Out of Equilibrium Temperature from Holography
Introduction — Unlike equilibrium systems, which are under powerful constraints of thermodynamics, only few general properties are known for systems driven far out of equilibrium. In this paper, we use the holographic principle to define an effective temperature for a class of nonequilibrium steady states and study its properties. We consider branes driven by external energy sources and put them in a heat bath. The heat bath is represented by a bulk geometry with an event horizon. The Hawking temperature at the horizon is identified as the temperature T of the heat bath. Before we turn on the external energy sources, temperature on the brane is the same as that of the bulk. Holographically, this can be seen by the fact that the induced metric on the brane has an event horizon with the same Hawking temperature T.