On the spectrum of a Hamiltonian defined on su_q(2) and quantum optical   models
  Analytical expressions are given for the eigenvalues and eigenvectors of a Hamiltonian with su_q(2) dynamical symmetry. The relevance of such an operator in Quantum Optics is discussed. As an application, the ground state energy in the Dicke model is studied through su_q(2) perturbation theory. 
Angel Ballesteros and Sergei M. Chumakov