Effects of an external drive on the fluctuation-dissipation relation of phase-ordering systems

TL;DR

This paper investigates how an external shear flow affects the fluctuation-dissipation relation in phase-ordering systems, revealing distinct stationary and aging behaviors and their dependence on temperature and time scales.

Contribution

It explicitly analyzes the fluctuation-dissipation relation in a large-N model under shear flow, extending understanding of non-equilibrium stationary and aging regimes.

Findings

Non-trivial fluctuation-dissipation relation in high-temperature phase

Explicit splitting of autocorrelation into stationary and aging parts

Aging response becomes negligible as waiting time increases

Abstract

The relation between the autocorrelation $C(t,t_w)$ and the integrated linear response function $\chi(t,t_w)$ is studied in the context of the large-N model for phase-ordering systems subjected to a shear flow. In the high temperature phase $T>T_c$ a non-equilibrium stationary state is entered which is characterized by a non-trivial fluctuation-dissipation relation $\chi (t-t_w)=\tilde \chi(C(t-t_w))$. For quenches below $T_c$ the splitting of the order parameter field into two statistically independent components, responsible for the stationary $C^{st}(t-t_w)$ and aging $C^{ag}(t/t_w)$ part of the autocorrelation function, can be explicitly exhibited in close analogy with the undriven case. In the regime $t-t_w\ll t_w$ the same relation $\chi (t-t_w)=\tilde \chi (C^{st}(t-t_w))$ is found between the response and $C^{st}(t-t_w)$, as for $T>T_c$ . The aging part of $\chi (t,t_w)$ is negligible for $t_w\to \infty$, as without drive, resulting in a flat $\chi (C)$ in the aging regime $t-t_w\gg t_w$.