In the framework of Fermi theory, nonstationary β -decay is considered. In order to simplify the calculations, the theory omits the accounting of antineutrino and neglects the presence of spin in the particles. The electron is called the mezon. Specifically, the non-stationary process of meson exchange between the neutron and the proton at the final distance from it, which turns proton into a neutron as a result of such exchange, is considered. The calculations are performed both in Schrödinger representation and Heisenberg representation. Schrödinger presentation shows that the meson resulting from the neutron emission can be absorbed by the proton at the final distance from the emitter before the light needs to cover this distance. This quantum effect with the superluminal transmission of information is in dissonance with the classical theory, which does not allow particles of finite mass to possess speeds even close enough to the speed of light in vacuum. Calculations in Heisenberg representation of the existence of superluminal signals do not allow. The non-equivalence of Heisenberg and Schrödinger representations in non-stationary quantum mesodynamics, known in electrodynamics, is stated. The preference is given to Schrödinger representation with reference to an experiment that numerically confirms the presence of superluminalsignals in electrodynamics.