Violation of the Fluctuation Dissipation Theorem during Domain Growth in the Long-range Ising Model

The celebrated {\it fluctuation dissipation theorem} (FDT) does not apply to nonequilibrium systems. In this context, Cugliandolo and Kurchan [Phys. Rev. Lett. {\bf 71}, 173 (1993)] introduced a generalized FDT which interprets the nonequilibrium evolution as a composition of {\it time sectors} corresponding to different {\it effective temperatures}. We use this framework to study domain growth in the $d=2$ long-range Ising model (LRIM) with nonconserved kinetics ({\it Glauber spin-flip}) and conserved kinetics ({\it Kawasaki spin-exchange}). We study the dynamical scaling and super-universal (SU) scaling of various two-time quantities, e.g., autocorrelation function, response function, effective temperature, etc. In particular, we investigate how the interaction range and conservation laws affect these characteristic features of domain growth.

Parbati Saha, Sanjay Puri, Varsha Banerjee · 2025