Mixtures and pure states in relativistic Schrödinger theory

Abstract

In relativistic Schrodinger theory, a physical system can be described by a wave function (↝ “pure state”) or by an intensity matrix (↝ “mixture”). Since the space-time evolution of the system is described by anon-Hermitian Hamiltonian, transmutations of mixtures into pure states (and vice versa) would be formally possible. Nevertheless, the transition of a mixture into a pure state is dynamically forbidden, whereas the pure states are unstable and decay into mixtures. This effect is demonstrated by considering the Klein-Gordon-Higgs equations over an expanding Robertson-Walker universe.