A global synchronization theorem for oscillators on a random graph

TL;DR

This paper establishes a sharper threshold for the probability of connection in Erdős-Rényi random graphs that guarantees almost sure global synchronization of Kuramoto oscillators, improving previous bounds.

Contribution

The authors improve the known threshold for global synchronization in Erdős-Rényi graphs from log(n)/n^{1/3} to log^2(n)/n, providing explicit probability estimates.

Findings

Synchronization occurs with high probability above the threshold

Explicit probability bounds for large networks

Improved theoretical understanding of phase transition in random networks

Abstract

Consider $n$ identical Kuramoto oscillators on a random graph. Specifically, consider \ER random graphs in which any two oscillators are bidirectionally coupled with unit strength, independently and at random, with probability $0\leq p\leq 1$. We say that a network is globally synchronizing if the oscillators converge to the all-in-phase synchronous state for almost all initial conditions. Is there a critical threshold for $p$ above which global synchrony is extremely likely but below which it is extremely rare? It is suspected that a critical threshold exists and is close to the so-called connectivity threshold, namely, $p\sim \log(n)/n$ for $n \gg 1$. Ling, Xu, and Bandeira made the first progress toward proving a result in this direction: they showed that if $p\gg \log(n)/n^{1/3}$, then \ER networks of Kuramoto oscillators are globally synchronizing with high probability as $n\rightarrow\infty$. Here we improve that result by showing that $p\gg \log^2(n)/n$ suffices. Our estimates are explicit: for example, we can say that there is more than a $99.9996\%$ chance that a random network with $n = 10^6$ and $p>0.01117$ is globally synchronizing.