A non-Boltzmannian behavior of the energy distribution for quasi-stationary regimes of the Fermi–Pasta–Ulam image system Original Research Article

In a recent paper [M. Leo, R.A. Leo, P. Tempesta, C. Tsallis, Phys. Rev. E 85 (2012) 031149], the existence of quasi-stationary states for the Fermi–Pasta–Ulam image system has been shown numerically, by analyzing the stability properties of the image-mode exact nonlinear solution. Here we study the energy distribution of the modes image, image and image, when they are unstable, as a function of image and of the initial excitation energy. We observe that the classical Boltzmann weight is replaced by a different weight, expressed by a image-exponential function.