A.B. Klimov, L. Roa and I. Sainz
JOURNAL OF PHYSICS A-MATHEMATICAL AND THEORETICAL 41, 35 (2008)
An effective Hamiltonian describing interaction between generic fast and slow systems is obtained in the strong interaction limit. The result is applied for studying the effect of quantum phase transition as a bifurcation of the ground state of the slow subsystem. Examples such as atom-field and atom-atom interactions are analyzed in detail.