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Mathematical Model Unravels the Complexity of Synchronicity

Six planes flying in synchroneity.
Credit: Joshua Brown / Unsplash.
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Computer scientists and mathematicians at the University of Sydney and Max Planck Institute study synchronization in complex systems, revealing insights into network structures' impact on various applications, from power grids to the brain.

Key takeaways

    • Researchers at the University of Sydney and the Max Planck Institute developed methods to understand synchronization in complex systems, like human dancing or neural activity.
    • Their research focuses on network structures connecting elements, revealing insights into designing interventions in systems, including stabilizing power grids and preventing epileptic seizures.
    • The study's main finding highlights that networks with more convergent walks tend to have poorer synchronization, shedding light on brain dynamics and social network phenomena.

    Synchronised phenomena are all around us

    Computer scientists and mathematicians working in complex systems at the University of Sydney and the Max Planck Institute for Mathematics in the Sciences in Germany have developed new methods to describe what many of us take for granted – how easy, or hard, it can be to fall in and out of sync.

    Synchronised phenomena are all around us, whether it is human clapping and dancing, or the way fireflies flash, or how our neurons and heart cells interact. However, it is something not fully understood in engineering and science.

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    Associate Professor Joseph Lizier, expert in complex systems at the University of Sydney, said: “We know the feeling of dancing in step to the ‘Nutbush’ in a crowd – or the awkward feeling when people lose time clapping to music. Similar processes occur in nature, and it is vital that we better understand how falling in and out of sync actually works.

    “Being in sync in a system can be very good; you want your heart cells to all beat together rather than fibrillate. But being in sync can also be very bad; you don’t want your brain cells to all fire together in an epileptic seizure.”

    Associate Professor Lizier and colleagues at the Max Planck Institute in Leipzig, Germany have published new research on synchronisation in the Proceedings of the National Academy of Sciences of the United States of America (PNAS).

    The paper sets out the mathematics of how the network structure connecting a set of individual elements controls how well they can synchronise their activity. It is a critical insight into how these systems operate, because in most real-world systems, no one individual element controls all the others. And nor can any individual directly see and react to all the others: they are only connected through a network.

    Associate Professor Lizier, from the Centre of Complex Systems and the School of Computer Science in the Faculty of Engineering, said: “Our results open new opportunities for designing network structures or interventions in networks. This could be super useful in stabilising electricity in power grids, vital for the transition to renewables, or to avoid neural synchronisation in the brain, which can trigger epilepsy.”

    To understand how these systems work, the researchers studied what are known as “walks” through a network in a complex system. Walks are sequences of connected hops between individual elements or nodes in the network.

    Associate Professor Lizier said: “Our maths examines pair­ed walks: where you start at one node and set off on two walks with randomly chosen hops between nodes for a specified number of steps. Those two walks might end up at the same node (convergent walks) or at different nodes (diverg­­­­ent walks).

    “Our main finding is that the more commonly paired walks on a network are convergent, the worse the quality of synchronisation on that network structure would be.”

    This is good news for the brain, where synchronisation is not desirable as it can cause epilepsy . The brain’s highly modular structure means it has a high proportion of convergent walks, which naturally push it away from epilepsy.

    “We can even draw an analogy to social media with the echochamber phenomenon,” said co-author Jürgen Jost, whose group also works on social network dynamics. “Here we see sub-groups reinforcing their own messages, via convergent walks within their own group, but not necessarily synchronising to the wider population.”

    The findings represent a major step forward in the theory of how the structure of complex networks affects their dynamics or how they compute, such as how brain structure underpins cognition.

    Reference: Lizier JT, Bauer F, Atay FM, Jost J. Analytic relationship of relative synchronizability to network structure and motifs. Proc Natl Acad Sci USA. 2023;120(37):e2303332120. doi: 10.1073/pnas.2303332120

    This article has been republished from the following materials. Article summaries may have been generated by fact-checked AI models. Note: material may have been edited for length and content. For further information, please contact the cited source.