  This paper is concerned with quantum dynamics of a system coupled to a
critical reservoir. In this context, we employ the Dicke model which is known
to exhibit a super radiant quantum phase transition (QPT) and we allow one of
the mirrors to move under a linear restoring force. The electromagnetic field
couples to the movable mirror though radiation pressure just like in typical
optomechanical setups. We show that, in the thermodynamical limit, the
super-radiant phase induces a classical driving force on the mirror without
causing decoherence.
