Simulation algorithms for multidimensional nonlinear response of classical many-body systems

The numerical effort and convergence of equilibrium and nonequilibrium (finite field) techniques for simulating the response of classical systems to a sequence of n short pulses are examined. The former is recast in terms of n point correlation functions and nth order stability matrices which contain higher order generalized Lyapunov exponents, whereas the latter involves sums over perturbed trajectories. The two methods are tested for a highly chaotic system: The Lorentz gas, and for the less chaotic quartic oscillator. (C) 2003 American Institute of Physics.