  The concept of quantum revivals is extended to many-body systems and the
implications of traversing a quantum phase transition are explored. By
analyzing two different models, the vibron model for the bending of polyatomic
molecules and the Dicke model for a quantum radiation field interacting with a
system of two-level atoms, we show evidence of revival behavior for wave
packets centered around energy levels as low as the fundamental state. Away
from criticality, revival times exhibit smooth, nonsingular behavior, and are
proportional to the system size. Upon approaching a quantum critical point,
they diverge as a power law and scale with the system size, although the
scaling is no longer linear.
