Aging in ferromagnetic systems at criticality near four dimensions

TL;DR

This paper investigates the off-equilibrium dynamics and fluctuation-dissipation ratio in ferromagnetic systems near criticality, providing universal scaling functions and analyzing aging behavior at first order in epsilon expansion.

Contribution

It offers a first-order epsilon expansion analysis of off-equilibrium response and correlation functions in ferromagnetic models near four dimensions, highlighting universal aging properties.

Findings

Universal scaling functions for response and correlation are derived.

A non-trivial fluctuation-dissipation ratio limit is identified in the aging regime.

Results are obtained at criticality and in the high-temperature phase.

Abstract

We study the off-equilibrium response and correlation functions and the corresponding fluctuation-dissipation ratio for a purely dissipative relaxation of an O(N) symmetric vector model (Model A) below its upper critical dimension. The scaling behavior of these quantities is analyzed and the associated universal functions are determined at first order in epsilon expansion in the high-temperature phase and at criticality. A non trivial limit of the fluctuation-dissipation ratio is found in the aging regime.