Beyond the classical limit: Correlation effects in the chaotic masermodel

We derive the classical limit of the nonintegrable Maser model as a unitary approximation to the exact dynamical evolution of quantum subsystems. We next construct a short time expansion of the evolution of quantum correlations and extract analytical information from the physics which dictates the characteristic time of validity of the classical approximation. We find the rather surprising result that nonintegrable contributions are essential to produce long-lasting classical states.