Phase-locking and critical phenomena in lattices of coupled nonlinear oscillators with random intrinsic frequencies

Abstract

We study phase-locking in a network of coupled nonlinear oscillators with local interactions and random intrinsic frequencies. The oscillators are located at the vertices of a graph and interact along the edges. They are coupled by sinusoidal functions of the phase differences across the edges, and their intrinsic frequencies are independent and identically distributed with finite mean and variance. We derive an exact expression for the probability of phase-locking in a linear chain of such oscillators and prove that this probability tends to zero as the number of oscillators grows without bound. However, if the coupling strength increases as the square root of the number of oscillators, the probability of phase-locking tends to a limiting distribution, the Kolmogorov-Smirnov distribution. This latter result is obtained by showing that the phase-locking problem is equivalent to a discretization of pinned Brownian motion. The results on chains of oscillators are extended to more general graphs. In particular, for a hypercubic lattice of any dimension, the probability of phase-locking tends to zero exponentially fast as the number of oscillators grows without bound. We also consider a less stringent type of synchronization, characterized by large clusters of oscillators mutually entrained at the same average frequency. It is shown that if such clusters exist, they necessarily have a sponge-like geometry.