Damage spreading in the Ising model with a microcanonical constraint

We study damage spreading in the ferromagnetic Ising model, on the square lattice, by performing numerical simulations in the microcanonical ensemble. Although the damage spreads for all temperature values, a dynamical critical phenomenon is observed at Td=1.020(2)TC (TC is the Curie temperature): For T{≥}Td the damage D(t) is insensitive to its initial value D(0), while for TTd a weak dependence on D(0) is present in such a way that for each T there are two values of D(t) corresponding to the initial conditions D(0)1/2 and D(0)>1/2. We have also identified a convenient order parameter to characterize the transition occurring at Td. {} 1996 The American Physical Society.