Thomas Jüngling

Stochastic switching in delay-coupled oscillators

A delay is known to induce multistability in periodic systems. Under influence of noise, coupled oscillators can switch between coexistent orbits with different frequencies and different oscillation patterns. For coupled phase oscillators we reduce the delay system to a nondelayed Langevin equation, which allows us to analytically compute the distribution of frequencies and their corresponding residence times. The number of stable periodic orbits scales with the roundtrip delay time and coupling strength, but the noisy system visits only a fraction of the orbits, which scales with the square root of the delay time and is independent of the coupling strength. In contrast, the residence time in the different orbits is mainly determined by the coupling strength and the number of oscillators, and only weakly dependent on the coupling delay. Finally we investigate the effect of a detuning between the oscillators. We demonstrate the generality of our results with delay-coupled FitzHugh-Nagumo oscillators.

Synchronization of Heterogeneous Oscillators by Noninvasive Time-Delayed Cross Coupling.

We demonstrate that nonidentical systems, in particular, nonlinear oscillators with different time scales, can be synchronized if a mutual coupling via time-delayed control signals is implemented. Each oscillator settles on an unstable state, say a fixed point or an unstable periodic orbit, with a coupling force which vanishes in the long time limit. We present the underlying theoretical considerations and numerical simulations, and, moreover, demonstrate the concept experimentally in nonlinear electronic oscillators.

On the Interplay of Noise and Delay in Coupled Oscillators

Coupling delays can play an important role in the dynamics of various networks, such as coupled semiconductor lasers, communication networks, genetic transcription circuits or the brain. A well established effect of a delay is to induce multistability: In oscillatory systems a delay gives rise to coexistent periodic orbits with different frequencies and oscillation patterns. Adding noise to the dynamics, the network switches stochastically between these delay-induced orbits. For phase oscillators, we compute analytically the distribution of frequencies, the robustness to noise and their dependence on system parameters as the coupling strength and coupling delay.