THE CLASSICAL ANALOG OF THE SUPERRADIANT PHASE-TRANSITION IN THE DICKE-MODEL

We construct the classical analogue of the phenomena of super-radiance in the zero temperature limit and show that a simple geometrical interpretation can be given in the integrable case. The non-integrable case is also studied and in both cases we find bifurcation of equilibrium for the same parameter values where this phase transition is known to occur in the thermodynamical context. The ground state of the system is also studied in the framework of a mean field approximation and a simple analytical expression obtained. A connection between the classical and quantum points of view is presented.