  By considering the Langevin dynamics of the SK spin glass with a spherical
constraint we calculate the asymptotic distance between two real replicas that
evolve with the same thermal noise from different initial conditions. Despite
the simplicity of the model its dynamics is known to be non trivial and
presents aging phenomena. We find that the asymptotic distance between two
replicas is maximal for a whole family of initial conditions that are
arbitrarily close at t=0 . The asymptotic distance presents a dynamical
transition at a temperature equal to the static phase transition one.
