# Chaos in networks of coupled oscillators with multimodal natural frequency distributions

## TL;DR

This paper investigates the emergence of chaos in networks of coupled oscillators modeled by the Kuramoto model with multimodal natural frequency distributions, identifying conditions under which chaos occurs or is prevented.

## Contribution

It introduces a collective coordinate reduction approach to analyze chaos in multimodal Kuramoto models and clarifies the role of cluster synchronization and desynchronization.

## Key findings

- Chaos requires at least four clusters for three degrees of freedom.
- Intermittent desynchronization can induce chaos in trimodal distributions.
- Chaos cannot occur in bimodal distributions, even with asymmetry.

## Abstract

We explore chaos in the Kuramoto model with multimodal distributions of the natural frequencies of oscillators and provide a comprehensive description under what conditions chaos occurs. For a natural frequency distribution with $M$ peaks it is typical that there is a range of coupling strengths such that oscillators belonging to each peak form a synchronized cluster, but the clusters do not globally synchronize. We use collective coordinates to describe the inter- and intra-cluster dynamics, which reduces the Kuramoto model to $2M-1$ degrees of freedom. We show that under some assumptions, there is a time-scale splitting between the slow intracluster dynamics and fast intercluster dynamics, which reduces the collective coordinate model to an $M-1$ degree of freedom rescaled Kuramoto model. Therefore, four or more clusters are required to yield the three degrees of freedom necessary for chaos. However, the time-scale splitting breaks down if a cluster intermittently desynchronizes. We show that this intermittent desynchronization provides a mechanism for chaos for trimodal natural frequency distributions. In addition, we use collective coordinates to show analytically that chaos cannot occur for bimodal frequency distributions, even if they are asymmetric and if intermittent desynchronization occurs.