Abstract:
We define a proper effective temperature for relativistic nonequilibrium steady states (NESSs).
A conventional effective temperature of NESSs is defined from the ratio of the fluctuation to the
dissipation. However, NESSs have relative velocities to the heat bath in general, and hence the
conventional effective temperature can be frame-dependent in relativistic systems. The proper
effective temperature is introduced as a frame-independent (Lorentz-invariant) quantity that
characterizes NESSs. We find that the proper effective temperature of NESSs is higher than
the proper temperature of the heat bath in a wide range of holographic models even when the
conventional effective temperature is lower than the temperature of the heat bath.
