Super-radiant dynamics, doorways and resonances in nuclei and other open mesoscopic systems

Abstract

The phenomenon of super-radiance (Dicke effect, coherent spontaneous\nradiation by a gas of atoms coupled through the common radiation field) is well\nknown in quantum optics. The review discusses similar physics that emerges in\nopen and marginally stable quantum many-body systems. In the presence of open\ndecay channels, the intrinsic states are coupled through the continuum. At\nsufficiently strong continuum coupling, the spectrum of resonances undergoes\nthe restructuring with segregation of very broad super-radiant states and\ntrapping of remaining long-lived compound states. The appropriate formalism\ndescribing this phenomenon is based on the Feshbach projection method and\neffective non-Hermitian Hamiltonian. A broader generalization is related to the\nidea of doorway states connecting quantum states of different structure. The\nmethod is explained in detail and the examples of applications are given to\nnuclear, atomic and particle physics. The interrelation of the collective\ndynamics through continuum and possible intrinsic many-body chaos is studied,\nincluding universal mesoscopic conductance fluctuations. The theory serves as a\nnatural framework for general description of a quantum signal transmission\nthrough an open mesoscopic system.\n