On universality in aging ferromagnets

TL;DR

This paper investigates the universality of out-of-equilibrium critical dynamics in various lattice models by analyzing autocorrelation decay and fluctuation-dissipation ratios after a quench to the critical temperature.

Contribution

It provides a comparative Monte Carlo simulation study of universal quantities across multiple models and lattice geometries at criticality.

Findings

Universal values of autocorrelation decay exponent $mbda/z$ identified.

Asymptotic fluctuation-dissipation ratio $X_$ found to be consistent across models.

Evidence supports universality in out-of-equilibrium aging dynamics.

Abstract

This work is a contribution to the study of universality in out-of-equilibrium lattice models undergoing a second-order phase transition at equilibrium. The experimental protocol that we have chosen is the following: the system is prepared in its high-temperature phase and then quenched at the critical temperature $T_c$. We investigated by mean of Monte Carlo simulations two quantities that are believed to take universal values: the exponent $\lambda/z$ obtained from the decay of autocorrelation functions and the asymptotic value $X_\infty$ of the fluctuation-dissipation ratio $X(t,s)$. This protocol was applied to the Ising model, the 3-state clock model and the 4-state Potts model on square, triangular and honeycomb lattices and to the Ashkin-Teller model at the point belonging at equilibrium to the 3-state Potts model universality class and to a multispin Ising model and the Baxter-Wu model both belonging to the 4-state Potts model universality class at equilibrium.