Chaotic Breathers in a Nonlinear Beam Lattice Model

Dynamical behaviours of chaotic breathers are investigated numerically for a one-dimensional nonlinear beam lattice model involving rotational degree of freedom in addition to the well-known FermiPasta-Ulam-β (FPU-β) lattice. Evolutions of the initial disturbances composed of the highest wavenumber mode are pursued numerically to observe generation, propagation, and an eventual decay of the localized structure (chaotic breather). Detailed numerical analyses are done for the FPU-β lattice so as to compare with the beam lattice model. Initial localization process is discussed based on the modulational instability theory. Dynamical evolutions of displacemment, rotation, energy, wavenumber spectra etc. are observed and an attempt is made to understand qualitatively the entire evolution process. It is found that the inclusion of the rotation enhances either generation or decay processes of the chaotic breathers in comparison with the case of the FPU-β lattice.