  We study the time evolution of entangled states of a pair of identical atoms,
considered in the harmonic approximation, coupled to an environment represented
by an infinite set of free oscillators, with the whole system confined within a
spherical cavity of radius $R$. Taking the center-of-mass and the
relative-position coordinates, and using the dressed-state approach, we present
the time evolution of some quantities measuring the entanglement, for both
limits of a very large and a small cavity; the chosen examples are simple and
illustrate these very distinct behaviors.
