Macroscopic detection of the strong stochasticity threshold in Fermi-Pasta-Ulam chains of oscillators

Abstract

The largest Lyapunov exponent of a system composed by a heavy impurity embedded in a chain of anharmonic nearest-neighbor Fermi-Pasta-Ulam oscillators is numerically computed for various values of the impurity mass $M$. A crossover between weak and strong chaos is obtained at the same value ${\epsilon }_{{}_T}$ of the energy density $\epsilon$ (energy per degree of freedom) for all the considered values of the impurity mass $M$. The threshold $\epsi lon_{_T}$ coincides with the value of the energy density $\epsilon$ at which a change of scaling of the relaxation time of the momentum autocorrelation function of the impurity ocurrs and that was obtained in a previous work ~[M. Romero-Bastida and E. Braun, Phys. Rev. E {\bf65}, 036228 (2002)]. The complete Lyapunov spectrum does not depend significantly on the impurity mass $M$. These results suggest that the impurity does not contribute significantly to the dynamical instability (chaos) of the chain and can be considered as a probe for the dynamics of the system to which the impurity is coupled. Finally, it is shown that the Kolmogorov-Sinai entropy of the chain has a crossover from weak to strong chaos at the same value of the energy density that the crossover value ${\epsilon }_{{}_T}$ of largest Lyapunov exponent. Implications of this result are discussed.

6 pages, 5 figures, revtex4 style

References in corpus (4)

• The origin of diffusion: the case of non chaotic systems
• Lyapunov exponents as a dynamical indicator of a phase transition
• When do tracer particles dominate the Lyapunov spectrum?
• Microscopic chaos from Brownian motion in a one-dimensional anharmonic oscillator chain

Cited by in corpus (4)

• Probing Hamiltonian dynamics by means of the 0-1 test for chaos
• Lyapunov modes in three-dimensional Lennard-Jones fluids
• Macroscopic evidence of microscopic dynamics in the Fermi-Pasta-Ulam oscillator chain from nonlinear time series analysis
• Role of chaos for the validity of statistical mechanics laws: diffusion and conduction