Discrete breathers in transient processes and thermal equilibrium

We study four different aspects of the generation of discrete breathers in one-(1D) and two-dimensional (2D) lattices with soft and hard nonlinearity. Breathers can be generated in thermal equilibrium and in various transient and nonequilibrium situations. We use the numerically obtained information about the spatio-temporal evolution of nonlinear lattices and combine it with analytical and heuristic results and arguments on breather existence, stability and interaction with plane waves to provide with a coherent picture of the complex nature of breather excitation in nonlinear lattices.