Penetration through a wall: Is it reality?
  A tennis ball is not expected to penetrate through a brick wall since a motion under a barrier is impossible in classical mechanics. With quantum effects a motion of a particle through a barrier is allowed due to quantum tunneling. According to usual theories of tunneling, the particle density decays inside a classical barrier resulting in an extremely slow pentration process. However, there are no general laws forbidding fast motion through classical barriers. The problem addressed is investigation of unusual features o quantum tunneling through a classic static barrier which is at least two-dimensional. Here we show that penetration through such barrier can be not slow. When the barrier satisfies the certain conditions, a regime of quantum lens is possible with formation of caustics. De Broglie waves are reflected from the caustics, interfere, and result in a not small flux from under the barrier. This strongly contrasts to the usual scenario with a decaying under-barrier density. We construct a particular example of fast motion through a classical barrier. One can unexectedly conclude that, in principle, nature allows fast penetration through classical barriers which against common sense. The phenomenon may be responsible for a variety of processes in labs and nature. For example, tunneling in solids may occur with a different scenario, in biophysics and chemistry one can specify conditions for unusual reactions, and evanescent optical waves may strongly change their properties. In condensed matter and cosmic physics there are phenomena with misterious reasons of an energy emission, for instance, gamma-ray bursts. One can try to treat them in the context of fast escape from under some barriers. 
B. Ivlev
quant-ph