Hermitian - non-Hermitian interfaces in quantum theory

Abstract: In the global framework of quantum theory the individual quantum systems seem clearly separated into two families with the respective manifestly Hermitian and hiddenly Hermitian operators of their Hamiltonian. In the light of certain preliminary studies these two families seem to have an empty overlap. In this paper we demonstrate that it is not so. We are going to show that whenever the interaction potentials are chosen weakly nonlocal, the separation of the two families may disappear. The overlaps alias interfaces between the Hermitian and non-Hermitian descriptions of the unitarily evolving quantum system in question may become non-empty. This assertion will be illustrated via a few analytically solvable elementary models.