- Comment on Fluctuation-dissipation relations in the nonequilibrium critical dynamics of Ising models

Auteur(s): Mayer P., Berthier L., Garrahan J.P., Sollich P.

(Article) Publié: Physical Review E: Statistical, Nonlinear, And Soft Matter Physics, vol. 70 p.018102 (2004)


We have recently shown that in nonequilibrium spin systems at criticality the limit X-infinity of the fluctuation-dissipation ratio X(t,t(w)) for tt(w)1 can be measured using observables such as magnetization or energy [ Phys. Rev. E 68, 016116 (2003) ]. Pleimling argues in a Comment [preceding paper, Phys. Rev. 70, 018101 (2004) ] on our paper that for such observables correlation and response functions are dominated by one-time quantities dependent only on t, and are therefore not suitable for a determination of X-infinity. Using standard scaling forms of correlation and response functions, as used by Pleimling, we show that our data do have a genuine two-time dependence and allow X(t,t(w)) and X-infinity to be measured, so that Pleimling's criticisms are easily refuted. We also compare with predictions from renormalization-group calculations, which are consistent with our numerical observation of a fluctuation-dissipation plot for the magnetization that is very close to a straight line. A key point remains that coherent observables make measurements of X-infinity easier than the traditionally used incoherent ones, producing fluctuation-dissipation plots whose slope is close to X-infinity over a much larger range.

Commentaires: English Letter Part 2 844CV