Figure 1: Schematic representation of the absolute irreversibility in the quench dynamics of Ising model.
From: Scaling Law for Irreversible Entropy Production in Critical Systems
In the forward process, the system is initially at equilibrium with positive spontaneous magnetization, whereas in the backward process the initial equilibrium state has no magnetization. When the coupling J increases across the critical point, the system can have either positive or negative magnetization. The latter case has no corresponding forward path, which results in the absolute irreversibility.
