Interaction of discrete breathers with thermal fluctuations

Discrete breathers (DBs) are time-periodic and spatially localized lattice excitations, which can be linearly stable or unstable with respect to either localized or extended perturbations. We analyze the interaction of DBs with a thermalized background of small-amplitude lattice excitations in a one-dimensional lattice of Morse oscillators with nearest-neighbor interaction. We find that stable DBs are barely influenced by the thermal noise. Unstable DBs are starting to propagate through the lattice, without losing their localization character. The instability can be due to localized perturbations as well as to extended perturbations. We discuss these observations in terms of resonances of DBs with localized and delocalized perturbations, and relate them to the issue of DB impact on the statistical properties of nonlinear lattices.