Thermalization of a Coupled Oscillator Chain

Coupled pendula show complex and unpredictable collective motions and provide a suitable physical model for complex dynamical systems. Starting from the well-known Fermi- Pasta-Ulam experiment coupled oscillators are expected to undergo spontaneous thermalization, typical of multi-body systems with non-linear interactions, and have been studied in order to investigate energy equipartition and second principle of thermodynamics. By means of an automated videotracking apparatus we have monitored both single and collective motions occurring in a chain of 24 non-linearly coupled pendula on varying the initial conditions (anharmonicity level, number and energy of excited pendula, etc.). Compared to the original FPU model our chain is highly and quickly dissipative and thermalizes very early. Moreover, we have observed other noticeable phenomena as, e.g., l oscillation asymmetry and intrinsic localized modes.