Instabilities in classical and quantum fluids

A formal analysis of the time evolution of the one-particle momentum distribution is introduced to demonstrate that runaway solutions, violating the conservation of momentum, occur when non-central pair potentials are used in classical systems. It is suggested that the problem is resolvable by including internal degres of freedom. Similarly, when non-Hermitean Hamiltonians are introduced in quantum systems, runaway behavior is also found. These suspected instabilities are interpreted to indicate the onset of turbulence and point out the need for new approaches in describing the many-body behaviour of classical systems with non-central pair potentials, and the quantum description of systems with non-Hermitean Hamiltonians. (C) 1998 Elsevier Science B.V.