Weak connections, time scales, and aggregation of nonlinear systems

If nonlinear subsystems with continuous equilibria are weakly connected, their local behavior is fast compared with the system-wide behavior caused by the connections. The slow behavior is described by an aggregate model which appears as a slow subsystem in the singular perturbation form of the model. In this way earlier linear aggregation results by Simon et al. in economics and slow coherency results in power systems are extended to nonlinear systems and related to singular perturbations.