Periodic travelling wave solutions of discrete nonlinear Schr\"odinger equations

The existence of nonzero periodic travelling wave solutions for a general discrete nonlinear Schr\"odinger equation (DNLS) on finite one-dimensional lattices is proved. The DNLS features a general nonlinear term and variable range of interactions going beyond the usual nearest-neighbour interaction. The problem of the existence of travelling wave solutions is converted into a fixed point problem for an operator on some appropriate function space which is solved by means of Schauder's Fixed Point Theorem

Existence and congruence of global attractors for damped and forced integrable and nonintegrable discrete nonlinear Schr\"odinger equations

We study two damped and forced discrete nonlinear Schr\"odinger equations on the one-dimensional infinite lattice. Without damping and forcing they are represented by the integrable Ablowitz-Ladik equation (AL) featuring non-local cubic nonlinear terms, and its standard (nonintegrable) counterpart with local cubic nonlinear terms (DNLS). The global existence of a unique solution to the initial value problem for both, the damped and forced AL and DNLS, is proven. It is further shown that for sufficiently close initial data, their corresponding solutions stay close for all times. Concerning the asymptotic behaviour of the solutions to the damped and forced AL and DNLS, for the former a sufficient condition for the existence of a restricted global attractor is established while it is shown that the latter possesses a global attractor. Finally, we prove the congruence of the restricted global AL attractor and the DNLS attractor for dynamics ensuing from initial data contained in an appropriate bounded subset in a Banach space

Exponentially stable breather solutions in nonautonomous dissipative nonlinear Schr\"odinger lattices

We consider damped and forced discrete nonlinear Schr\"odinger equations on the lattice $\mathbb{Z}$. First we establish the existence of periodic and quasiperiodic breather solutions for periodic and quasiperiodic driving, respectively. Notably, quasiperiodic breathers cannot exist in the system without damping and driving. Afterwards the existence of a global uniform attractor for the dissipative dynamics of the system is shown. For strong dissipation we prove that the global uniform attractor has finite fractal dimension and consists of a single trajectory that is confined to a finite dimensional subspace of the infinite dimensional phase space, attracting any bounded set in phase space exponentially fast. Conclusively, for strong damping and periodic (quasiperiodic) forcing the single periodic (quasiperiodic) breather solution possesses a finite number of modes and is exponentially stable

Self-organized escape processes of linear chains in nonlinear potentials

An enhancement of localized nonlinear modes in coupled systems gives rise to a novel type of escape process. We study a spatially one dimensional set-up consisting of a linearly coupled oscillator chain of $N$ mass-points situated in a metastable nonlinear potential. The Hamilton-dynamics exhibits breather solutions as a result of modulational instability of the phonon states. These breathers localize energy by freezing other parts of the chain. Eventually this localised part of the chain grows in amplitude until it overcomes the critical elongation characterized by the transition state. Doing so, the breathers ignite an escape by pulling the remaining chain over the barrier. Even if the formation of singular breathers is insufficient for an escape, coalescence of moving breathers can result in the required concentration of energy. Compared to a chain system with linear damping and thermal fluctuations the breathers help the chain to overcome the barriers faster in the case of low damping. With larger damping, the decreasing life time of the breathers effectively inhibits the escape process.Comment: 14 pages, 13 figure