Entropy production, energy dissipation and violation of Onsager relations in the steady glassy state
In a glassy system different degrees of freedom have well-separated characteristic times, and are described by different temperatures. The stationary state is essentially non-equilibrium. A generalized statistical thermodynamics is constructed and a universal variational principle is proposed. Entropy production and energy dissipation occur at a constant rate; there exists a universal relation between them, valid to leading order in the small ratio of the characteristic times. Energy dissipation (unlike entropy production) is closely connected to the fluctuations of the slow degree. Corrections due to a finite ratio of the times are obtained. Onsager relations in the context of heat transfer are also considered. They are always broken in glassy states, except close to equilibrium.