Lyapunov Modes for a Nonequilibrium System with a Heat Flux

We present the first numerical observation of Lyapunov modes (mode structure of Lyapunov vectors) in a system maintained in a nonequilibrium steady state. The modes show some similarities and some differences when compared with the results for equilibrium systems. The breaking of energy conservation removes a zero exponent and introduces a new mode. The transverse modes are only weakly altered but there are systematic changes to the longitudinal and momentum dependent modes.