  We consider the modification of the Cahn-Hilliard equation when a time delay
process through a memory function is taken into account. We then study the
process of spinodal decomposition in fast phase transitions associated with a
conserved order parameter. Finite-time memory effects are seen to affect the
dynamics of phase transition at short times and have the effect of delaying, in
a significant way, the process of rapid growth of the order parameter that
follows a quench into the spinodal region. These effects are important in
several systems characterized by fast processes, like nonequilibrium dynamics
in the early universe and in relativistic heavy-ion collisions.
