System Size Stochastic and Coherence Resonance

We demonstrate that in ensembles of noise‐driven dynamical systems a maximum order can appear at a certain system size, while the noise and coupling remain constant. We discuss two situations with system size resonance. In the first one an ensemble of coupled nonlinear noisy oscillators demonstrates in the thermodynamic limit an Ising‐type transition. When a small periodic force acts on the ensemble in the ordered phase, the linear response of the system has a maximum at a certain system size. Next, we show that in an ensemble of coupled noise‐driven FitzHigh‐Nagumo oscillators a maximum coherence of the output mean field occurs at a definite ensemble size.