Stages of Energy Transfer in the FPU Model

The Alpha version of the Fermi-Pasta-Ulam problem is revisited through direct numerical simulations and an application of weak turbulence theory. The energy spectrum, initialized with a large scale excitation, is traced through a series of distinct qualitative phases en route to eventual equipartition. Weak turbulence theory is applied in an attempt to provide and effective quantitative description of the evolution of the energy spectrum. Some scaling predictions are well-confirmed byt the numerical simulations.