Dynamical quasidegeneracies and separation of regular and irregular quantum levels

Abstract

Dynamical quasidegeneracies may arise in the spectrum of systems having discrete symmetries. They are semiclassically interpreted as quantized congruent but distinct tori in phase space. With them the separation of regular and irregular states in the quantum spectrum of some mixed phase-space systems may be performed in a simple yet clear fashion. At finite energies (h finite), the frontier between regular and irregular states is not sharp. This is illustrated by the study of two coupled quartic oscillators.