“…[23], [24], [8], [25], [2], [6], [16], and reference therein) and at the level of rigorous mathematical physics (see e.g. [21], [5], [4], [1], [3], [9], [20], [27], [13], [14], [15], and references therein). The common wisdom, following the computation by Dirac of the decay rate in second order time-dependent perturbation theory (the famous Fermi golden rule), or the Wigner-Weisskopf approximation in scattering theory, is that the decay law is exponential.…”