRATION AND SUPERLUMINAL VELOCITY

We show rigorously in a causal theory that a gaussian wave packet, incident from the left on a potential barrier, turns up on the right side of the barrier at an earlier time than would appear to be allowed by causal propagation. A sufficient set of conditions on the wave packet and barrier parameters for this phenomenon to take place is given. These conditions are quite restrictive but may not all be necessary. There is, of course, only an apparent violation of causality. © 1993 Academic Press, Inc.