Role of initial state and final quench temperature on aging properties in phase-ordering kinetics

We study numerically the two-dimensional Ising model with nonconserved dynamics quenched from an initial equilibrium state at the temperature Ti≥Tc to a final temperature Tf below the critical one. By considering processes initiating both from a disordered state at infinite temperature Ti=∞ and from the critical configurations at Ti=Tc and spanning the range of final temperatures Tf[0,Tc [we elucidate the role played by Ti and Tf on the aging properties and, in particular, on the behavior of the autocorrelation C and of the integrated response function χ. Our results show that for any choice of Tf, while the autocorrelation function exponent λC takes a markedly different value for Ti=∞ [λC(Ti=∞)≃5/4] or Ti=Tc [λC(Ti=Tc)≃1/8] the response function exponents are unchanged. Supported by the outcome of the analytical solution of the solvable spherical model we interpret this fact as due to the different contributions provided to autocorrelation and response by the large-scale properties of the system. As changing Tf is considered, although this is expected to play no role in the large-scale and long-time properties of the system, we show important effects on the quantitative behavior of χ. In particular, data for quenches to Tf=0 are consistent with a value of the response function exponent λχ=12λC(Ti=∞)=5/8 different from the one [λχ(0.5-0.56)] found in a wealth of previous numerical determinations in quenches to finite final temperatures. This is interpreted as due to important preasymptotic corrections associated to Tf>0.