Fermi Problem and Superluminal Signals in Quantum Electrodynamics

Using as an example the Fermi problem dealing with nonstationary transformation of optical excitation from one atom to another the reason of superluminal signals appearance in quantum electrodynamics is clearing. It is shown that the calculation using the conventional methods in Heisenberg and Schrödinger representations in nonstationary problems lead to different results. The Schrödinger representation predicts the existents of specified quantum superluminal signals. In Heisenberg representation the superluminal signals are absent. The reason of non-identity of representations is close connected with using of the adiabatic hypothesis.