![]() ![]() In the momentum space, the effect is understood as a bandwidth phenomenon, where more » the incident pulse probes local, rather than global, analytical properties of the transmission amplitude T(p). Causality ensures that none of the constituent envelopes are advanced with respect to free propagation, yet the resulting pulse is advanced due to a peculiar interference effect, similar to the one responsible for ‘anomalous’ values which occur in Aharonov’s ‘weak measurements’. In the coordinate representation, a barrier is shown to act as an effective beamsplitter, recombining envelopes of the freely propagating pulse with various spacial shifts. We analyse in detail the reshaping mechanism leading to apparently ‘superluminal’ advancement of a wave packet traversing a classically forbidden region. It is argued that analyzing apparent 'superluminality' in terms of spacial displacements helps avoid contradiction associated with time parameters such as the phase time. The complex shift, given by the first moment of the DAD, accounts for both the displacement of the maximum of the transmitted probability density and the increase in its velocity. In the case of a wide barrier, initial envelope is accurately translated into the complex coordinate plane. ![]() = function, the transmission amplitude is superoscillatory for finite momenta and more » tunneling leads to an accurate advancement of the (reduced) initial envelope by the barrier width. ![]()
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