described solely by its phase, with amplitude variations neglected; the oscillators were coupled all-to-all, with equal strength; the interaction between them was purely sinusoidal, with no higher harmonics; and their intrinsic frequencies were randomly distributed across the population according to a symmetric bell-shaped distribution. All of these simplifying assumptions helped Kuramoto make headway on what would otherwise have been a hopelessly intractable many-body, nonlinear dynamical system. By means of an ingenious self-consistency argument, he was able to show analytically that the system could undergo a phase transition to mutual synchronization, once the coupling between the oscillators exceeded a certain threshold.

Over the past three decades, many researchers have shed light on the mathematical aspects of collective synchronization by studying Kuramoto’s model and its close relatives \[Strogatz 2000, Acebron et al. 2005\]. And, somewhat surprisingly in view of its simplicity, the model has also been shown to be relevant to a variety of physical systems \[Pikovsky et al. 2001, Strogatz 2003\]. Examples range from electrochemical oscillators \[Kiss et al. 2002, 2008\] and Josephson junction arrays \[Wiesenfeld et al. 1996\] to coupled metronomes \[Pantaleone 2002\], collective atomic recoil lasing \[von Cube et al. 2004\], and neutrino flavor oscillations \[Pantaleone 1998\].

One way 