LYAPUNOV SPECTRUM OF THE DRIVEN LORENTZ GAS

A method for the evaluation of the full Lyapunov spectrum of an externally driven system with a hard-core interaction is presented. It is applied to the periodic Lorentz gas subjected to a homogeneous held and coupled to a Gaussian thermostat. The algorithm treats both the intercollisional streaming and the hard-core collisions exactly and can be easily generalized to many-body systems in nonequilibrium steady states interacting with hard-core potentials. From the Lyapunov spectrum of the Lorentz gas, the information dimension and the associated dimensionality reduction of the underlying fractal attractor were determined and compared to independent box-counting estimates for the same quantities.