  An analytically solvable model for quasi-static transformations across
quantum critical points featuring Bosonic quasi-particle excitations is
presented. The model proves that adiabaticity breakdown is a general feature of
universal slow dynamics in these systems. The existence of an "anti-adiabatic"
dynamical phase with vanishing ground state fidelity in the slow drive limit is
also proven. The relation of these findings with the Kibble-Zurek mechanism and
their consequences on defect formation in many body systems ramped across a
quantum phase transition are discussed.
