A spontaneous symmetry breaking mechanism is investigated in a conformally coupled massless, γσ 4 model in a spatially flat Robertson-Walker univrse by relaxing the requirement of conformal time translation invariance on the ground state and the one-loop effective action is conputed for the appropriate time-dependent background field. The infrared behavior of the model requires a modification of the propagator. A finite renormalized trace anomaly is isolated which yields a dynamical equation for the expansion scale factor.